Suppressing electron-phonon coupling and energy loss in organic solar cells by modulating donor-acceptor penetrated-interface

Domain: physics
Published: 2026-01-26
Editorial outcome: major_revision

Abstract
Organicsolarcells(OSCs)achieve21%efficiency,yetnon-radiativeenergyloss(qΔV nr)remainsacriticalbarriertofurtherimprovetheopen-circuitvoltage(V OC).ThislossisprimarilygovernedbytheoptoelectronicpropertiesofinterfacialCTstates,yetthepreciseroleofelectron-phononcoupling(EPC)isnotfullyresolved.Throughanalysisofthreeall-polymerOSCsandfoursmallmoleculeacceptor(SMA)-basedOSCs,weidentifytwodonor-acceptor(D-A)interfacialmixedphasesthatfostertwodistinctCTstates,establishingefficientchargegeneration.ThesetwophasesemergefromamorphousD-Aentanglement,termedasEntangled(E-)interface,andthepenetrationofacceptorquasi-aggregatesintodonorpolymermatrix,termedasPenetrated(P-)interfaces.TheP-interfaceexhibitsinherentlyweakerEPCthanthatofE-interfacesincethesuppressedintramolecularinteraction.Astheresults,theP-interfaces,governingall-polymerOSCs,achieveasignificantreductionof~60meVinqΔV nrcomparedtoE-interfacedominatedSMA-basedOSCs.TheincorporationofPAintoSMAsystemasguestcomponentmodulatesthepopulationofP-interfacereducingtheEPCandthenenhancingV OC.Overall,ourworksuggeststhatmodulatingthepopulationofP-interfacestosuppressEPCisaviablestrategyforreducingnon-radiativevoltagelossandovercomingtheefficiencybottleneckoforganicsolarcells.

Introduction
State-of-the-artNFAbasedsystems,suchasPM6-Y6,achievedhighV OC(>0.85V)despiteminimalenergyoffsets(drivingforce)betweentheenergyofexcitedsingletstate(E S1)andchargetransfer(CT)state(E CT),denotedasΔE S1-CT.Thesesystemsmaintainover90%chargegenerationefficiency,challengingthetwo-statemodelthatpredictsalargeΔE S1-CTisnecessarytominimizeqΔV nr.Toaddressthisdiscrepancy,Nelsonetal.andGaoetal.proposedathree-statemodelemphasizingthe role of S-CT hybridization and thermalpopulation. Thismodelintroduces the concept of intensity borrowing from the high-oscillator-strength E S1, which enhanced the luminescence of the CT stateandreducetheqΔV nr,as1–4:

ΔV nr = (k B T / q) ln (k r / (β k r + k nr)) (1)

Here,theexternalelectroluminescencequantumefficiency(EQE EL)ofdevices is determined by the radiative (k r) and non-radiative (k nr) recombinationrateconstants,andtheout-couplingfactor(β)ofthedevice,assumedtobe0.21,5.OneguidelineforreducingΔV nr involvesenhancingtheS 1 andCTstateshybridizationforimprovingCTstateemissionbyintensityborrowmechanism.Therefore,thenatureofCTstatesshouldbediscussedcarefully6.Additionally,thecoexistenceofmultiple interfacial CT states in recent BHJ systems has introduced diversechargegenerationpathways7.Salleoetal.andAmassianetal.directlylinkNFAblendmorphologyandstructuralorder/disordertoMulti-CTstatesdistributionsandassociatednon-radiativerecombination process via systematic compositional tuning8–11. Despite these advances,themechanisticunderstandingofhowinterfacialCTstatesgovernchargegenerationdynamicsremainsincomplete,particularlyin emerging polymer donor-polymer acceptor (PD-PA) systems. Moreover, definitive morphological signatures identifying specific interfacialarchitecturesandcorrespondingCTstatesarelacking.

Asidefromthoseelectronicproperties,electron-phonon(vibrational)coupling(EPC)ofCTstateshasreceivedlimitedattention.EPCcharacterizestheinterplaybetweenmoleculargeometrydeformationsandelectrontransferprocesses12.Specifically,itdescribesthedegreeofexcitons,CTexcitons(CTEs),andpolaronsundergophononscattering,subsequentlydissipatingabsorbedenergyasheatfromlatticevibrationthroughnon-radiative decay pathways prior to charge separation and collection13–15. The strong EPC leads to rapid non-radiative decay, a well-documented limitation in fullerene-basedOSCs16,17. Minimizing EPC is thus a promising strategy to suppress non-radiative recombination and reduce voltage losses18,19. Approachessuchasenhancingorbitaldelocalization16,whichismorecommonin polymer acceptor than small molecular acceptors, or employing moleculardesignstrategies,includingtheintroductionofnoncovalentinteraction between NFAs non-rigid end group20, asymmetric side chaininNFAspromotingthemoreplanarskeleton21,andsolidadditivetoplanarizethelatticevibration15,havebeenshowntolowerEPC.Jenetal.utilizedHuang–Rhysfactor(S)toquantifytheEPCofY6as1.07andintroducedthedilutedstrategytoreducetheEPCandΔV nr22,23. Nevertheless, most EPC studies have focused on pure phases and materials,leavingtheinfluenceofEPCatcomplicatedD-Ainterfaces,where exciton dissociation and charge generation occur, largely unexplored.

Inthiswork,weinvestigattwoemergingPD-NFAsystems,PD-SMA systemandPD-PAsystem,withcontrastingaggregationbehaviorsthatgovern their bulk heterojunction (BHJ) optical and morphological landscapes.ByanalyzingfourPD-SMAsystemandthreePD-PAsystem,thePD-SMAsystemstendtoformhigh-purityacceptordomainsanddisordered mixed phases, whereas the PD-PA systems exhibit a reversed morphology comprising disordered pure domains but orderedintermixedphases,consistentwithpreviousfindingsbyChowetal.24.Weuncoverdistinctphaseevolutionpathwaysundercompositionalvariation11,25. SMA systems undergo rapid phase separation, whilethePAsystemsexhibitgradualtransitionsfromthefullyamorphous phase (Entangled (E)-interface), to the quasi-aggregates and penetratedpolymerchainfilledphase(Penetrated(P)-interface),andultimatelytothecrystallinepurephase.TheP-interfaceexhibitslightedge-onmolecularorientationrelativetothepureacceptordomains.Critically,time-dependentdensityfunctionaltheory(TD-DFT)calculationsandexperimentalresultsconfirmthatsuchP-interfacesexhibitintrinsicallyweakerEPCcomparedtodisorderedE-interfaces26. Besides,P-interfacesalsofacilitatesefficientchargegeneration,asseenfrom the kinetics of P-interface dominated PA systems. In performance,simulated energy lossanalysisreveals thattheselow-EPCP-interfacesreducenon-radiativeenergylossesby~58meV,aligningwithexperimental reduction of energy loss (~55meV) of PA system. The achieved V OC increase in PA-SMA ternary system (D18-PY-IT-eC9) supports the strategy to modulate the population of P-interface by incorporationPAintoSMAsystem.ThisworknotonlyidentifiesthecharacteristicsofP-interfaces butalsoelucidates theP-interfacesasmultifunctional interfacial architectures that both suppress voltage lossesandenhancechargegeneration.Thesefindingsoffervaluabledesign principles, specifically highlighting the importance of optimizingP-interfaceformationtoenhancetheperformanceoforganicsolarcells(OSCs).

Results
Basicopticalpropertiesandenergylevelalignment
Figure1ashowsthechemicalstructuresofpolymerdonors(PDs)D18andPM6,smallmolecularacceptors(SMAs)eC9andY6,andpolymeracceptors (PAs) PY-IT and PY-DT. All of the D-A combinations have been widely used in high-efficiency SMA-based and all-polymerorganicsolarcells(OSCs)27.Theenergylevelsfortherepresentators,D18 (PD), eC9 (SMA), and PY-IT (PA) are determined by ultraviolet Photoemission Spectroscopy (UPS) and the intersection of the normalized absorption and photoluminescence (PL) spectra (Fig. 1b, c, Supplementary Figs. S1, S2)28. The HOMO level and E g are nearlyidentical for PA (−5.45eV, ~1.5eV) and SMA (−5.45eV, ~1.48eV), differingbyonly~20meVinE g (SupplementaryFigs.S1,S2).DeconvolutionofneatPLspectrarevealsamorepronounceddisorderedphaseinPAthanSMA,consistentwithPA’sstrongerintermixingtendency(Supplementary Fig. S3)6. To examine optical property evolution, blend films are prepared with the compositional variations of D-A ratios, 10-1, 10-2, 10-5, 10-10 and 10-15. Increasing acceptor concentrationinducesaredshiftinbothabsorptionandPLspectra.ThisshiftissignificantlylargerinSMA-basedblends(~51meVfrom10-1to10-15)thaninPA-basedblends(~11meV),reflectingstrongerelectronicinteractionsinSMA systems (Supplementary Figs. S4, S5, Supplementary Table S1)29. These spectral shifts may arise from order-to-disorderphasetransitions,whicharemoreprominentinSMA-basedblends.Atlowacceptorconcentrations,filmscompriseprimarilydisordered domains with intermixed D-A interfaces11. Higher acceptor concentrationspromoteorderedpuredomains,causingtheobservedredshifts (Supplementary Fig. S6). The pronounced shifts in SMA blendssuggestenhancedintermolecularcouplingfromintrinsicSMAself-aggregation, amplifying contrasts between disordered andorderedphases30.Incontrast,minimalPAshiftsimplythatintra-chainwavefunction delocalization yields intrinsicallysmaller E g 24. We performthein-situspectroelectrochemistry(SEC)measurement,thein-situ cyclicvoltammetry with UV-vis-NIR spectroscopy,to determine the energy level of interface under different D-A ratio31–33. By comparison, the disordered phase (interface) exhibits shallower HOMO depththanthepureacceptor(representedbypristineacceptor)andsmallerΔHOMOdifference(ΔHOMO) between donor and acceptor, indicatingauphillenergylandscapetransitionfrompuredomaintointerface,alsosupportingbythedeconvolutionofUPSspectra(Supplementary Figs. S7–S11)6,34,35. Interestingly, the PA system shows continuouslyshallowedΔHOMO,whichmightlinktothemorphologyevolution32. Notably, increasing acceptor ratios amplifies energetic orderinbothinPAandSMAsystemasthegrowthoforderedpuredomain.ThelargerUrbachenergy(E urbach)inSMAsystematlowD-AratioindicatesmoredisorderedphasethanPAsystem(SupplementaryFig.S12)36.However,mappingtheenergylandscapesofthesesystemsremain challenging due to unclarified electronic properties of D-A interfaces,thecriticalsitesforexcitondissociationandchargegeneration. Given the substantial impact of interfacial properties on device performance, systematic investigation of these interfaces is essentialforfurtheroptimization.

Themorphologyevolutionofentangled-andpenetrated-interfaceinblends
Togaindeeperinsightintotheinterfacialmorphologyoftheblends,we characterized miscibility and phase behavior. As shown in SupplementaryTableS2andSupplementaryFig.S13,thePD-PAblendexhibits a smaller Flory-Huggins interaction parameter (χ) than PD-SMA.Thisindicatesstrongerthermodynamicmiscibilityandenhanceddonor–acceptorpercolationattheinterfaceinPA-basedblends.Weemploy grazing-incidence wide and small-angle X-ray scattering (GIWAXSandGISAXS)toanalyzemolecularpackinganddomainsize,focusingoninterfacialmorphology(SupplementaryFigs.S14–S19)37.Astheacceptorratioincreased,SMAblendsdeveloptightermolecularpacking(smallerd-space)andthelongercrystalcoherentlength(CCL)inbothlamellarandπ-πstacking(SupplementaryFig.S20a).PAblends exhibitextendedCCLintwotypesofstackingbutlooserπ-πstackingdue to PA’s inherently less compact structure (Supplementary Fig.S20b).ThesetrendssuggestthatSMAfavorscrystalline,tightlypacked pure domains, whereas strong interfacial percolation in PA promoteslargerintermixeddomainsandlooserpuredomains.Thisis furthercorroboratedbytheFlory-Hugginstwo-phasediagram,whichshowsahigherD-Aratiothresholdforthe1-phaseto2-phasetransitioninPAsystems(SupplementaryFig.S21)24,38.

We now turn to stacking orientation preference by extracting scattering intensity distribution, revealing the increased face-on orientation with higher acceptor ratio. The edge-on/phase-on ratio (A z/A xy)forlamellarstackingincreases(SupplementaryFig.S22),andthepeakwidth(FWHMπ-π)offace-onπ-πstackingnarrows(Fig.2a,b)39.Additionally,theevolutionofHerman’sOrientationparameter(H)confirmsthesametrends,transitionfromedge-ontoface-onorientation,supportingbytheHUMO(IE)levelshiftingmeasuredfromin-situSEC(Fig.2a,b,SupplementaryFigs.S9,S22,andSupplementaryNoteS1)40.This phase transition can also be observed from charge transport mobility evolution both in In-plane (IP) and out-of-plane(OOP)directionmeasuredfromOFETandOPVdevices(SupplementaryFig.S24).ThedetailedcomparisonsofFWHMπ-π,A z/A xyratioandHparameterrevealthatSMAsystemtransitfromedge-ontoface-onpackingrapidlyandsignificantlyatlowD-Aratio(H 10-1 =−0.23toH 10-5 =0.7), stabilizing later (H 10-15 =0.79). In contrast, the PA system transitionsgradually.Notably,atlowratioof10-1,thebroaderFWHMπ-πinSMAsystemmaydonatethemoredisorderednatureofintermixregioninSMAsystem.Wequantifiedintermixed(isotropic)regionsbytheintermixfactor(Λ),which,inbrief,describedtheratioofintermixscatteringintensityto total scattering intensity (Supplementary Note S1). The larger Λ in PA system (Λ 10-15 =0.18, Fig. 2a) signifies retained intermixed phase, while lower Λ in SMA reflects greater crystallization(Λ 10-15 =0.07,Fig.2b).

Atlowacceptorratios(10-1and10-2),bothPAandSMAsystemsinitiallyformentangledamorphousregionsbutminimalpureacceptorregions.Subsequently,pureregionsinSMAsystemgrowsrapidlyuntilreachingathresholdratioof10-5andthenstabilizes,whereasthePAsystemundergoesasteadygradualtransition.Thisstepwiseevolutionunderscoresthetransitionsfromintermixedregiontopuredomainsinbothsystems.Thedifferencebetweentherelativedegreeofcrystalline(rDoC) of actual and expected lamellar (ΔrDoC) of blends demonstrates the presenceof lamellar order inintermixregion, similar to previousobservation(Fig.2c,SupplementaryFigs.S25,S26)11.Therefore,akeyprogresswithintransitionistheformationofshort-rangeaggregatesofamorphousacceptor(quasi-aggregates),whichcreatesaspecial quasi-aggregated intermix region, containing the interfacial characteristics.TheweakermiscibilityofSMAwithPDleadstoweakpercolation, constraining the growth of quasi-aggregates but promotingthegrowthofpureregion24,41.Incontrast,thestrongerinterfacialpercolationinthePAsystempromoteslargerquasi-aggregatedintermixregionandmorerobustpolymernetworkforcharge transport(Fig.2c)42.The quasi-aggregates in intermixregion canbeuniformly observed across representative seven OPV systems (Supplementary Figs. S25–S27). Here, we clarified the entangled amorphous regions and quasi-aggregated regions as two distinct interfaces:(1)TheEntangled-interface(E-interface),afullyamorphous(isotropic)regionwheredonorandacceptorarecompletelyentangled(cautiously modeled by the feature of 10-1 D-A ratio); and (2) The Penetrated-interface (P-interface), formed by the crystallized quasi-aggregates(short-rangeaggregatesofamorphousacceptor)andthosepenetratedPDchains(cautiouslymodeledbythefeatureof10-15D-A ratio).ThesedistinctionselucidatethestructuralevolutionofphaseseparationacrossdifferentD-Acompositionsandsystems.Inparticular, PA system exhibits a gradual transition from the amorphous E-interfacetothedominatedquasi-orderedP-interface,andultimatelytotheorderedcrystallinepurephase.WeproposetoutilizeΔrDoCtoqualitativelydeterminethepopulationofP-interface.Asaresults,PAsystem presents a more substantial P-interface population (larger ΔrDoC).Insharpcontrast,therapidtransitionofSMAsystemindicatesthelimiteddevelopmentofbothE-andP-interface(smallΔrDoC),withthe dominated former. We suspect that the formation of isolated acceptorunits(ortinyclusters)inisotropicintermixregionmaylead to the deep traps at E-interface, while the formation of short-rangeinterfacequasi-aggregatesatP-interfacemaysupressthosedeeptraps,whichpromotetheenergeticorder43,44.

Asestablished,excitonsdissociateintocharge-transfer(CT)statesand then separate into free carriers at interfaces, underscoring the crucialneedtodifferentiatethemorphologyofE-andP-interfacesinboth PA and SMA systems45,46. We quantitatively analyze the non-crystalline ring associated with the interface (in the range of 1.2–1.5A−1).GiventheamorphousnatureoftheE-interface,wehypothesizethatthispackingfeaturecontributestothequasi-crystallineP-interface.Thus, we analyze the morphology of the P-interface by deconvolutingIPscatteringintensities,especiallyfocusingonedge-onorientation (detail see Supplementary Fig. S28). The edge-on ratio (intensityratioofquasi-aggregatesandlamellarstacking)inthePAandSMAsystem(Fig.2d)followsthetransitionaltrendsthegrowthoftheP-interface.ThisobservationindicatesthattheP-interface,whilestilllimited,exhibitsamarginallygreaterdegreeofedge-onfeaturesthan theamorphousE-interface.Thecomparativelymoreapparentedge-oncharacteristicsareobservedinthePAsystem,cautiouslysupportingbyhigherelectronmobilityanditsfasterevolutioninOFETdevices(Fig.2d,SupplementaryFig.S24).WeproposethecrossingstructureforP-interfaceexhibitingunalignedandtiltedpackingbetweendonorand acceptor, and the parallel structure for E-interface with better molecularalignment(SupplementaryFig.S29).Notably,weemphasise thatalthoughtheP-interfaceexhibitsmorepronouncededge-onfeatures than pure phase, it is still significantly dominated by face-on orientation.

We, subsequently, performed GISAXS measurements to determine the size of the intermix region (ξ interface), containing both E-interface and P-interface, and the crystalline pure domain (2R g-Acceptor)(seeSupplementaryNoteS1)39.ThesizesoftheintermixdomainsdecreaseandthepuredomainincreasewithincreaseofD-Aratio. PA system shows larger interface domain, while SMA system shows larger pure domain (Supplementary Fig. S30), aligning with GIWAXSresults,indicatingstrongerpreferenceofforminginterfaceinPAsystems.Overall,thesemorphologicalresultsconfirmtheexistence of the P-interface in both the PA and SMA systems.The PA system exhibitsthemorepronouncedP-interfacewithmoreobviousedge-onfeaturesandlargerintermixdomainsthantheSMAsystem.Incontrast,the P-interface in the SMA system evolves more rapidly despite its lowerpopulation.ThesedistinctmorphologiessignificantlyinfluencetheoptoelectronicpropertiesofCTstates,whichcanbeestimatedbytheoreticalsimulationandcalculation47.

Theoreticalsimulationandcalculation
According to the results of molecular dynamics simulation, we observed that the donor and acceptor molecules exhibit different stackingarrangementsdependingonthelarge-scalemolecularorganization.Foranalyticalclarity

Methods

Peer review rounds
[{"round": 1, "reviewer_comments": {"reviewer_1": "The authors present a potential strategy on suppressing non-radiative energy loss in organic solar cells through precise modulation of donor/acceptor penetrated interfaces. The combination of morphological analysis, charge carrier dynamics, and photophysical modeling offers new insights into the role of interfacial heterogeneity in governing charge-transfer (CT) state dynamics and, thereby, voltage loss. While the study presents a compelling case for tuning penetrated interfaces to suppress non-radiative losses, a more detailed mechanistic understanding, particularly in quantitatively classifying interfacial types and identifying their respective contributions to non-radiative loss, would further strengthen the work. Also, several critical issues should be addressed prior to publication:\n1.The authors claim that the P-interface is dominant in polymer-based systems. However, to the best of my knowledge, this concept has not been reported in previous literature. How can the authors justify that this assumption is valid across all polymer systems?\n2.“...... disordered phases exhibit higher energy levels and shallower HOMO depths than ordered domains, also confirming by our UPS measurements” The authors suggest that energy levels differ between ordered and disordered domains, supported by UPS. However, UPS typically probes the average occupied density of states at the film surface. The levels of the individual materials tell nothing about the level alignment when they contact. UPS needs to be measured on the two materials in contact to claim the HUMO level differences.\n3.For the electron-phonon interaction ,this is a crucial physical process in organic materials, crucial for charge recombination. The authors should provide a systematic discussion of this aspect,\n4.The decomposition of GIWAXS in-plane scattering into donor, acceptor, and quasi-aggregated contributions is insightful. However, the physical basis for introducing a quasi-aggregate component—distinct from donor/acceptor neat contributions—should be better justified. How to understand the quasi-aggregate component? Will these aggregated free molecules arise the electron trap due to the large LUMO offset between donor and acceptor? What is the difference between the polymer acceptor and small molecular acceptor?\n5.The manuscript introduces two distinct types of donor-acceptor interfaces, the Entangled-interface (E-interface) and Penetrated-interface (P-interface), based on morphological features at different D:A ratios. While this is a valuable conceptual framework, the criteria for assigning these identities could benefit from further clarification. Specifically, what is the quantitative threshold for defining the interface of organic solar cell systems as E- or P-type, or even the parameter to help people quantify the categories and concentration of interface? Is it based on a certain level of crystalline, FWHM values, or intermix factor (Λ)? Including a more systematic or continuous metric (e.g., an interface order index) would increase the robustness and generalizability of this classification scheme.\n6.“This observation indicates that the P-interface possesses more pronounced edge-on features than either the amorphous E-interface or the pure domains (dominated by face-on orientation).” The authors state that the transition from edge-on to face-on packing is convincingly demonstrated using FWHM, Az/Axy, and Herman’s parameter. However, the recent discussion is all focus on morphology without the implications of these orientation shifts on electronic processes, particularly charge transport across or along the interface, are not fully articulated. It would be better to test the charge transport mobility, especially the transport at in-plane direction, to confirm the transition.\n7.The author fitted CT state properties by only EL spectra, differing from the common practice of co-fitting sEQE and EL. What is the justification for using only EL? How does this approach compare in accuracy or applicability to co-fitting methods?\n8.“In the SMA system, the CTEs population is larger than those in SMA system” appears to be a typo and creates confusion.\n9.The conclusion that EPC is stronger at interfaces of SMA system than PA system is drawn from the D18:PYIT and D18:eC9 systems. Would this trend hold for other donor-acceptor pairs, or is it specific to these materials?\n10.For recent small energy offset systems, please discuss the contribution to ΔVnr from other parameters such as reorganization energy and electronic couplings under the effects of reduced EPC. Can the relative contributions of these factors be estimated or decoupled?\n11.The discussion emphasizes that introducing a ternary component promotes P-interfaces, yet provides no metric or descriptor for how this structural change is quantified or inferred.\n12.The exciton lifetime kinetics in Fig. S36 appear to be influenced by the instrument response functon(IRF). Moreover, the authors analyze charge generation on timescales much faster than that shown in Fig. S36. It is recommended to conduct TRPL measurements with a shorter time resolution and correlate those results to the charge generation process.", "reviewer_2": "The manuscript by Luo et al. investigates the role of penetrated donor-acceptor (D:A) interfaces in modulating electron–phonon coupling (EPC) and its impact on energy loss in organic solar cells (OSCs). The authors strategically employ a combination of a polymer acceptor and a small molecule acceptor with D18 as the donor in varying ratios of acceptors to tune the D:A interface morphology. Two interfacial configurations, designated as E-interface and P-interface, are identified using various X-ray scattering techniques and supported by transient absorption spectroscopy (TAS). EPC is further explored through theoretical calculations, and its relationship to voltage loss is discussed.\nWhile the study provides an alternative perspective on D:A interface morphology and its influence on voltage loss, the manuscript suffers from significant complexity and lacks a clear narrative. The core findings are diluted by the inclusion of extraneous data and overly intricate analyses, which obscure the primary message. Below are several major concerns that need to be addressed:\n1. The transition from edge-on to face-on molecular packing at the D:A interface—induced by varying the acceptor-to-donor ratio—likely alters the interfacial energetics beyond changes in the optical bandgap. These energetic shifts are critical to understanding voltage losses but are not directly measured or discussed. A more accurate assessment could be achieved using in-situ cyclic voltammetry (CV) combined with absorption spectroscopy to estimate the energy levels and offsets at the D:A interface. (Energy Environ. Sci., 2024, 17, 6676-6697)\n2. The assignment of the CT-state emission appears problematic. The manuscript reports CT emission that is blue-shifted relative to the local excitation (LE) emission of the low-bandgap component, which contradicts the fundamental understanding that CT states typically lie below LE states. This discrepancy raises concerns about the accuracy of the spectral deconvolution or the identification of the emissive states. The authors must revisit this analysis with greater care.\n3. While analyzing non-radiative voltage losses across different blend ratios (10:1 to 10:15 for EC9 and PYIT), the authors do not account for the potential impact of LE-CT energy offset changes or hybridization effects. These factors are known to contribute significantly to voltage loss and should be included in the discussion or analysis.\n4. At low acceptor concentrations (e.g., 10:1), the device is heavily donor-rich (D18-dominant). Given D18 known as high photoluminescence quantum yield and documented EQEEL values of ~1.23% DOI: [10.1038/s41467-025-58352-x], it is important to examine whether the increased voltage losses arise from poor electrode work function alignment. Have the authors considered testing alternative device architectures or interlayers to rule out electrode-induced misalignment as a source of loss?\n5. The inclusion of PYIT as a third component reportedly improves the VOC by only ~20 meV. Such a modest enhancement is neither novel nor significant, given the extensive prior literature that has established similar ternary effects and underlying physical mechanisms e.g., DOI: [10.1038/s41560-023-01309-5]. The authors should clarify how this finding advances existing knowledge.\n6. The manuscript is presented as an investigation of EPC and its role in energy loss, as indicated by the title and abstract. However, the majority of the results section is devoted to charge carrier dynamics with little reference to EPC or energy loss mechanisms. If the authors consider the charge dynamics central to the manuscript's message, they should restructure the abstract and Introduction to guide the reader accordingly. Alternatively, the manuscript should be refocused to stay aligned with the stated objective."}, "author_response": "Point-to-point Response to Referees Letter\nThe comments by the reviewers are in black, our responses are in blue, and the changes\nin the main text and supporting information are tracked in red.\nReviewers’ Comments to Authors:\nReviewer #1:\nThe authors present a potential strategy on suppressing non-radiative energy loss in\norganic solar cells through precise modulation of donor/acceptor penetrated interfaces.\nThe combination of morphological analysis, charge carrier dynamics, and\nphotophysical modeling offers new insights into the role of interfacial heterogeneity in\ngoverning charge-transfer (CT) state dynamics and, thereby, voltage loss. While the\nstudy presents a compelling case for tuning penetrated interfaces to suppress non-\nradiative losses, a more detailed mechanistic understanding, particularly in\nquantitatively classifying interfacial types and identifying their respective contributions\nto non-radiative loss, would further strengthen the work. Also, several critical issues\nshould be addressed prior to publication:\nResponse: We thank the reviewer for the positive comments on this work. We have\noutlined our point-by-point responses to the comments/suggestions made by Reviewer\n#1 below.\n1. The authors claim that the P-interface is dominant in polymer-based systems.\nHowever, to the best of my knowledge, this concept has not been reported in previous\nliterature. How can the authors justify that this assumption is valid across all polymer\nsystems?\nResponse: We thank the reviewer for the insightful comments and suggestions. We fully\nagree that the system (D18:PY-IT) we discussed in this manuscript cannot fully\nrepresent the polymer-based systems. While prior studies have, to some extent, implied\nthe presence of amorphous aggregates (or quasi-aggregates) of SMAs within intermix\nregion, they fell short of providing a precise definition for this structure and\nconcurrently linking it to both charge carrier dynamics and energy loss simultaneously\n(Adv. Energy Mater. 2023, 13, 2204297; Nat Commun, 2024, 15, 2784; Energy Environ.\nSci., 2024, 17, 8893-8903). However, as mentioned by reviewer, these studies are\nmostly focused on SMA-based systems but polymer-based. Another work by Chow et.\nal., (Nat Commun, 2024, 15, 1212) reported the much stronger penetration between\npolymer donor (PD) and polymer acceptor (PA) by comparison PY-IT and its another\ntwo derivatives, PYF-T-o and PY-V-y, with Y6. This indicates that PD is able to\npercolate into PA forming more intermix region. Therefore, this manuscript further\ndiscussed the crystalline properties of the more pronounced intermix region formed by\npolymer acceptors.\nTo address the concern of generalizability, we have taken the following measures for\nsupporting our claims. We introduced another PD, PM6, to blend with PY-IT for\nunderstanding the role of P-interface in different PD systems. Besides, we introduced\nPY-DT, which is a derivative of PY-IT, and SMA Y6 to understand the role of P-\ninterface in different PA systems and SMA systems. In results, no matter utilizing PD\n(PM6 and D18) or PA (PY-IT and PY-DT) the difference of rDoC of actual lamellar\norder and expected lamellar order (ΔrDoC) shows higher value than that of SMA-based\nsystems (Figure 6a). The larger ΔrDoC indicates more quasi-aggregates existing in\nintermix region. As we defined, P-interface originates from these quasi-aggregates. The\ntrend of seven different blends indicates that PA systems exhibit more obvious P-\ninterface in intermix region.\nAdded discussion in main text Page 6:\nFigure 1a shows the chemical structures of polymer donors (PDs) D18 and PM6, small\nmolecular acceptors (SMAs) eC9 and Y6, and polymer acceptors (PAs) PY-IT and PY-\nDT. All of the D:A combinations have been widely used in high-efficiency SMA-based\nand all-polymer organic solar cells (OSCs).1 The energy levels for the representators,\nD18 (PD), eC9 (SMA), and PY-IT (PA) are determined by ultraviolet Photoemission\nSpectroscopy (UPS) and the intersection of the normalized absorption and\nphotoluminescence (PL) spectra (Figure 1b, 1c, S1 and S2)2.\nFigure 1. Chemical structures of photoactive materials and their physical properties.\nChemical structures of (a) PY-IT and PY-DT, (b) D18 and PM6, (c) eC9 and Y6. (d)\nEnergy levels of PY-IT, PY-DT, D18, PM6, eC9 and Y6, (e) Absorption of PY-IT, PY-\nDT, D18, PM6, eC9 and Y6.\nAdded discussion in main text Page 9:\n“The difference between the relative degree of crystalline (rDoC) of actual and\nexpected lamellar (ΔrDoC) of blends demonstrates the presence of lamellar order in\nintermix region, similar to previous observation (Figure 2c, S25 and S26).3 Therefore,\na key progress within transition is the formation of short-range aggregates of\namorphous acceptor (quasi-aggregates), which creates a special quasi-aggregated\nintermix region, containing the interfacial characteristics. The weaker miscibility of\nSMA with PD leads to weak percolation, constraining the growth of quasi-aggregates\nbut promoting the growth of pure region.4,5 In contrast, the stronger interfacial\npercolation in the PA system promotes larger quasi-aggregated intermix region and\nmore robust polymer network for charge transport (Figure 2c).6 The quasi-aggregates\nin intermix region can be uniformly observed across representative seven OPV systems\n(Figure S25-S27).”\nFigure 6b: ΔrDoC of four SMA systems and three PA systems.\nAdded information in SI:\nFigure S1. Normalized rDOC of actual and expected lamellar crossing four SMA\nsystems and three PA systems.\nFigure S18: The 2D GIWAXS pattern of neat and blends of PM6, Y6, PYDT, PM6:Y6,\nPM6:eC9, D18:Y6, D18:PYDT, PM6:PYDT.\nFigure S19: The 1D GIWAXS linecut in In-plane (IP) and Out-of-plane (OOP) of neat\nand blends of PM6, Y6, PYDT, PM6:Y6, PM6:eC9, D18:Y6, D18:PYDT, PM6:PYDT.\n2.“...... disordered phases exhibit higher energy levels and shallower HOMO depths\nthan ordered domains, also confirming by our UPS measurements” The authors suggest\nthat energy levels differ between ordered and disordered domains, supported by UPS.\nHowever, UPS typically probes the average occupied density of states at the film\nsurface. The levels of the individual materials tell nothing about the level alignment\nwhen they contact. UPS needs to be measured on the two materials in contact to claim\nthe HUMO level differences.\nResponse: We thank the reviewer for the insightful comments and suggestions. We fully\nagree that UPS for neat film cannot describe the energy level distribution in BHJ\nsystems, especially at the donor:acceptor interface. We believe that the UPS results for\npure materials partially describe the energy level properties of pure domain in BHJ\nsystem (Energy Environ. Sci., 2022, 15, 1545–1555; Energy Environ. Sci., 2023, 16,\n3416–3429). While at the interface, the energy level of donor and acceptor shift because\nof the interaction between donor and acceptor, such as electrostatic coupling and\nquadrupole moment, inducing vacuum level shifting and band bending (Nat\nCommun 2022, 13, 2046; Nat. Mater. 2021, 20, 378–3840). According to Baran et. al.\n(Energy Environ. Sci., 2025,18, 7610-7623), we tested the UPS for film processed with\ndonor amount of 10wt.% in solution which method results in a D:A ratio of close to 1:1\non the thin film making it more representative of the D:A ratio in real devices. In fact,\nsince the donor polymer becomes saturated on the film surface, the UPS measurements\nfor blends with ratios ranging from 10:1 to 10:15 may primarily probe the donor\npolymer, with only minimal contributions from intermixing and overlapping of the D18\nand PM6 frontier orbitals. We then focus on the energy landscape obtained from D:A\nof 1:10 UPS data. We utilize Gaussian functions and a Taugaard background to\ndeconvolute and estimate the HUMO of the donor-rich (HUMO ) and the acceptor-rich\nD\n(HUMO ) phase (Adv. Mater. 2022, 34, 2202575). Although such measurements are\nA\ninherently more challenging than those on pristine materials, determining the HUMO\nof blend films provides a more accurate picture of the energetic landscape in a\nrepresentative device. By de-convoluting the UPS spectra, the HUMO (5.1 eV for\nD\ndonor of PA system, and 5.15 eV for SMA system) can be observed to be slightly deeper\nthan that of pristine D18, while HUMO (5.39 eV for donor of PA system, and 5.35 eV\nA\nfor SMA system) is slightly shallower than its pristine film, indicating the presence of\na mixing phase (Figure S8). These observations agree with the existence of band\nbending and vacuum level shifting. Here we clarify the energy landscape of two systems\nfrom pure phase (represented by pristine films) to intermix phase (represented by D:A\nof 1:10 film) (Figure S9). It has been well proved that the pure phase is well packed\nleading to stronger crystallization and ordered structure, while the interface is more\ndisordered with higher HUMO level of acceptor and lower HUMO level of donor at\ninterface than pure materials (Energy Environ. Sci., 2022, 15, 1545–1555, J. Am. Chem.\nSoc. 2014, 136, 14078−14088). Our results agree with the finding that the HOMO level\nof the acceptor up-shifts and that of the donor down-shifts upon contact in a planar\nbilayer structure (Nat Commun 2022, 13, 2046). Besides, the ΔHUMO of pure and\nPA\ninterface is smaller than that of ΔHUMO may support the huge difference in\nSMA\nmorphological and energetic differences for SMA system with more disordered\ninterface.\nBesides, we further employed in-situ cyclic voltammetry coupled with UV-vis-NIR\nspectroscopy7,8 to investigate the highest occupied molecular orbital (HOMO) levels,\ncorresponding to ionization energies (IEs), in systems with varying donor-to-acceptor\n(D:A) ratios of 10:2, 10:5, and 10:10. These samples were prepared following the same\nprocedure as those used in solar cell characterization, with ITO as the substrate (Figures\nS9–S11). This combined approach has demonstrated its utility for tracking spectral\nchanges during electrochemical charging and for identifying oxidation onsets based on\nthe spectral transitions between neutral and first oxidized species. Our analysis centered\non the oxidation process of the blend films, which involved scanning the potential\ntoward positive values. From the oxidation behavior of both donor and acceptor\ncomponents, the HOMO levels and the HOMO difference (ΔHOMO) can be derived.\nFor reference, we also performed measurements on neat films of the individual\ncomponents, prepared identically to the blends, to aid in assigning characteristic\nabsorption features in the composite films.\nDuring a positive potential sweep, the neutral absorption bands of D180 at 570 nm\ndecreased, while a broad red-shifted band emerged near 900 nm, indicative of the\nradical cation D18⁺. A distinct isosbestic point was also observed at approximately 613\nnm. For the neat acceptor, the spectral changes involved a decrease in the main neutral\nabsorption peak (around 807 nm for PYIT0 and 840 nm for eC90), accompanied by the\nappearance of a blue-shifted band at 750 nm, attributed to the formation of the radical\ncations eC9⁺ and PYIT⁺. The spectral evolution during oxidation is displayed for all six\nblends (Figures S10–S11, left) over a potential range of 0.00 to ∼1.00 V vs. Fc/Fc⁺,\nwith the intensity changes of key absorption bands highlighted (Figures S10–S11, right).\nIn the case of D18:acceptor, as the potential increased from 0.00 V (black curve) to the\nmaximum (red curve), the absorption peak at 580 nm, characteristic of neutral D180,\nprogressively decreased. Concurrently, increased absorption at 690 nm and 900 nm\nsignaled the formation of D18⁺. An isosbestic point near 613 nm, consistent with the\nneat D18 film, was observed within this potential window.\nThese spectral trends were used to determine oxidation onsets via the tangent method.\nThe resulting potential values were converted to the Fermi scale using a correction\nfactor of –4.8 eV. Using the 580 nm band to identify the oxidation onset of D18,\nthe derived ionization energies were: for the PYIT system, IED-PA,10:2 = –5.10 eV,\nIED-PA,10:5 = –5.12 eV, and IED-PA,10:10 = –5.14 eV; for the eC9 system,\nIED-SMA,10:2 = –5.13 eV, IED-SMA,10:5 = –5.15 eV, and IED-SMA,10:10 = –5.15\neV. At higher potentials, a decrease in the 780 nm band reflected the oxidation of neutral\neC90 and PYIT0 to eC9⁺ and PYIT⁺. However, the acceptor oxidation was accompanied\nby a general absorption decrease across the 600–900 nm region, complicating the\nprecise determination of its onset. Therefore, the acceptor oxidation onset was\ndetermined based on the absorption at the D18 isosbestic point (~613 nm) in the blend,\nyielding: for PYIT systems, IEPA,10:2 = –5.40 eV, IEPA,10:5 = –5.38 eV, and\nIEPA,10:10 = –5.37 eV; for eC9 systems, IESMA,10:2 = –5.37 eV, IESMA,10:5 = –\n5.36 eV, and IESMA,10:10 = –5.35 eV (Figure S9c). Figures S9c and S9d summarize\nthe ionization energies for the six blends. The decrease in HOMOD18 with increasing\nD:A ratio aligns with a molecular packing reorientation from edge-on to face-on. The\nnearly constant HOMOD18 in eC9 blends at high D:A ratios suggests a rapid transition,\nwhereas the gradual decrease in PYIT blends indicates a more continuous change.8 The\ncalculated ΔHOMO values reveal a narrowing energy offset, suggesting a transition to\nan uphill energy landscape from pure domains to the D:A interface, consistent with\nearlier UPS deconvolution and analysis.\nAdded discussion in main text:\nWe perform the in-situ spectroelectrochemistry (SEC) measurement, the in-situ cyclic\nvoltammetry with UV-vis-NIR spectroscopy, to determine the energy level of interface\nunder different D:A ratio.31–33 By comparison, the disordered phase (interface) exhibits\nshallower HOMO depth than the pure acceptor (represented by pristine acceptor) and\nsmaller ΔHOMO difference (ΔHOMO) between donor and acceptor, indicating a uphill\nenergy landscape transition from pure domain to interface, also supporting by the\ndeconvolution of UPS spectra (Figure S7 – S11).6,34,35 Interestingly, the PA system\nshows continuously shallowed ΔHOMO, which might link to the morphology\nevolution.32\nAdded information in SI:\nFigure S2. The HUMO level of the blends of PA and SMA system with 10wt% polymer.\nFigure S3. Schematic of the energy level alignment at the donor–acceptor\nheterojunction for PA and SMA system.\nFigure S4. Absorption spectra recorded during cyclic voltammetry (insitu SEC) of the\nneat films of D18, eC9 and PY-IT in the neutral form (dark line) and the radical cation\nform (dash line). We also performedthe in-situ cyclic voltammetry with UV-vis-NIR\nspectroscopy, to analyse the HOMOs (IEs) of two systems with different D:A ratio, 10:2,\n10:5 and 10:10, with identical preparation as used for the solar cell characterization\nwith ITO as the substrate (Figure S9-S11). This technique has been proven to be useful\nin terms of mapping the spectral evolution during charging in electrochemical\nexperiments and determining the oxidation onsets from the spectral onset of neutral\nand first charged species. We focus on the oxidation of the blend films which involves\nthe potential scan to positive potentials. From the oxidation of donor and acceptor,\nthe HOMOs and HOMOs difference (ΔHOMOs) can be calculated. The oxidation of neat\nfilms of the single component (identical preparation as for blends) was done in parallel\nand is used to help identify characteristic absorption band in the blends. During a\npositive potential sweep, the neutral absorption bands of D180 at 570 nm and 620 nm\ndecrease and a broad bathochromically shifted band is appearing with its peak at 840\nnm, indicating the radical cation form D18+. One can also clearly identify a\ncharacteristic isosbestic point at ~ 615 nm. For neat acceptor, the spectral response\nduring cyclic voltammetry is a decrease of main peak (~807 nm for PYIT0 and ~840 for\neC90) band of the neutral molecule and the appearance of a new hypsochromically\nshifted band maximum at 750 nm, which is assigned to the formation of the radical\ncation form eC9+ and PYIT+.\nThe spectra of six blends (Figure S10-S11 left) during oxidation are shown in the\npotential range between 0.00 and ∼1.00 V vs. Fc/Fc+, and the intensity evolution of\ncharacteristic absorption bands is highlighted (Figure S10-S11 right). For L :Y5,\nPM6\nincreasing the potential from 0.00 V (black spectrum) to max voltage (red spectrum)\ngoes along with a decrease of the intensity of the absorption maximum at 580 nm which\nis characteristic for the continuous oxidation of the neutral D180. Parallel to this, the\nincrease of absorption at 690 and 900 nm indicates the formation of the radical\ncation D18+. Consistent with the spectra evolution of neat D18 an isosbestic point at\n~613 nm can be observed in this potential range. The peak evolutions can be used to\ndetermine the oxidation onsets via the tangent method. This method involves the\ntransfer of the potential onsets to the Fermi scale with a correction factor of −4.8 eV.\nHereby, the bands at 580 nm are used to determine the oxidation onset Eox of D18,\non\nwhich gives PYIT system, IE = −5.1 eV, IE = −5.12 eV, and IE = −5.14\nD-PA,10:2 D-PA,10:5 D-PA,10:10\neV; and eC9 system, IE = −5.13 eV, IE = −5.15 eV, and IE = −5.15\nD-SMA,10:2 D-SMA,10:5 D-SMA,10:10\neV. Increasing the potential continuously, the band at 780 nm is decreasing, showing\nthe oxidation of neutral eC90 and PYIT0 to the radical cation eC9+ and PYIT+.\nUnfortunately, the oxidation of acceptors go along with an overall decrease of the\nabsorption between 600 and 900 nm, which aggravates the determination of the\nexact oxidation onset from these spectra. We, therefore, base the determination of the\noxidation onset Eox (eC9 and PYIT) of acceptor on the absorption at the isosbestic\non\npoint of D18 in the blend at ~613 nm, which yields a value of PYIT systems IE = PA,10:2\n−5.4 eV, IE = −5.38 eV, and IE = −5.37 eV; and eC9 systems IE = −5.37\nPA,10:5 PA,10:10 SMA,10:2\neV, IE = −5.36 eV, and IE = −5.35 eV (Figure S9c). Figure S9c\nSMA,10:5 SMA,10:10\nand d plots the ionization energies of the six blends. The decreased HUMO by\nD18\nincreasing the D:A ratio agrees the packing orientation transition form edge-on to\nphase-on. The similar value of HUMO in eC9 blends at high D:A ratio indicates the\nD18\nrapid transition, while the continuously decreased HUMO in PYIT blends tells the\nD18\nconsistent transition. The calculated ΔHUMO shows a reduced ΔHOMO, indicating a\nuphill energy landscape transition from pure domain to interface, supporting the\nprevious UPS deconvolution and analysis.\nFigure S5. Absorption spectra (left) for selected potentials recorded during oxidation,\nand the corresponding peak trends (right) for D18:eC9 with 10:2, 10:5, and 10:10\nD:A ratio (top to down).\nFigure S6. Absorption spectra (left) for selected potentials recorded during oxidation,\nand the corresponding peak trends (right) for D18:PYIT with 10:2, 10:5, and 10:10\nD:A ratio (top to down).\n3. For the electron-phonon interaction, this is a crucial physical process in organic\nmaterials, crucial for charge recombination. The authors should provide a systematic\ndiscussion of this aspect.\nResponse: We thank the reviewer for the insightful comments and suggestions. We\nadded a Note for electron-phonon interaction.\nAdded Notes 3 in S1:\nThe electron-phonon interaction is a fundamental process governing the electronic and\noptical properties of organic photovoltaics. Due to localized electronic states and a soft,\nvan der Waals-bonded lattice, this coupling is particularly strong, leading to the\nformation of polarons and a significant reorganization of the nuclear framework upon\ncharge transfer or excitation. This is quantitatively embodied by a large Huang-Rhys\nfactor (S), which manifests experimentally in broad, vibronically-structured emission\nspectra. Crucially for charge recombination, this interaction provides a dominant\npathway for non-radiative decay. The energy released during charge recombination is\nefficiently dissipated as heat through vibrational modes: the process of energy\ndissipation as heat during charge recombination is fundamentally governed by\nelectron-phonon coupling. It begins when an excited electron distorts the surrounding\natomic lattice, creating a system in a non-equilibrium configuration. During the\ninstantaneous, Franck-Condon transition of recombination, the electron drops to the\nground electronic state, but the heavy, slow-moving nuclei remain in their distorted\npositions. This places the entire system high up on the ground state's vibrational\npotential energy surface. The system then rapidly relaxes to its true minimum energy\nconfiguration by transferring this excess energy into the lattice. This relaxation occurs\nthrough the generation of a large number of high-energy vibrational phonons. These\nphonons subsequently scatter and decay into a broader distribution of lower-energy\nphonons through phonon-phonon interactions, effectively randomizing the energy and\ndissipating it as heat throughout the material. This process is governed by the energy\ngap law that severely limits the luminescence efficiency of low-gap systems and\ncontributes to voltage losses in photovoltaic devices. Therefore, a systematic\nconsideration of electron-phonon coupling is indispensable for interpreting charge\nrecombination dynamics, whether in exciton decay, charge-transfer state behavior, or\ncharge recombination, and is key to advancing the performance of organic light-\nemitting diodes and solar cells.\nThe role and mathematical description of electron-phonon coupling in organic\nphotovoltaics are fundamentally different from those in traditional inorganic crystals\n(like the superconductors). The core concept is localization and the formation of\npolarons.\nThe key quantum mechanical expressions used to describe this are based on the\nHolstein model, which perfectly captures the physics of localized electrons interacting\nwith molecular vibrations.\nThe Hamiltonian for an electron in an organic material is typically divided into three\nparts:\n   =    +   +  \n         \nWhere    is the electron energy,    is the phonon (molecular vibration) energy,\n    \nand    is the electron-phonon interaction.\n    \nIn organic materials, electrons are not delocalized in bands but are localized on\nindividual molecules or polymer segments. They \"hop\" from one site to another. This is\ndescribed by a tight-binding model:\n   =     ̂    ̂ −     ( ̂    ̂ + ̂    ̂ )\n                  \n  〈  〉\nWhere  ̂   and  ̂ are the creation and annihilation operators for an electron (or hole)\n   \non molecular site  ;   is the on-site energy, this is the energy of an electron residing\n \non a specific molecule. At a donor-acceptor interface, the   for donor and acceptor\n \nmolecules are different, creating the driving force for charge separation;   is the\n  \ntransfer integral (or electronic coupling). It quantifies the ease with which an electron\ncan hop between neighboring molecules   and   , this is a critical parameter for\ncharge carrier mobility.\nThis    term describes the energy of an electron \"hopping\" between localized\n  \nmolecular orbitals.\n1\n   =  ℏ  (      + )\n         2\n \n     and    are the creation and annihilation operators for a quantized molecular\n   \nvibration (a phonon) on molecular site  ; ℏ  is the energy of that specific molecular\n \nvibration.\nIn organic materials, the coupling is predominantly local, meaning an electron only\ninteracts with the vibrations of the molecule it currently occupies. This is described by\nthe Holstein coupling:\n   =    ℏ   ̂    ̂ (     +   )\n                \n \n  is the dimensionless local electron-phonon coupling constant. It is the central\n \nparameter of the model which quantifies how much the molecular geometry of\nsite   relaxes when an electron occupies it.\n ̂    ̂ is the electron number operator    which means the coupling is only \"active\"\n     \non the specific molecule that the electron occupies. It equals 1 if the site   is occupied\nby an electron, and 0 otherwise. (   +   ) operator is proportional to the\n   \ndisplacement operator    of the molecular vibration. Therefore, this coupling term\n \nrepresents the fact that the energy of the electron depends on the nuclear coordinates\nof the molecule.\nThe process described by this Hamiltonian is that when an electron hops onto a\nmolecule ( ̂    ̂ = 1), it exerts a force on the atoms via    . This force distorts the\n        \nmolecule's equilibrium geometry (e.g., lengthening a bond). The electron and the lattice\ndistortion it creates become trapped together, forming a new quasiparticle called a\npolaron. The polaron has a larger effective mass, which reduces charge carrier mobility.\nThese quantum expressions directly lead to critical phenomena in organic solar cells,\nat the donor-acceptor interface, the photogenerated exciton (electron-hole pair) must\nseparate against its Coulomb attraction. The lattice relaxation, quantified by the inner\nreorganization energy   =   ℏ , stabilizes the separated charge pair. It lowers the\nenergy of the charge-separated state, providing an extra driving force. Strong coupling\ncreates a distinct CT state at the interface, whose energy and lifetime are deeply\ninfluenced by the coupling strength  .\nCharge transport occurs via polaron hopping between molecules. The non-radiative\nrecombination decay rate is described by Marcus Theory. The rate   is:\n  \n|  |  (    + ) \n  \n  ∝     −  \n            4      \nHere,   =   ℏ  is the reorganization energy. Strong coupling (large  ) slows down\nthe hopping rate, reducing charge carrier mobility. When electrons and holes (polarons)\nrecombine, the electron-phonon coupling provides a pathway for energy dissipation.\nThe electronic energy is converted into heat (many vibrational quanta) via the   \n    \nterm. The non-radiative recombination rate   also depends critically on  . In many\n  \ncases, a larger   leads to faster voltage loss. Therefore, mastering the control of\nelectron-phonon coupling is essential for designing high-performance organic solar\ncells with low energy loss.\n4.The decomposition of GIWAXS in-plane scattering into donor, acceptor, and quasi-\naggregated contributions is insightful. However, the physical basis for introducing a\nquasi-aggregate component—distinct from donor/acceptor neat contributions—should\nbe better justified. How to understand the quasi-aggregate component? Will these\naggregated free molecules arise the electron trap due to the large LUMO offset between\ndonor and acceptor? What is the difference between the polymer acceptor and small\nmolecular acceptor?\nResponse: We thank the reviewer for the insightful comments and suggestions. The\nquasi-aggregate component identified in the GIWAXS analysis represents a critical\nmorphological state that is structurally and electronically distinct from both the pure\ndonor/acceptor domains and the fully amorphous mixed region. Physically, these quasi-\naggregates are nascent, interconnected aggregates of acceptor molecules within the\nintermixed matrix. They possess a degree of molecular order and π-π stacking, as\nevidenced by their distinct scattering signature, but lack the long-range crystallinity and\ncoherence of pure phases (detailed can be found in modified Note S2). Our justification\nstems from the existence of crystalline property in intermix regions which conflict with\nprevious understanding. In BHJ blends, there are three morphological structures at\nintermix region, isolated acceptor clusters, quasi-aggregates, and entangled donor-\nacceptor intermix. We connect the performance losses and charge generation observed\nin these blends with morphological difference, particularly for PA which are prone to\npenetration into donor matrix.\nFigure R1. Schematics showing three different morphological structures in intermix\nregion of BHJ blends for SMA based systems and pure phase of donor and acceptor\n(Nat Commun 2024. 15, 2784).\nRegarding electron traps, the formation of quasi-aggregates might be the mechanism to\nsuppress them. Isolated acceptor clusters might act as deep electron traps because of\nthe large LUMO offset between the isolated cluster and the surrounding donor-rich\nenvironment (Energy Environ. Sci., 2024, 17, 8893–8903). An electron localized in\nsuch a small cluster faces a significant energy barrier to escape. We argue that the quasi-\naggregate, by connecting these isolated clusters into a larger, more ordered structure,\nmight fundamentally alter the electronic landscape. The more pronounced existence of\nquasi-aggregates is found to effectively suppress deep traps (Energy Environ. Sci., 2024,\n17, 8893–8903). The increased size and improved molecular ordering of the quasi-\naggregate lead to a shallower LUMO level (higher-lying energetically) compared to an\nisolated cluster. This reduces the effective energy offset for electron escape, thereby\ndiminishing the trap depth and facilitating charge transport rather than trapping.\nCertainly, this new observation has been demonstrated to aid in understanding the\nperformance deviations within SMA systems but has not been proved to be effective in\nPA systems. By s-EQE, the PY-IT based OPV devices shows fewer deep traps than\nBTP-eC9 based devices, which also agree with our results and inspire us (Joule 2024\n8(2), 509-526). Although we already observed a more pronounced existence of quasi-\naggregates and a more efficient charge generation kinetics in PA systems, in the future,\nmore detailed studies focusing on how those quasi-aggregates induced P-interface\neffects deep traps will be performed.\nAdded discussion in main text P9:\n“The difference between the relative degree of crystalline (rDoC) of actual and\nexpected lamellar (ΔrDoC) of blends demonstrates the presence of lamellar order in\nintermix region, similar to previous observation (Figure 2c, S25 and S26).11 Therefore,\na key progress within transition is the formation of short-range aggregates of\namorphous acceptor (quasi-aggregates), which creates a special quasi-aggregated\nintermix region, containing the interfacial characteristics. The weaker miscibility of\nSMA with PD leads to weak percolation, constraining the growth of quasi-aggregates\nbut promoting the growth of pure region.24,40 In contrast, the stronger interfacial\npercolation in the PA system promotes larger quasi-aggregated intermix region and\nmore robust polymer network for charge transport (Figure 2c).41 The quasi-aggregates\nin intermix region can be uniformly observed across representative seven OPV systems\n(Figure S25-S27).”\n“We propose to utilize ΔrDoC to qualitatively determine the population of P-interface.\nAs a results, PA system presents a more substantial P-interface population (larger\nΔrDoC). In sharp contrast, the rapid transition of SMA system indicates the limited\ndevelopment of both E- and P-interface (small ΔrDoC), with the dominated former. We\nspect that the formation of isolated acceptor units (or tiny clusters) in isotropic\nintermix region may lead to the deep traps at E-interface, while the formation of short-\nrange quasi-aggregates at P-interface may supress those deep traps, which promote the\nenergetic order.42,43”\nAdded information in SI Note S2:\n“We selected peaks which were isolated from other peaks and only existed in donor or\nacceptor itself to quantify the contribution of pure phase staking in total blend film.\nMore specifically, the rDoC of the selected peaks represents the volume fraction\ncontribution from the pure crystalline-donor and pure crystalline-acceptor regions.\nWhile we also extracted the rDoC of lamellar stacking peak from blend which\nrepresents the total crystalline information from both pure donor, pure acceptor, and\nalso intermix region. By normalization, we can analysis the contribution of intermix\nregion in total lamellar stacking from calculating the difference, that is ΔrDoC,\nbetween total lamellar stacking rDoC (actual lamellar order) and the sum rDoC of\npure donor and pure acceptor (expected lamellar order). This difference, ΔrDoC,\ndescribe the extent of aggregates existing in intermix region.”\n5. The manuscript introduces two distinct types of donor-acceptor interfaces, the\nEntangled-interface (E-interface) and Penetrated-interface (P-interface), based on\nmorphological features at different D:A ratios. While this is a valuable conceptual\nframework, the criteria for assigning these identities could benefit from further\nclarification. Specifically, what is the quantitative threshold for defining the interface\nof organic solar cell systems as E- or P-type, or even the parameter to help people\nquantify the categories and concentration of interface? Is it based on a certain level of\ncrystalline, FWHM values, or intermix factor (Λ)? Including a more systematic or\ncontinuous metric (e.g., an interface order index) would increase the robustness and\ngeneralizability of this classification scheme.\nResponse: We thank the reviewer for the insightful comments and suggestions. We fully\nagree that we need to provide a parameter to quantify the degree of E- and P-interface.\nHere we propose two parameters to describe two interfaces, ΔrDoC and A /A (the\n1 2\nweight coefficients of from charge ttransfer kinetics). As we claimed, P-interface is\nstrongly related to quasi-aggregates, which means the population of quasi-aggregates\nmay describe the degree of P-interface. Therefore, we propose to utilize ΔrDoC to\nquantify the population of P-interface. The value of A /A quantifies the ratio of E-\n1 2\ninterface and P-interface, which can be utilized to calculate the relative population\nbetween two interfaces. The value of ΔrDoC is normalized, which means it can be\ncompared directly. This value proves the existence of P-interface and describes the\npopulation of P-interface. While the value of A /A gives the direct relation of the\n1 2\npopulation of P-interface and E-interface. Therefore, it is possible for people to clarify\nthe whole picture for the population of two distinct types of donor-acceptor interfaces.\nAdded discussion in main text P9:\n“We propose to utilize ΔrDoC to qualitatively determine the population of P-interface.\nAs a results, PA system presents a more substantial P-interface population (larger\nΔrDoC). In sharp contrast, the rapid transition of SMA system indicates the limited\ndevelopment of both E- and P-interface (small ΔrDoC), with the dominated former. We\nspect that the formation of isolated acceptor units (or tiny clusters) in isotropic\nintermix region may lead to the deep traps at E-interface, while the formation of short-\nrange quasi-aggregates at P-interface may supress those deep traps, which promote the\nenergetic order.42,43”\nAdded discussion in main text P16:\n“The evolution of the E-interface (  ) and P-interface (  ) charge transfer weight\n   \ncoefficient, quantifying the ratio of two interfaces, aligns with the growth trends of the\nP-interface in two systems (Figure 4b).”\nAdded discussion in main text P22:\n“We attribute the formation of P-interface to the growth of quasi-aggregates existed in\nintermix region, quantifying by the value of ΔrDoC (Figure 6b). ...... The calculated\ncharge transfer rate coefficient ratio of P- and E-interface (  /  ) provides the\n   \nstraightforward relation of the population of two interface.”\nAdded discussion in main text P24:\n“We propose that the relative population of E- and P-interface can be estimated by\ncalculating ΔrDoC and   /  .”\n   \n6.“This observation indicates that the P-interface possesses more pronounced edge-on\nfeatures than either the amorphous E-interface or the pure domains (dominated by face-\non orientation).” The authors state that the transition from edge-on to face-on packing\nis convincingly demonstrated using FWHM, Az/Axy, and Herman’s parameter.\nHowever, the recent discussion is all focus on morphology without the implications of\nthese orientation shifts on electronic processes, particularly charge transport across\nor along the interface, are not fully articulated. It would be better to test the charge\ntransport mobility, especially the transport at in-plane direction, to confirm the\ntransition.\nResponse: We thank the reviewer for the insightful comments and suggestions. We then\ntest the mobility of SMA and PA systems working in OPV and Organic Field Effect\nTransistor (OFET) to monitor the charge transport mobility at out-of-plane (OOP)\ndirection and in-plane (IP) direction. The PA system shows faster   and   in both\n   \nIP and OOP transport direction, agreeing with literature (Nat Commun 2025, 16, 654).\nFrom electron only devices, we found that the IP direction electron mobility (  ) of PA\n \nsystem increases faster than SMA systems. This might indicate that the PA system\nexhibits more edge-on packed components. We argued that this might also support that\nthe P-interface dominated PA devices possessed more edge-on features than SMA\ndevices as seen in Figure 2d. Besides, we also observe the gradual decrease in hole\nmobility (  ) of OFET devices and increase in OPV devices, which indicates the phase\n \ntransition from edge-on dominant to phase-on dominant. The superior mobility property\nof PA system might originate from the better connectivity of polymer units forming a\nmore robust network (Nat Commun 2025, 16, 654).\nAdded discussion in main text on page 8:\n“…This phase transition can also be observed from charge transport mobility evolution\nboth in In-plane (IP) and out-of-plane (OOP) direction measured from OFET and OPV\ndevices (Figure S24).”\nAdded discussion in main text on page 9:\n“… In contrast, the stronger interfacial percolation in the PA system promotes larger\nquasi-aggregated intermix region and more robust polymer network for charge\ntransport (Figure 2c).41”\nAdded discussion in main text on page 10:\n“… The comparatively more apparent edge-on characteristics are observed in the PA\nsystem, cautiously supporting by higher electron mobility and its faster evolution in\nOFET devices (Figure 2d, S24).”\nAdded information in SI:\nOFET fabrication and measurement.\nSubstrates with source and drain contacts (Ti/Au, 2/35 nm) were custom-made in First\nMEMS Co., Ltd. using photolithography process. Before organic semiconductor\ndeposition, the substrates were cleaned by sonication in deionized water, acetone and\nisopropanol for 5 minutes each, and were then dried in an oven under ambient\natmosphere at 120 oC for 10 minutes, treated with UV-O for 15 minutes, and then\n3\npassivated by using decyltrichlorosilane (from Gelest Chemicals) from a 1 vol%\nsolution in toluene at 120 oC for 2 hours. The substrates were then rinsed and sonicated\nin toluene and dried under nitrogen flow. Organic semiconductor films were spin-\ncoated from their solutions in chloroform. The concentration of all solutions is 5 mg/mL.\nThe final device architecture (from bottom to top) for these bottom gate, bottom contact\nfield-effect transistors was Si/SiO /DTS/Ti/Au/organic semiconductor layer. The\n2\nmobility of OFET devices were obtained by fitting the following equation to the\nsaturation regime transfer characteristics: I = (W/2L) C μ (V – V)2, where W is the\nd i g t\nchannel width (1000 μm), L is the channel length (80 μm), C is the gate dielectric layer\ni\ncapacitance per unit area (11 nF/cm2), V is the gate voltage, V is the threshold voltage,\ng t\nand I is the source-drain current. Devices were measured under nitrogen in a glovebox.\nd\nFigure S74. Measured electron (  ) and hole (  ) mobility in IP and OOP direction\n   \nfrom OFET and OPV devices, respectively.\n7.The author fitted CT state properties by only EL spectra, differing from the common\npractice of co-fitting sEQE and EL. What is the justification for using only EL?\nHow does this approach compare in accuracy or applicability to co-fitting methods?\nResponse: We thank the reviewer for this insightful question regarding our\nmethodology for characterizing the charge-transfer (CT) state. Our decision to rely\nprimarily on electroluminescence (EL) spectroscopy, rather than the common practice\nof co-fitting sensitive external quantum efficiency (sEQE) and EL spectra, was\nnecessitated by the distinct photophysical properties of low-bandgap non-fullerene\nacceptor (NFA) blends, which make the sEQE measurement of the CT absorption\nimpractical or uninformative. The justification is twofold, rooted in the spectral\ncharacteristics and interfacial energetics of these systems.\nFigure R2. EQE (sEQE) spectrums for PCBM fullerene (FA)-based and Y6 (NFA)-\nPV\nbased photovoltaic device measured at room temperature. The small black triangles\nindicate the band edge of pristine D18 and PC71BM. The grey area under the\nD18:PC71BM curve (solid red line) illustrates the additional CT-absorption observed\nin fullerene-based devices (Mater. Adv., 2021,2, 4291-4302).\nFirstly, for the majority of the donor:NFA blends studied here, the CT absorption\nsignature is spectrally obscured and cannot be reliably detected via sEQE measurements\n(Figure S9) (Nat. Mater. 2021 20, 378–384, Mater. Adv., 2021,2, 4291-4302). This is in\nstark contrast to fullerene-based systems like D18:PC₇₁BM, where the low oscillator\nstrength of the fullerene at the low-energy edge of its absorption and the significant\nenergy separation between the CT state and the acceptor's Frenkel exciton absorption\nallow for a clear distinction of the CT absorption band (Figure R1) (Phys. Rev. B 2010,\n81, 125204). In NFA blends, the CT state energy (E ) is typically higher and closer to\nCT\nthe optical gap of the acceptor. Consequently, the weak CT absorption band is entirely\nmasked by the exponentially decaying tail of the much stronger absorption of the NFA\nsinglet state, rendering it invisible in sEQE spectra.\nFigure R3. Reduced sEQE and EL spectrum for D18:PCBM and D18:Y6 photovoltaic\ndevices measured at room temperature. The gray curves are fits of the sEQE and EL\nspectra with the same values for E and λ (Mater. Adv., 2021,2, 4291-4302).\nCT\nSecondly, because the CT absorption is inaccessible, EL remains the only viable\nexperimental observation for probing the CT state. However, the EL spectrum of a\ndonor:NFA blend is typically a composite signal, leading to a strong superposition\nbetween the emission of the acceptor singlet states and CT states. To deconvolute this\ncomposite spectrum and extract the CT state parameters, we fitted the blend reduced\nEL spectrum (    ) as a linear combination of the singlet emission and a Gaussian-\n     \nshaped function band representing the CT state emission according to Marcus Theory\nand Eq. R1:\n  −      (∆  −  − ) \n    =     exp      +       −        ( 1)\n           4        4       \nWhere the first term is the Gaussion-shaped singlet emission,   and   is the pre-\n   \nexponential factors,   is the singlet energy which can also be determined from\n \npristine EL spectra.   is the standard deviation (width) of fitted Gaussian. The other\n \ninformation can be found in Notes S3. Certainly, our fitting does not capture the true\ncenter of the full CT density of states. A more precise evaluation would require\nsophisticated optical simulations to correct the EL spectra for the device's outcoupling\nefficiency, which was beyond the scope of this comparative study (Nat Commun 2018\n9, 3631).\n8.“In the SMA system, the CTEs population is larger than those in SMA system”\nappears to be a typo and creates confusion.\nResponse: We thank the reviewer for this insightful comment and correction. We\ncorrected the sentences and re-checked the paper to correct all typo questions.\nCorrected information in main text P14:\n“The CTEs population in the SMA system is larger than those in PA system.”\n9. The conclusion that EPC is stronger at interfaces of SMA system than PA system is\ndrawn from the D18:PYIT and D18:eC9 systems. Would this trend hold for other donor-\nacceptor pairs, or is it specific to these materials?\nResponse: We thank the reviewer for the insightful comments and suggestions. We\nagree with the reviewer that the universality of EPC trend in two systems is critical for\nthe communities. To prove the universality that PA systems possess relatively lower\nEPC than SMA systems, we introduce another three materials, PM6 (PD), Y6 (SMA),\nand PY-DT (PA). Here, PM6 is another well utilized polymer donor in OPV. We select\nPM6 to show if the trend in main text is caused by D18. Y6 and PY-DT are also very\npopular SMA and PA. We measured the absorption and PL spectra for D18:Y6, D18:PY-\nDT, PM6:Y6, PM6:PY-DT. Combined with two combinations discussed in main text,\nD18:eC9, D18:PY-IT, we totally obtained 7 difference D:A combination. We calculated\nthe S value according to the method in Note S5. The results show the consistent trends\nthat PA systems show lower S value than that of SMA systems. Here, we amend the\nconclusion to that the Y6-based SMA systems exhibit larger EPC than that of Y6\nderived PA systems.\nAdded discussion in main text on page 17:\n“…We further calculate the S value for seven systems (Figure S40), including four SMA\nsystems and three PA systems, where SMA systems always exhibit higher value than PA\nsystems, thereby ensuring the validation across the state-of-the-art OPV systems.”\nFigure 6a. Mechanism diagram and universality of more pronounced P-interface\nwith weaker EPC reducing non-radiative voltage loss in OPVs. The calculated S\nfactor value of SMA, PA and ternary systems,\n10.For recent small energy offset systems, please discuss the contribution to ΔVnr from\nother parameters such as reorganization energy and electronic couplings under the\neffects of reduced EPC. Can the relative contributions of these factors be estimated or\ndecoupled?\nResponse: We thank the reviewer for the insightful comments and suggestions. We are\nvery agreed that the effects from parameters expect EPC need to be further analyzed\nand discussed to understand the contribution of each value. We then utilized the\nparameter shown in Table S5 for further analyzing the effects of outer reorganization\nenergy (  ) transition dipole moment       ⃗ . Here we can calculate the electronic\n  i-f\ncoupling (  ) from transition dipole moment according to Eq. S16. Here we utilize  \ni-f i-f\nfor further analysis. Nelson et. al., already discussed how the parameters from MLJ\nequation and spontaneous emission effect V according to two state model where the\nOC\nreducing of inner reorganization energy (  ) and ΔE contribute most on V\n  S1-CT OC\nincreasing (PHYS. REV. X 2018, 8, 031055). However, this only introduces two state\nmodel but three state model which considers the hybridization between S state and CT\n1\nstate. We firstly set S = 1 and change the value of outer reorganization energy (  ),\no\nelectronic coupling between S and CT state (t ); electronic coupling between S\nand S state (t ); and electronic coupling between CT and S state (t ). From Fig\nS55 and Table S6-S7, it is obvious that the effect of   is independent on the change of\no\nΔE with an 85 meV V increase by reducing   from 0.2 eV to 0.1 eV. While the\nS1-CT OC o\nelectronic couplings are strongly related to ΔE . The small ΔE (also known as\nS1-CT S1-CT\nsmall energy offset situation) may supress the effects from electronic couplings, in\nwhich situation the increasing of FCWD(0) and FCWD(E ) may dominant the k\nCT-S0 nr\nand k . When we set the ΔE to be 100 meV, the increase of t from 10 meV to\nr S1-CT S1-CT\n100 meV gives rise to a 77 meV V increase, while the reduction of t and t\nOC S1-S0 CT-S0\nfrom 300 meV to 20 meV exhibit 30 meV and 90 meV V increase, respectively. When\nOC\nwe reset the ΔE to 50 meV, the same variations induce 61 meV, 43 meV and 62\nS1-CT\nmeV V increase, respectively. Therefore, the reduction of t and increase of t\nOC CT-S0 S1-CT\nalmost contributes the same on increasing V , while the reduction of t shows\nOC S1-S0\nsmallest effect on increasing V . We proposed that, by considering the hybridization\nOC\nof CT state and singlet state S , the strategy for increasing V is extensive where the\n  is relatively promising since its independence with the change of ΔE . Besides,\no S1-CT\nt and t also need to be controlled, keeping as higher t as possible according\nS1-CT CT-S0 S1-CT\nto the intensity borrowing mechanism (Nature Mater 2018, 17, 703–709) and smaller\nt . This is because although the larger t brings the faster   , the  \nCT-S0 CT-S0  ,        ,     \nalso increase and even compensating the increase of   leading to larger qΔV .\n ,      nr\nWe then turn to analyse the V increase by resetting the S value to 0.8. We mainly\nOC\ncompared the qΔV reduction by changing the EPC and four parameters mentioned\nnr\nabove,   , t , t , and t , shown in Fig S56 and Table S8-S9. The increase in\no S1-CT S1-S0 CT-S0\nV caused by the reducing of   is unrelated to the reduction of EPC, maintaining the\nOC o\nV increase of ~85 meV when reducing   from 0.2 eV to 0.1 eV. Besides, we found\nOC o\nthat by reducing S, the effects of all four parameters on V increase are slightly\nOC\nsupressed. This trend is more obvious when ΔE reduces from 100 meV to 50 meV.\nS1-CT\nFor instance, by setting ΔE to 100 meV, the reduction of EPC is almost independent\nS1-CT\nwith four parameters, where the increase of t from 10 meV to 40 meV shows a 3\nS1-CT\nmeV suppression in V increase. While when ΔE is 50 meV, increasing t\nOC S1-CT S1-CT\nshows a 12 meV suppression in V increase. However, these suppressions are not\nOC\nsufficient to compensate the V increase achieved from EPC reduction, which is about\nOC\n45 meV (Figure 5c). In very small energy offset systems, the V increase by change\nOC\nelectronic coupling may reach the threshold (Nat Energy 2021, 6, 799–806). The EPC\nreduction is able to slightly reduce the threshold for lower qΔV . Thus, we conclude\nnr\nthat it is possible but complex to decouple the effects from parameters except EPC,\nespecially in real devices case. However, by simulation, we can predict the\ncontributions that the other parameters are almost independent with EPC since in real\ncase, those parameters might not change as much as in simulation.\nAdded discussion in main text on page 19:\n“Beyond EPC, prior studies have identified that parameters such as, ∆  ,   ,\n  -     \n  , and   , also contribute to the reduction of qΔV .49,62 It is therefore crucial to\n  -     nr\ndistinguish the individual contribution of each parameter to qΔV . Regardless of the\nnr\nEPC, the reduction in qΔV achieved by lowering   is independent of the change of\nnr  \n∆  , whereas V increases by varying the   ,   , and   are as the\n  -   OC   -     -        \nfunctions of ∆  (Figure S61 and Table S10-11). Specifically, the V increase by\n  -   OC\nreducing   , from 200 meV to 100 meV, remains consistent, as ~ 85 meV. Conversely,\n \nthe positive impact of modulating electronic couplings (or transition dipole moment)\non V is gradually diminishes as ∆  decreases. However, this diminishing effect\nOC   -  \ncould be counteracted by reducing EPC which is isolated from ∆  (Figure S62\n  -  \nand Table S12-13). Such a reduction of EPC might further enhance the molecular\nPLQY and EQE ,63 and is also independent of ∆  , presenting a potential strategy\nEL   -  \nfor supressing non-radiative energy loss of OSCs.\nThe non-radiative energy losses in the two systems were analysed following the insights\nfrom numerical simulations. Calculation of the recombination rates,   ,\n ,     \n  , and qΔV as functions of EPC based on the experimental parameters (Table\n  ,      nr\nS7) show a consistent ~28 meV lower qΔV for P-interface dominant devices\nnr\n(D:A=10:15) compared to E-interface dominant ones (D:A=10:1) across both PA and\nSMA systems (Figures 5d, 5e, S63). Attribution of this reduction points to the smaller\nreorganization energy and stronger hybridization effects of P-interface. Decomposition\nof the contributions confirm   as the dominant factor, consistent with simulations\n \n(Figure S64). It is notable that the reducing of ∆  might enhance both the\n  -  \nelectronic part of   and   , making careful balancing of them essential. Similarly,\n    \nreplacing SMA with PA reduces qΔV by ~25 meV also due to the smaller ∆ \nnr   -  \nand larger   leading to enhanced S -CT state hybridization, and smaller   .”\n  -   1  \nFigure S61.The change of non-radiative energy loss qΔV by reducing λ , t , t ,\nnr 0 S1-CT S1-S0\nand t\nCT-S0.\nFigure S62.The change of non-radiative energy loss qΔV by reducing λ , t , t ,\nnr 0 S1-CT S1-S0\nand t with two potential S value of S = 1 and S = 0.8\nCT-S0 .\nAt low EPC, the achievable suppression of ΔV from other parameters is weaken, with\nnr\nthe exception of   , which maintains a consistent ~85 meV V increase (Table S12-\n  OC\n13). For instance, the increase of   contributes 53 meV and 56 meV V increase\n  -   OC\nat S = 0.8 and 1, respectively, under a relatively large energy offset (∆  = 100\n  -  \nmeV). However, this contribution is supressed to 33 meV and 45 meV in low energy\noffset (∆  = 50 meV). This weakened contribution is predictable since the fixed\n  -  \nk and k (or PLQY in a macroscopic description) of low-optical-gap material in\nnr,S1 r,S1\nsimulationdrawing the achievable threshold. More importantly, although the achieved\nV increase from electronic coupling (or transition dipole moment) are weaken, we\nOC\nreduced EPC “down-shift” the non-radiative energy loss by reducing ∆  .\n  -  \nThis down shift almost isolate to hybridization, which will not be affected by ∆  and\n  -  \nReduced EPC provide a potential change to reduce q∆  directly.\n  \nTable S10. Potential V increasing when changing different parameters when S = 1\nOC\nand ΔE = 100 meV.\nS1-CT\nParameter improvement strategy V increase\nOC\nReduce the outer reorganization energy (  ) from 0.2 to 0.1 eV 85 meV\no\nIncrease the electronic coupling between S and CT state (t\n) 77 meV\nCT\nfrom 0.01 eV to 0.1 eV\nReduce the electronic coupling between S and S state (t )\n1 0 S1-S0\n30 meV\nfrom 0.3 eV to 0.025 eV\nReduce the electronic coupling between CT and S state (t )\n90 meV\nfrom 0.3 eV to 0.025 eV\nTable S11. Potential V increasing when changing different parameters when S = 1\nOC\nand ΔE = 50 meV.\nS1-CT\nParameter improvement strategy V increase\nOC\nReduce the outer reorganization energy (  ) from 0.2 to 0.1 eV 83 meV\no\nIncrease the electronic coupling between S and CT state (t\n) 61 meV\nCT\nfrom 0.01 eV to 0.1 eV\nReduce the electronic coupling between S and S state (t )\n1 0 S1-S0\n43 meV\nfrom 0.3 eV to 0.025 eV\nReduce the electronic coupling between CT and S state (t )\n62 meV\nfrom 0.3 eV to 0.025 eV\nTable S12. Potential V increasing when changing different parameters when S = 0.8\nOC\nor S = 1.0 and ΔE = 50 meV.\nS1-CT\nParameter improvement strategy V increase\nOC\n(meV)\nΔE = 50 meV S =0.8 S = 1.0\nS1-CT\nReduce the outer reorganization energy (  ) from 0.2 to 0.1 76\no\n83\neV\nIncrease the electronic coupling between S and CT state (t\n) 33 45\nCT\nfrom 0.01 eV to 0.1 eV\nReduce the electronic coupling between S and S state (t )\n1 0 S1-S0\n5 10\nfrom 0.3 eV to 0.025 eV\nReduce the electronic coupling between CT and S state (t\n) 8 18\nS0\nfrom 0.3 eV to 0.025 eV\nTable S13. Potential V increasing when changing different parameters when S = 0.8\nOC\nor S = 1.0 and ΔE = 100 meV.\nS1-CT\nParameter improvement strategy V increase\nOC\n(meV)\nΔE = 100 meV S =0.8 S = 1.0\nS1-CT\nReduce the outer reorganization energy (  ) from 0.2 to 0.1 84\no\n85\neV\nIncrease the electronic coupling between S and CT state (t\n53 56\n)\nCT\nfrom 10 meV to 40 meV\nReduce the electronic coupling between S and S state (t )\n1 0 S1-S0\n6 7\nfrom 75 meV to 25 meV\nReduce the electronic coupling between CT and S state (t\n) 25 32\nS0\nfrom 75 meV to 25 meV\n11.The discussion emphasizes that introducing a ternary component promotes P-\ninterfaces, yet provides no metric or descriptor for how this structural change is\nquantified or inferred.\nResponse: We thank the reviewer for the insightful comments and suggestions. We fully\nagree that we need to prove the availability of our proposed ternary strategy. We\ntherefore calculated the ΔrDoC and S factor. We found that ΔrDoC shows increase\nvalue and S factor shows the reduced value. This can be attributed to the cooperation\nof PY-IT. Here we only incorporate small amounts of PY-IT, 0.2, to keep high J and\nSC\nFF achieved from D18:eC9 binary system. Therefore, we conclude that the\nincorporation of PY-IT into SMA system increases the population of P-interface and\nreduces the electron-phonon coupling of systems. All this leads to the reduced voltage\nloss.\nAdded discussion in main text P21:\n“All these strategies can be well described by design rules of increasing the emission\nof CT states or S states.69 Based on these insights, we process the ternary system,\nthat the incorporation of PD modulates the population of P-interface in ternary device\nwith the comparison to its PD:SMA binary counterpart. The most optimized device\nachieves 20 meV increase in V and over 18% efficiency, with no sacrifice in J and\nOC SC\nFF, and without the need for additives or other special treatments (Figure 5f). We\ncautiously attribute this increase to the increased population of P-interface and then\nthe suppression of EPC (Figure 6a and 6b), facilitating more emissive CT states and\nminimized non-radiative energy losses.”\nFigure 6. Mechanism diagram and universality of more pronounced P-interface with\nweaker EPC reducing non-radiative voltage loss in OPVs. (a) the calculated S factor\nvalue of SMA, PA and ternary systems, (b) the calculated ΔrDoC of SMA, PA and\nTernary systems\n12.The exciton lifetime kinetics in Fig. S36 appear to be influenced by the instrument\nresponse function (IRF). Moreover, the authors analyze charge generation on timescales\nmuch faster than that shown in Fig. S36. It is recommended to conduct TRPL\nmeasurements with a shorter time resolution and correlate those results to the charge\ngeneration process.\nResponse: We thank the reviewer for the insightful comments and suggestions. We\nmeasure the TRPL based on streak camera which shows shorter IRF about 20 ps. We\nutilized the similar fluence for TAS measurement. We found a similar trend with\nTCSPC results that PYIT shows shorter exciton lifetime. The different lifetime from\nTCSPC and streak camera originates to be the different laser power. For TCSPC,\nwe\nusually use a diode ns pulse laser as light source, which usually possesses lower fluence\ncompared to the fs-laser for streak camera measurement. However, it is quite hard to\nlower down the fluence of streak camera measurement since the sensitivity of NIR\ndetector and streak tube is not as high as PMT for single photon detection. Therefore,\nit might be hard to compare the TCSPC results with streak camera results.\nAdded information in SI:\n“Time-resolved photoluminescence (TRPL). The lifetime of neat films were carried\nout on a DeltaFlex TCSPC Lifetime spectrometer (Horiba), using a laser diode with a\npump wavelength of 447 nm. The shorter TRPL lifetime of neat films were carried out\non a home-built TRPL setup based on Ultrafast laser pulses (800 nm, ~ 35 fs pulse\nduration, 7 W) was generated by 1 kHz Ti:Sapphire regenerative amplifier (Astrella,\nCoherent, USA) and streak camera (C16910-02, Hamamatsu).”\nFigure S50. TRPL decay of neat eC9 and PYIT from streak camera (left) and TCSPC\n(right).\nReviewer #2:\nThe manuscript by Luo et al. investigates the role of penetrated donor-acceptor (D:A)\ninterfaces in modulating electron–phonon coupling (EPC) and its impact on energy loss\nin organic solar cells (OSCs). The authors strategically employ a combination of a\npolymer acceptor and a small molecule acceptor with D18 as the donor in varying ratios\nof acceptors to tune the D:A interface morphology. Two interfacial configurations,\ndesignated as E-interface and P-interface, are identified using various X-ray scattering\ntechniques and supported by transient absorption spectroscopy (TAS). EPC is further\nexplored through theoretical calculations, and its relationship to voltage loss is\ndiscussed.\nWhile the study provides an alternative perspective on D:A interface morphology and\nits influence on voltage loss, the manuscript suffers from significant complexity and\nlacks a clear narrative. The core findings are diluted by the inclusion of extraneous data\nand overly intricate analyses, which obscure the primary message. Below are several\nmajor concerns that need to be addressed:\nWe thank the reviewer for the positive comments on this work. We have outlined our\npoint-by-point responses to the comments/suggestions made by Reviewer #2 below.\n1. The transition from edge-on to face-on molecular packing at the D:A interface—\ninduced by varying the acceptor-to-donor ratio—likely alters the interfacial energetics\nbeyond changes in the optical bandgap. These energetic shifts are critical to\nunderstanding voltage losses but are not directly measured or discussed. A more\naccurate assessment could be achieved using in-situ cyclic voltammetry (CV) combined\nwith absorption spectroscopy to estimate the energy levels and offsets at the D:A\ninterface. (Energy Environ. Sci., 2024, 17, 6676-6697)\nResponse: We thank the reviewer for the insightful comments and suggestions. We\nmeasured the in-situ SEC for quantifying the HUMO level and ΔHOMO at interface.\nDetailed discussion can be found in following information. In a word, the decreased\nHUMO by increasing the D:A ratio from neat to 10:10 ratio agrees the packing\nD18\norientation transition from edge-on to face-on (J. Mater. Chem. C, 2022,10, 11565-\n11578). The interfacial HUMO offset reduced for both systems compared to neat\nHUMO offset, indicating the changed interfacial energetics. This energetic change may\nsupport the band bending at interface which increases the CT state energy. Besides, the\nvalue of HUMO offset is about 0.22 eV which would be sufficient for exciton\ndissociation (Energy Environ. Sci., 2024, 17, 6676-6697). The evolutional trend of\nHUMO in eC9 blends indicates a transition completed at an early stage (before 10:5,\nD18\nsimilar to GIWAXS analysis), while the continuously decreased HUMO in PYIT\nD18\nblends tells the consistent transition. Besides, the smaller ΔHUMO at interface than at\nneat indicates an uphill energy landscape transition from pure domain to interface,\nsupporting the previous UPS deconvolution and analysis.\nAdded information in main text at P6:\n“We perform the in-situ spectroelectrochemistry (SEC) measurement, the in-situ cyclic\nvoltammetry with UV-vis-NIR spectroscopy, to determine the energy level of interface\nunder different D:A ratio.7,8,10 By comparison, the disordered phase (interface) exhibits\nshallower HOMO depth than the pure acceptor (represented by pristine acceptor) and\nsmaller ΔHOMO difference (ΔHOMO) between donor and acceptor, indicating a uphill\nenergy landscape transition from pure domain to interface, also supporting by the\ndeconvolution of UPS spectra (Figure S7 – S11).11–13 Interestingly, the PA system shows\ncontinuously shallowed ΔHOMO, which might link to the morphology evolution.32”\nAdded information in main text at P8:\n“Additionally, the evolution of Herman’s Orientation parameter (H) confirms the same\ntrends, transition from edge-on to face-on orientation, supporting by the HUMO (IE)\nlevel shifting measured from in-situ SEC (Figure 2a, 2b, S9 and S22, and Note S1).14\nThis phase transition can also be observed from charge transport mobility evolution\nboth in In-plane (IP) and out-of-plane (OOP) direction measured from OFET and OPV\ndevices (Figure S24).”\nAdded information in SI:\nFigure S8. (a) and (b) Absorption spectra recorded during cyclic voltammetry (in-situ\nSEC) of the neat films of D18, eC9 and PY-IT in the neutral form (dark line) and the\nradical cation form (dash line). (c) Ionization energies (IE or HUMO) of donor and\nacceptor measured in the blends. (d) the IE offsets ΔIE (or ΔHUMO) as determined\nfrom the data in (b).\nDiscussion: We performed the in-situ cyclic voltammetry with UV-vis-NIR spectroscopy, to\nanalyse the HOMOs (IEs) of two systems with different D:A ratio, 10:2, 10:5 and 10:10, with\nidentical preparation as used for the solar cell characterization with ITO as the substrate (Figure\nS9-S11). This technique has been proven to be useful in terms of mapping the spectral evolution\nduring charging in electrochemical experiments and determining the oxidation onsets from the\nspectral onset of neutral and first charged species. We focus on the oxidation of the blend films\nwhich involves the potential scan to positive potentials. From the oxidation of donor and\nacceptor, the HOMOs and HOMOs difference (ΔHOMOs) can be calculated. The oxidation of\nneat films of the single component (identical preparation as for blends) was done in parallel\nand is used to help identify characteristic absorption band in the blends. During a positive\npotential sweep, the neutral absorption bands of D180 at 570 nm and 620 nm decrease and a\nbroad bathochromically shifted band is appearing with its peak at 840 nm, indicating the radical\ncation form D18+. One can also clearly identify a characteristic isosbestic point at ~ 615 nm.\nFor neat acceptor, the spectral response during cyclic voltammetry is a decrease of main peak\n(~807 nm for PYIT0 and ~840 for eC90) band of the neutral molecule and the appearance of a\nnew hypsochromically shifted band maximum at 750 nm, which is assigned to the formation of\nthe radical cation form eC9+ and PYIT+.\nThe spectra of six blends (Figure S10-S11 left) during oxidation are shown in the potential\nrange between 0.00 and ∼1.00 V vs. Fc/Fc+, and the intensity evolution of characteristic\nabsorption bands is highlighted (Figure S10-S11 right). For L :Y5,\nPM6\nincreasing the potential from 0.00 V (black spectrum) to max voltage (red spectrum)\ngoes along with a decrease of the intensity of the absorption maximum at 580 nm which\nis characteristic for the continuous oxidation of the neutral D180. Parallel to this, the\nincrease of absorption at 690 and 900 nm indicates the formation of the radical cation D18+.\nConsistent with the spectra evolution of neat D18 an isosbestic point at ~613 nm can be\nobserved in this potential range. The peak evolutions can be used to determine the oxidation\nonsets via the tangent method. This method involves the transfer of the potential onsets to the\nFermi scale with a correction factor of −4.8 eV. Hereby, the bands at 580 nm are used to\ndetermine the oxidation onset Eox of D18, which gives PYIT system, IE = −5.1 eV,\non\nIE = −5.12 eV, and IE = −5.14 eV; and eC9 system, IE = −5.13 eV,\nD-PA,10:2 D-PA,10:5 D-PA,10:10\nIE = −5.15 eV, and IE = −5.15 eV. Increasing the potential continuously, the\nD-SMA,10:2 D-SMA,10:5 D-SMA,10:10\nband at 780 nm is decreasing, showing the oxidation of neutral eC90 and PYIT0 to the radical\ncation eC9+ and PYIT+. Unfortunately, the oxidation of acceptors go along with an overall\ndecrease of the absorption between 600 and 900 nm, which aggravates the determination of the\nexact oxidation onset from these spectra. We, therefore, base the determination of the\noxidation onset Eox (eC9 and PYIT) of acceptor on the absorption at the isosbestic point of\non\nD18 in the blend at ~613 nm, which yields a value of PYIT systems IE = −5.4 eV,\nPA,10:2\nIE = −5.38 eV, and IE = −5.37 eV; and eC9 systems IE = −5.37 eV,\nPA,10:5 PA,10:10 SMA,10:2\nIE = −5.36 eV, and IE = −5.35 eV (Figure S9c). Figure S9c and d plots the\nSMA,10:5 SMA,10:10\nionization energies of the six blends. The decreased HUMO by increasing the D:A ratio\nD18\nagrees the packing orientation transition from edge-on to phase-on. The evolutional trend of\nHUMO in eC9 blends indicates a transition completed at an early stage (before 10:5,\nD18\nsimilar to GIWAXS analysis), while the continuously decreased HUMO in PYIT\nD18\nblends tells the consistent transition. Besides, the smaller ΔHUMO at interface than at\nneat indicates an uphill energy landscape transition from pure domain to interface,\nsupporting the previous UPS deconvolution and analysis.\nFigure S9. Absorption spectra (left) for selected potentials recorded during oxidation, and the\ncorresponding peak trends (right) for D18:eC9 with 10:2, 10:5, and 10:10 D:A ratio (top to\ndown).\nFigure S10. Absorption spectra (left) for selected potentials recorded during oxidation, and\nthe corresponding peak trends (right) for D18:PYIT with 10:2, 10:5, and 10:10 D:A ratio (top\nto down).\nAdded information in SI (Methods):\nSpectroelectrochemistry (in-situ SEC). The spectroelectrochemical measurements\nwere taken place with a three-electrode setup under nitrogen atmosphere. The blends\nwith ITO coated glass as base substrate were used as working electrode, a platinum\nwire as counter electrode and a silver chloride covered silver wire as pseudo reference\nelectrode. All the potentials were referenced to the ferrocene/ferrocenium (Fc/Fc+)\nredox potential, added after the measurements. The electrochemical cell contain MeCN\nas solvent and TBAPF6 (0.1 molar) as conducting salt as standard electrolyte. The UV-\nvis measurements were performed in transmission mode through the working electrode.\nFor each data point in the cyclic voltammogram, a spectrum was measured. The\npotentials were applied by an PGSTAT302N potentiostat, purchased by Metrohm. The\nUV vis spectra were measured by an HR-6XR600-25 spectrometer, OceanOptics. The\nlight source is a CEL-PF300UV halogen lamp.\n2. The assignment of the CT-state emission appears problematic. The manuscript\nreports CT emission that is blue-shifted relative to the local excitation (LE) emission of\nthe low-bandgap component, which contradicts the fundamental understanding that CT\nstates typically lie below LE states. This discrepancy raises concerns about the accuracy\nof the spectral deconvolution or the identification of the emissive states. The authors\nmust revisit this analysis with greater care.\nResponse: We thank the reviewer for the insightful comments and suggestions. We\nagree that the assignment of the CTS emissions is quite strange, which has also\nconfused us at very first time. However, considering the Marcus theory framework,\nthese strange shapes are rare but not entirely impossible, since the shapes are strongly\ndependent on reorganization energy. We did the simulation showing that the larger\nreorganization energy (  ) might induce the red shift and broaden of CTS emissions\n \n(Fig. R). Considering the relatively low reorganization energy of our system, we believe\nthis shape is possible theoretically. In fact, our fitted CT state energy is still lower than\nthe corresponding singlet emission. Besides, this EL analysis method also has been\nutilized in previous analysis showing that CT states emission is settled at lower energy\nside of singlet emission (Energy Environ. Sci., 2023, 16, 3416–3429).\nFigure R4. Simulation of CTS EL spectra on Marcus formalism with variable re-\norganization energy. This result is defined using a constant CTS energy of 1.36 eV.\nNonetheless, this constant will not have any influence on the relevant interpretations\ndone.\nWe also argue that the interfacial band bending might slightly increase the CTS energy,\nleading to the blue shift of CT emissions. According to Laquai. et. al, and Kim. et. al.\n(Nat. Mater. 20, 378–384 (2021); Nat Commun 14, 1870 (2023)), the interfacial\nquadruple moment of donor and NFAs creates the gradual change in the electrostatic\npotential forcing the energy level bending (Fig. R). The energy level bending increases\nthe CT states energy and narrows the LUMO (or IE) difference (ΔLUMO or ΔIE). This\nnarrowed ΔLUMO can also be observed by SEC analysis (in-situ cyclic voltammetry\n(CV) combined with absorption spectroscopy), wherein the measured ΔLUMO of blend\nis about ~0.3 eV (partially replacing the interfacial property) lower than the ΔLUMO\nof neat donor and acceptor films (~0.5 meV). As both HOMO and LUMO are bent in\nthe same direction, the energy gap keeps the same within donor or acceptor. Our fitted\nCT state energy is actually lower than singlet state energy (or LE states). We cautiously\ndiscuss that these CT states emission shapes are potentially originated from the smaller\nreorganization energy and energy level bending.\nFigure R5. Schematic representation of the difference between the acceptor exciton\nenergy E A and the interfacial CT state energy, E , and their relation to the LOMO\ng CT\ndifference (or ionization energy offset ΔIE). B is the energy bending (Adv. Mater.\nInterfaces 2023, 10, 2202515).\nCertainly, according to our CT state energy fitting approach, the emission of neat\nacceptors is also a dominant component. As the external EL of the devices is almost\nentirely determined by the Y6 singlet excitons, we compared the PL and EL of the neat\nacceptors in device geometry. Notably, we performed the PL at SC condition, which\nshows same spectra at V condition (ACS Energy Lett. 2021, 6, 557−564). We found\nOC\nthat EL and PL show similar spectra shapes indicating that the singlet emission is\nactually settled at lower energy side agreeing with the analysis. We believe that the\nreasons for the “higher energy CT states” are complicated and needed to be discussed\nmore in further studies.\nAdded information in SI:\nFigure S35. The comparison between singlet emission and CT state emission for two\nsystems. The CT state emissions are at the blue side of S emission (measured by EL\n1\nand PL at SC condition). Therefore, for later fitting, our CTS emissions are always on\nthe blue side of singlet.\n3. While analyzing non-radiative voltage losses across different blend ratios (10:1 to\n10:15 for EC9 and PYIT), the authors do not account for the potential impact of LE-\nCT energy offset changes or hybridization effects. These factors are known to\ncontribute significantly to voltage loss and should be included in the discussion or\nanalysis.\nResponse: We thank the reviewer for the insightful comments and suggestions. We\ntotally agree that hybridization between S and CT states strongly affects the reduction\n1\nof non-radiative energy loss, which has been proved in many previous studies (J. Am.\nChem. Soc. 2019, 141, 6362−6374; Nat Energy 2021, 6, 799–806; Energy Environ. Sci.,\n2024,17, 6676-6697). According to Nelson et. al. and Gao et. al., the recent high\nefficient systems, such as PM6:Y6, show relatively efficient charge generation despite\na very small energy offset, ΔE . The previous studies, especially the fullerene-based\nS1-CT\nsystems, proposed the necessary driving energy to be around 0.3 eV, limiting the\nmaximum achievable V . Besides, the achieved V in D-A organic photovoltaic\nOC OC\ndevices is also limited by the magnitude of the potential loss due to the radiative and\nnonradiative recombination pathway of CT states. The current understandings declare\nthat the formation of free charges from CT states directly competes with the radiative\nand nonradiative recombination of the bound electron-hole pairs (CT states) to the\nground states.\nThe findings from Nelson et. al., appear to be relatively suitable for predicting non-\nradiative energy loss in high energy offset systems (fullerene-based) but unsuccessful\nto predict many recent low ΔE systems which show qV about the order of 100\nS1-CT nr\nmeV lower than predicted. Bixon et al. have previously quantitated the mixing of local\nexcited singlet (S ) state and CT states due to the intensity-borrowing mechanism (J.\nelectronic part of radiative and non-radiative coupling not only consists of the transition\ndipole moment and electronic coupling between CT and S state (  and   ),\n1   -   CT-  \nbut also an additional modulation term (the detail can be found in Note S6). The\nadditional term of radiative part depends on the transition dipole moment between S\n0\nstate and S state (  ), the electronic coupling between S and CT state (  ),\n1   -   1   -  \nand ΔE (Eq. R1), while the non-radiative part depends on the electronic coupling\nS1-CT\nbetween S and S state (  ), between S and CT state, and ΔE (Eq. R2). By\n1 0   -   1 S1-CT\nusing the generalized Mullikan-Hush method, the transition dipole moment can be\nrelated to electronic coupling in Eq. R3.\n \n                 ⃗ ∗ \n  = CT-   (             ⃗ +   -     -   )     (  ) (1)\n ,      3   ℏ c3 CT-   ∆  CT-  \n    -  \n \n  ,     \n \n2     \n=    +\n  -     -  \n      (0) (2)\nℏ CT-   ∆ \n  -  \n   \ni-     \n  = (3)\n - \n ∆    +4   \ni-  i- \nWhere the   describes the static dipole moment between two states. We conclude\n - \nthat the hybridization between two states mainly influences the electronic coupling\nterms but the Franck-Condon weighted density of states (FCWD). Therefore, it is\npossible for us to calculate the transition dipole moment and the electronic coupling\nfrom theoretical calculation and experiments. To calculate the   , we come to the\n  -  \ncharge transfer rate from transient absorption spectroscopy (TAS). The classical Marcus\nelectron transfer Model (Eq. R4) successfully describes the exciton dissociation rate\nconstants (   ) which fitted from charge generation kinetics from TAS (Nat\nCommun 2022, 13, 2598, Nat Commun 2020, 11, 833). We obtained the   and  \n   \nwhich represents the E-interface-related transfer rate and P-interface-related rates\n(Figure 3a and S26).\n \n1 2     +∆   \n=    exp (−         ) (2)\n  ℏ 4             -   4         \nWhere   , the Bolzmann constant;  , the temperature (    ~ 26    );   , the outer\n     \nreorganization energy. By fitting the EL spectra, we obtained the   and   . By\n    \nfinding the crossing point of absorption and PL spectra, we obtained the   .\nThe  \ndifference between   and   is ∆  (Table S4). Therefore, we calculated\n           \nthe   of P-interface and E-interface for each D:A ratio blends of PA and SMA\n  -  \nsystems. From theoretical calculation from TD-DFT, we obtained the transition dipole\nmoment from two different CT states to ground states (Table S11). After we obtained\nall parameters, we utilized Eq. R1-2, 4 to calculate the non-radiative energy loss and\ncompared the calculated qΔV with experiment qΔV shown in Fig. 5d-e.\nnr nr\nTo understanding the effect from hybridization, we mainly focus on the electronic part\nof radiative and non-radiative coupling, including   ,   , and   . The\n  -   CT-     -  \nelectronic couplings are strongly related to ΔE (Figure S55). The small ΔE\nS1-CT S1-CT\nmay supress the effects from electronic couplings, in which situation the increasing of\nFCWD(0) and FCWD(E ) may dominant the k and k . When we set the ΔE to\nCT-S0 nr r S1-CT\nbe 100 meV, the increase of t from 10 meV to 100 meV gives rise to a 77 meV V\nS1-CT OC\nincrease, while the reduction of t and t from 300 meV to 20 meV exhibit 30\nS1-S0 CT-S0\nmeV and 90 meV V increase, respectively. When we reset the ΔE to 50 meV, the\nOC S1-CT\nsame variations induce 61 meV, 43 meV and 62 meV V increase, respectively.\nOC\nTherefore, the reduction of t and increase of t almost contributes the same on\nCT-S0 S1-CT\nincreasing V , while the reduction of t shows smallest effect on increasing V .\nOC S1-S0 OC\nIn a word, t and t need to be controlled, keeping as higher t as possible\nS1-CT CT-S0 S1-CT\naccording to the intensity borrowing mechanism (Nature Mater 2018, 17, 703–709) and\nsmaller t . This is because although the larger t brings the faster   , the\nCT-S0 CT-S0  ,     \n  also increase and even compensating the increase of   leading to\n  ,       ,     \nlarger qΔV .\nnr\nApart from the theoretical calculations, we then focus on the experiment results of PA\nand SMA systems. To find out the contribution of hybridization on two systems, we\ndefined the electronic part of radiative coupling as effective transition dipole moment,\n ∗ =              ⃗ + \n      \n \n   \n \n  -  \n \n  \n \n ⃗ ∗   -  ,\nand effective electronic coupling,  ∗ =   +\nCT-   CT-  \n∆   -  \nCT-   CT-  \n   -      -   . Therefore, we can re-construct   ∝  ∗   and   ∝\n∆   -  \n ,      CT-     ,     \n ∗   . Here, to analyse hybridization, we assume that all ratio has same amount of P-\nCT-  \nand E-interface to rule out the effects from reorganization energy, EPC and others. The\ncalculated   and   can be found in Figure S577. The corresponding\n ,        ,     \nΔV has also been shown in Figure S59 according to Eq. 1. To simplify the calculation,\nnr\nwe can rewrite the Eq 1 as Δ  ∝ ln 1+   C ∗ T-     ×     , where   and   is the\n    ∗    \nCT-  \ncomponents excepting electronic part for   and   respectively. We\n  ,       ,     \n ∗  \ndefine CT-   as the hybridization factor, exhibiting the smaller factor meaning the\n ∗  \nCT-  \nstronger hybridization results in small Δ  . In previous calculation, value of  \n  \ntypically two to four orders of magnitude greater than that of   by increasing S from\n0.8 to 1.3. We show the plot for two systems with E-and P-interface (Figure S57), where\nthe red and blue lines represent the simulated qΔV calculated by their corresponding\nnr\nelectronic part and others. While the grey dot lines represent the qΔV calculated by\nnr\nchanging the electronic part to the value of their counterpart interfaces. Two systems\nboth show the qΔV decrease of ~ 8 meV by replacing E-interface related electronic\nnr\npart to P-interface related part. Therefore, because of the stronger hybridization in P-\ninterface, it gives rise to the 8 meV qΔV decrease. In total, P-interface dominant\nnr\ndevices for PA and SMA system (D:A = 10:15) exhibit ~28 meV (Figure S54) lower\nqΔV than E-interface dominant devices (10:1), attributable to the smaller\nnr\nreorganization energy and stronger hybridization of P-interface. By calculation, we find\nthat, for two systems, we argue this weak effect arising from hybridization to be\nattributable to the non-significant changes in electron coupling (  ) between S and\n  -   1\nCT states. Here the effects from hybridization can be partially ignored in comparison\nto the effects from EPC.\nAdded discussion in main text on Page 20 and Page 21:\n“Beyond EPC, prior studies have identified that parameters such as, ∆  ,   ,\n  -     \n  , and   , also contribute to the reduction of qΔV .49,62 It is therefore crucial to\n  -     nr\ndistinguish the individual contribution of each parameter to qΔV . Regardless of the\nnr\nEPC, the reduction in qΔV achieved by lowering   is independent of the change of\nnr  \n∆  , whereas V increases by varying the   ,   , and   are as the\n  -   OC   -     -        \nfunctions of ∆  (Figure S61 and Table S10-11). Specifically, the V increase by\n  -   OC\nreducing   , from 200 meV to 100 meV, remains consistent, as ~ 85 meV. Conversely,\n \nthe positive impact of modulating electronic couplings (or transition dipole moment)\non V is gradually diminishes as ∆  decreases. However, this diminishing effect\nOC   -  \ncould be counteracted by reducing EPC which is isolated from ∆  (Figure S62\n  -  \nand Table S12-13). Such a reduction of EPC might further enhance the molecular\nPLQY and EQE ,63 and is also independent of ∆  , presenting a potential strategy\nEL   -  \nfor supressing non-radiative energy loss of OSCs.\nThe non-radiative energy losses in the two systems were analysed following the insights\nfrom numerical simulations. Calculation of the recombination rates,   ,\n ,     \n  , and qΔV as functions of EPC based on the experimental parameters (Table\n  ,      nr\nS7) show a consistent ~28 meV lower qΔV for P-interface dominant devices\nnr\n(D:A=10:15) compared to E-interface dominant ones (D:A=10:1) across both PA and\nSMA systems (Figures 5d, 5e, S63). Attribution of this reduction points to the smaller\nreorganization energy and stronger hybridization effects of P-interface. Decomposition\nof the contributions confirm   as the dominant factor, consistent with simulations\n \n(Figure S64). It is notable that the reducing of ∆  might enhance both the\n  -  \nelectronic part of   and   , making careful balancing of them essential. Similarly,\n    \nreplacing SMA with PA reduces qΔV by ~25 meV also due to the smaller ∆ \nnr   -  \nand larger   leading to enhanced S -CT state hybridization, and smaller   .”\n  -   1  \n“…However, the achieved reductions (~25 meV and ~ 28 meV) are unable to fully\naccount for the observed qΔV in devices with varying D:A ratios (~ 55 meV for PA\nnr\nsystem and ~ 38 meV for SMA system between 10:1 and 10:15 devices) and replacing\nSMA to PA system (~63 meV between 10:15 devices).”\nAdded Notes, discussion, and plots in SI:\nNote S6\nBy considering hybridization, the electronic part of radiative and non-radiative\ncoupling not only consists of the transition dipole moment and electronic coupling\nbetween CT and S state (  and   ), but also an additional modulation term\n1   -   CT-  \n(the detail can be found in Note S6). The additional term of radiative part depends on\nthe transition dipole moment between S state and S state (  ) , the electronic\n0 1   -  \ncoupling between S and CT state (  ) , and ΔE (Eq. R1), while the non-\n1   -   S1-CT\nradiative part depends on the electronic coupling between S and S state (  ) ,\n1 0   -  \nbetween S and CT state, and ΔE (Eq. R2). By using the generalized Mullikan-Hush\nmethod, the transition dipole moment can be related to electronic coupling in Eq. R3.\n \n - \n   \ni-     \n= (19)\n ∆    +4   \ni-  i- \nWhere the   describes the static dipole moment between two states. We conclude\n - \nthat the hybridization between two states mainly influences the electronic coupling\nterms but the Franck-Condon weighted density of states (FCWD). Therefore, it is\npossible for us to calculate the transition dipole moment and the electronic coupling\nfrom theoretical calculation and experiments.\nTo further understand the effects from hybridization, we defined the electronic part of\nradiative coupling as effective transition dipole moment:\n            ⃗ ∗ \n ∗ =              ⃗ +   -     -   (20)\nCT-   CT-   ∆ \n  -  \nThe electronic part of non-radiative coupling as effective electronic coupling:\n   \n ∗ =   +   -     -   (21)\nCT-   CT-   ∆ \n  -  \nTherefore, we can re-construct   =  ∗ ∗   and   =  ∗ ∗   ,\n ,      CT-     ,      CT-  \nwhere   and   is the components excepting electronic part for   and\n  ,     \n  respectively. To simplify the calculation, we can rewrite the Eq 1 as:\n ,     \n ∗    \n   ∝    1+\nCT-  \n×   (22)\n    ∗    \nCT-  \n ∗  \nWe define CT-   as the hybridization factor. The smaller factor indicates the\n ∗  \nCT-  \nstronger hybridization resulting in small    .\n  \nFigure S11.The change of non-radiative energy loss qΔV by reducing λ , t , t ,\nnr 0 S1-CT S1-S0\nand t\nCT-S0.\nTable S2. Potential V increasing when changing different parameters when S = 1\nOC\nand ΔE = 100 meV.\nS1-CT\nParameter improvement strategy V increase\nOC\nReduce the outer reorganization energy ( ) from 0.2 to 0.1 eV 85 meV\no\nIncrease the electronic coupling between S and CT state (t\n) 77 meV\nCT\nfrom 0.01 eV to 0.1 eV\nReduce the electronic coupling between S and S state (t )\n1 0 S1-S0\n30 meV\nfrom 0.3 eV to 0.025 eV\nReduce the electronic coupling between CT and S state (t )\n90 meV\nfrom 0.3 eV to 0.025 eV\nTable S3. Potential V increasing when changing different parameters when S = 1\nOC\nand ΔE = 50 meV.\nS1-CT\nParameter improvement strategy V increase\nOC\nReduce the outer reorganization energy ( ) from 0.2 to 0.1 eV 83 meV\no\nIncrease the electronic coupling between S and CT state (t\n) 61 meV\nCT\nfrom 0.01 eV to 0.1 eV\nReduce the electronic coupling between S and S state (t )\n1 0 S1-S0\n43 meV\nfrom 0.3 eV to 0.025 eV\nReduce the electronic coupling between CT and S state (t )\n62 meV\nfrom 0.3 eV to 0.025 eV\nFigure S12. Simulated qΔV for two systems by modifying hybridization. To simplify\nnr\nthe calculation, we can rewrite the Eq 1 as   ∝    1+   C ∗ T-     ×    , where   and\n    ∗    \nCT-  \n  is the components excepting electronic part for   and  \n  ,       ,     \nrespectively. In previous calculation, value of   typically two to four orders of\nmagnitude greater than that of   by increasing S from 0.8 to 1.3. We then show the\nplot for two systems with E-and P-interface, where the red and blue lines represent the\nsimulated qΔV calculated by their corresponding electronic part and others. While\nnr\nthe grey dot lines represent the qΔV calculated by changing the electronic part to the\nnr\nvalue of their counterpart interfaces. Two systems both show the qΔV decrease of ~ 8\nnr\nmeV by replacing E-interface related electronic part to P-interface related part which\nshows smaller hybridization factor (Notes S6). Therefore, because of the stronger\nhybridization in P-interface, it gives rise to the 8 meV qΔV decrease.\nnr\n4. At low acceptor concentrations (e.g., 10:1), the device is heavily donor-rich (D18-\ndominant). Given D18 known as high photoluminescence quantum yield and\ndocumented EQE values of ~1.23% DOI: [10.1038/s41467-025-58352-x], it is\nEL\nimportant to examine whether the increased voltage losses arise from poor electrode\nwork function alignment. Have the authors considered testing alternative device\narchitectures or interlayers to rule out electrode-induced misalignment as a source of\nloss?\nResponse: We thank the reviewer for the insightful comments and suggestions. We\nagree that D18 with high PLQY should show large EQE . The increased voltage losses\nEL\nmight arise from the poor electrode work function alignment. Therefore, we chose\nanother two electron transporting layers, PDINN-F3N and PDINN, and tested the\nEQE of devices with low D:A ratio, (10:1 to 10:5). We did not change the hole\nEL\ntransporting layer, PEDOT:PSS. This material has been proved to be efficient for hole\ntransport and extraction, especially also been used for OLED devices (Nat Commun 16,\n3176 (2025)). The electron transporting layers we selected include small molecules\n(PDINN) and also polymers (PNDIT-F3N, PFN-Br). They both modified the work\nfunction of metal cathode forcing small extraction barriers and efficient charge\nextraction. The electron effectively injects into the modified electrode directly.\nAccording to literatures, by contact with Ag, PNDIT-F3N, PFN-Br, PDINN, modify the\nwork function of Ag to −3.91 eV, −3.86 eV, −3.83 eV (Adv. Sci. 2022, 9, 2105575.,\nJournal of Energy Chemistry 2025, 105, 835–842). However, their own LUMO levels\nshow huge difference, which means they can be regarded as different categories with\ndifferent work functions. We found almost same EQE value for low D:A ratio devices\nEL\nfor three interlayers. We argue that the larger voltage losses might not originate from\npoor electrode work function alignment.\nWe then plot the EL spectra including neat donor, neat acceptor, and their lower D:A\nratio blends (Figure S). It is obvious that although blue shifting observed compares to\nneat film, they are still very far from donor EL. This indicates the emission still\noriginated from the donor:acceptor interface. Our transient absorption spectroscopy\nalso agrees with these results that we observed charge transfer-induced donor GSB\npeaks where we only excite acceptor but donor. We also would like to claim that the\nmorphology of blends, even at low D:A ratio, is quite different from that of blends. Our\nresults indicate that the well-packed D18 structure is broken by the incorporation of\nacceptors. As the existence of E-interface, the fast charge transfer will occur, where the\nCT state might still dominate the charge generation kinetic in low D:A ratio blends.\nSalleo et. al. observed similar trend at low D:A ratio PM6:Y6 blend. The measured ΔV\nnr\nat low D:A ratio device shows value of over 0.3 meV, which is even higher than ours.\nThe observed obvious CT states emission and absorption at low D:A ratio, which means\nthe CT states still play the important role in low D:A ratio device (Adv. Energy Mater.\n2023, 13, 2204297). Liu et. al. also observed decreased trend of V by increase the\nOC\nD:A ratio (Energy Environ. Sci., 2022, 15, 3483–3493). Both Salleo et. al. and Liu et.\nal. reported the morphology change by continuously increasing the acceptor proportion.\nLiu et. al. investigated that when acceptor content increases from 10% to 50%, the\nPLQY of donor (PLQ ) gradually increases from 53% to 95%. This might also describe\nD\nwhy the donor dominates devices show larger ΔV . D18 shows very strong PLQY, the\nnr\nincorporation of acceptor breaks the D18 packing and forms the E-interface (amorphous\nintermix interface) for charge transfer.\nFigure R6. The EL spectra for neat D18, neat PY-IT, and neat eC9, along with their 10:1\nD:A ratio device.\nAdded discussion in main text on Page 19:\n“…. The employment of different transport layers confirms these decreasing trends, indicating\nthat the energy loss arises not from the interlayers but from the interfaces of the active layer\n(Figure S59-S60).”\nAdded plot in SI:\nFigure S13. The device architecture and the energy level of those different layers\ninclude the utilized three different electron transport layers. The measured EQE show\nEL\nsimilar values for three types of devices.\nFigure S14. EQE results for SMA system and PA system with D:A ratio increasing\nEL\nfrom 10:1 to 10:15.\n5. The inclusion of PYIT as a third component reportedly improves the V by only\nOC\n~20 meV. Such a modest enhancement is neither novel nor significant, given the\nextensive prior literature that has established similar ternary effects and underlying\nphysical mechanisms e.g., DOI: [10.1038/s41560-023-01309-5]. The authors should\nclarify how this finding advances existing knowledge.\nResponse: We thank the reviewer for this insightful comment. We agree that a ~20 meV\nincrease in V , in itself, is a commonly observed effect in ternary organic solar cells\nOC\n(OSCs), and the underlying mechanisms have been systematically studied, e.g., in the\nwork by Gao et al. (Nat Energy 2023, 8, 978–988). However, we employed a Layer-by-\nLayer (LBL) deposition method, which fundamentally differs from the bulk\nheterojunction (BHJ) approach systematically studied in prior literature (Nat\nEnergy 2023, 8, 978–988). As established in our previous work (Joule 2024, 8, 509–\n526), this method forms a well-defined p-i-n structure. PAs with strong entangled chains\nare able to strengthen the stratification, limiting the movement downward of SMAs into\nthe swelled spaces of bottom PD layers. We can artificially engineer an adjustable\ninterfacial region (i-region) by subsequently incorporating PY-IT into the\nD18:eC9 matrix, thereby modulating the donor-acceptor interpenetration and then\nincreasing the P-interface. This level of interfacial control is difficult to achieve with\ntraditional BHJ methods.\nBesides, Gao et. al. proposed two insightful design rules to further improve the V in\nOC\nternary systems, 1) a high PLQY guest binary blend and similar CT-state energies\nbetween the two binary blends; 2) a high miscibility between the guest component and\nthe low gap component in the host binary blends (Nat Energy 2023, 8, 978–988). They\npredicted about 20 meV increase of V in Case-1. However, for our situation, to\nOC\nachieve highest PCE, we only include 20% PY-IT to avoid the sacrifice of J and FF.\nSC\nAs shown in Figure 5f and S60, and Table S15, we kept the J and FF with additional\nSC\n20 meV V increasing. Our previous study also utilized similar ternary system but\nOC\ndifferent PD, PM6, achieving about 40 meV V increasing when increasing the PA\nOC\nratio to 40% (Table R1, Joule 2024, 8, 509–526).\nTable R1: Photovoltaic parameters of PM6:BTP-eC9:PY-IT based LBL-type OSCs\nwith varied weight ratios of PY-IT (Joule 2024, 8, 509–526).\nPM6:PYIT:eC9 V (V) J (mA cm-2) FF (%) PCE (%)\noc sc\n1:0:1 0.840 26.65 0.783 17.53\n1:0.1:1.1 0.850 27.21 0.806 18.64\n1:0.2:1 0.859 27.79 0.813 19.41\n1:0.4:0.8 0.877 26.56 0.770 17.94\n1:1:0 0.939 23.62 0.731 16.21\nIn our case, we argue that we are focusing on the effects of EPC on V from two types\nOC\nof CT states, which seem to have not been mentioned in other work. The incorporation\nof PY-IT into D18:eC9 binary introduced more P-interface which possesses lower EPC.\nAccording to MLJ equation and spontaneous emission formula, the reduction of EPC\nreduces k and increases k simultaneously, which increases the PLQY of CT states.\nnr r\nChow et. al. observed the similar results that the penetration properties of PD may\nfurther increase the PLQY by suppressing the aggregation-caused quenching (ACQ),\nwhich is the situation at interface. In Gao et. al.’s design rules (Case-1), they didn’t\ncover the effects of EPC where they set EPC as a constant, which might underestimate\nthe achievable V .\nOC\nIn a word, our results follow the Case-1 for increasing V , achieving over predicted\nOC\nincrease which might be attributed to the increased population of P-interface with lower\nEPC from the incorporation of PYIT, facilitating the enhancement of PLQY of CT states.\nWe, here, are trying to compensate for the design rule for ternary systems, that is, the\nmore pronounced P-interface might promote the emissive CT states minimizing non-\nradiative energy losses of binary and ternary systems, which can be easily achieved by\nintroducing small amounts of PAs into high PCE SMA-based systems, where the PAs\nneed to shows stronger penetration with PDs.\nAdded discussion in main text on Page 21:\n“…. In addition to the representatives of PA system, D18:PY-IT, and SMA system,\nD18:eC9, other two PA systems also exhibit larger P-interface population and smaller\nEPC than those of three SMA systems (Figure 6a and 6b). We summarize the many of\nthe reported energy losses in literatures achieved by two systems (Figure 6c). It is\nobvious that PA-based systems show potentially lower ΔV than SMA systems. We\nnr\npropose achieving low ΔV in binary system by modulating the EPC of the interface,\nnr\nparticularly by leveraging the P-interface with inherently lower EPC, which benefits\nfrom strong percolation between polymer acceptor and polymer donor.\nIn addition to the representatives of PA system, D18:PY-IT, and SMA system, D18:eC9,\nother two PA systems also exhibit larger P-interface population and smaller EPC than\nthose of three SMA systems (Figure 6a and 6b). We summarize the many of the reported\nenergy losses in literatures achieved by two systems (Figure 6c). It is obvious that PA-\nbased systems show potentially lower ΔV than SMA systems. We propose achieving\nnr\nlow ΔV in binary system by modulating the EPC of the interface, particularly by\nnr\nleveraging the P-interface with inherently lower EPC, which benefits from strong\npercolation between polymer acceptor and polymer donor.“\n6. The manuscript is presented as an investigation of EPC and its role in energy loss,\nas indicated by the title and abstract. However, the majority of the results section is\ndevoted to charge carrier dynamics with little reference to EPC or energy loss\nmechanisms. If the authors consider the charge dynamics central to the manuscript's\nmessage, they should restructure the abstract and Introduction to guide the reader\naccordingly. Alternatively, the manuscript should be refocused to stay aligned with the\nstated objective.\nResponse: We thank the reviewer for the insightful comments and suggestions. we have\nsubstantially revised the \"“Charge Generation Dynamics with the effects of P-interface”\nsection, particularly the part concerning charge generation dynamics under the\ninfluence of the P-interface, and have reorganized the corresponding descriptions. Our\nrevision de-emphasizes the details of carrier dynamics to better highlight the central\nrole of the P-interface's weak electron-phonon coupling (EPC) in reducing non-\nradiative energy loss. To characterize the two interfaces, we introduce two key\nparameters: ΔrDoC and the ratio A /A (derived from the weight coefficients in charge\n1 2\ntransfer kinetics). Since the P-interface is strongly associated with quasi-aggregates,\nwe\npropose using ΔrDoC to quantify its prevalence. Meanwhile, the A /A ratio reflects\n1 2\nthe relative contributions of the E-interface and P-interface, allowing us to estimate\ntheir respective populations. Furthermore, the electronic coupling between the S1 and\ncharge transfer (CT) states at both interfaces can be derived from the corresponding\ncharge transfer rates using Marcus theory. For this reason, our discussion still includes\na brief consideration of charge carrier behavior.\nModified discussion in abstract on Page 3:\n“Organic solar cells (OSCs) achieve 21% efficiency, yet non-radiative energy loss\n(qΔV ) remains a critical barrier to further improve the open-circuit voltage (V ).\nnr OC\nThis loss is primarily governed by the optoelectronic properties of interfacial CT states, yet the\nprecise role of electron-phonon coupling (EPC) is not fully resolved. Through analysis of\nthree all polymer OSCs and four small molecule acceptor (SMA)-based OSCs, we\nidentify two donor/acceptor (D/A) interfacial mixed phases that foster two distinct CT\nstates, establishing efficient charge generation. …… The incorporation of PA into SMA\nsystem as guest component modulates the population of P-interface reducing the EPC\nand then enhancing V .”\nOC\nModified discussion in introduction on Page 4:\n“Salleo et al. and Amassian et al. directly link NFA blend morphology and structural\norder/disorder to multi-CT states distributions and associated non-radiative\nrecombination process via systematic compositional tuning.”\nModified discussion in introduction on Page 5:\nIn this work, we investigate two emerging PD:NFA systems, PD: SMA system and PD:\nPA system, with contrasting aggregation behaviors that govern their bulk\nheterojunction (BHJ) optical and morphological landscapes. By analyzing four PD:\nSMA system and three PD: PA system, the PD:SMA systems tend to form high-purity\nacceptor domains and disordered mixed phases, whereas the PD:PA systems exhibit a\nreversed morphology comprising disordered pure domains but ordered intermixed\nphases, consistent with previous findings by Chow et al.4……The P-interface exhibit\nslight edge-on molecular orientation relative to the pure acceptor domains. ……\nBesides, P-interfaces also facilitates efficient charge generation, as seen from the\nkinetics of P-interface dominated PA systems. In performance, simulated energy loss\nanalysis reveals that these low-EPC P-interfaces reduce non-radiative energy losses by\n~58 meV, aligning with experimental reduction of energy loss (~55 meV) of PA system.\nThe achieved V increase in PA-SMA ternary system (D18:PY-IT:eC9) supports the\nOC\nstrategy to modulate the population of P-interface by incorporation PA into SMA\nsystem.”\nAdd discussion in main text on Page 12:\n“We then calculate the outer reorganization energy   for both systems by fitting the\n \nreduced electroluminance (rEL) spectra, referred by PL spectra under short-circuit\ncondition, according to modified classical Marcus theory approach (Figure S35-S38,\nTable S4-S5 and Note S2). CT state energy (E ) can also be extracted for varied D:A\nCT\nratio devices of two systems. The observed smaller   indicates the more ordered\n \ninterface in PA systems.6 E continuously decreases with increasing acceptor ratio,\nCT\nconsistent with the growing presence of the P-interface. The reduction in\nreorganization energy ( , including   and   ) is beneficial for minimizing the\n   \ndriving force for exciton dissociation by mitigating molecular distortion energy\npenalties.49”\nAdd discussion in main text on Page 13:\n“Within the Marcus framework, the non-radiative decay of excited state is strongly\ninfluenced by the molecular reorganization, describing the electron-phonon coupling\n(EPC) induced by molecular vibration and the ubiquitous disorder (Note S3).”\nAdd discussion in main text on Page 14:\n“The trends of those   might be corroborated experimentally by charge transfer\n  -  \nrates based on Marcus Theory. …… However, in addition to hybridization, the\nsignificantly distinct   in two systems (Figure 3c), forcing variable EPC and electron\ntransfer rate, may also substantially influence charge carrier dynamics and qΔV ,\nnr\naccording to Marcus Theory.”\nModified discussion in main text on Page 15:\nCharge Generation Dynamics with the effects of P-interface.\n“We perform Pump-Probe (PP) and Pump-Push-Probe (PPP) transient absorption\nspectroscopy (TAS) and to investigate charge generation dynamics at the interface and\ntrace the population dynamics of bound CTEs (Figure S43-S56).53,54 The different\nmorphology between P-interface and E-interface affects the exciton dissociation and\nalso the CTE separation. We analyse the hole transfer kinetics of donor ground-state\nbleach (GSB) signal by tri-exponential function to analyse the charge generation\nprocess (Figure 4a, S44-45, Table S6, and Notes S5).\nThe initially formatted E-interface promotes early charge generation and dominates\nthe hole transfer process, especially at low D:A ratios (10:1) (Figure 4a, light red and\nlight blue). The following P-interface formation and expansion significantly impacts\nthe subsequent charge generation as the ratio increases (10:15) (Figure 4a, dark red\nand dark blue). The evolution of the E-interface (  ) and P-interface (  ) charge\n   \ntransfer weight coefficient, quantifying the ratio of two interfaces, aligns with the\ngrowth trends of the P-interface in two systems (Figure 4b). The population of P-\ninterface in PA system is larger than that in E-interface and grows continuously, while\nin SMA system, the E-interface dominance the interface population. We argue that\ncharge generation occurs via both interfaces, E-interface (modeled at a 10:1 D:A ratio),\nand P-interface (modeled at a 10:15 D:A ratio) (Figure S46). The faster   and   in\n   \nthe PA system likely originate from more favourable values of ΔE and  . The\nS1-CT\nsmaller difference between ΔE and   leads to faster charge transfer rate\nS1-CT\naccording to classical Marcus theory, facilitating faster exciton dissociation and CTEs\ngeneration.55 We further estimated the electronic couplings between the S₁ and CT\nstates for the two interfaces,   and   (Table S7). The estimated values\n  -  ,    -  , \nagree with the trends from theoretical calculation and offer valuable insights into the\ndegree of hybridization between the two states.2 The diffusion-limited transfer time\nconstant,   , and its weight coefficient,   , increased significantly due to the growth\n   \nof pure domain sizes, leading to longer diffusion times.56 The shorter   in PA system\n \nmight due to the more gentle energy landscape between pure phase and interface,\nfacilitating exciton migration.6\nAfter studying the charge transfer process, we then examined CTE separation using\nPPP-TAS measurements, which directly probe this process (Figure S48 and Notes\nS5).57 Figure 4c presents the kinetics of the push response aligning with the electro-\nabsorption (EA) response at 610 nm (Figure S49), which confirms the presence of push-\ninduced CTE states.53 The lower normalized PPP response intensity in the PA system,\nwhich quantifies the bound CTE population, indicates a minimally retained CTE\npopulation and, therefore, efficient CTE separation. Besides, the faster decay of the\nPPP response kinetics in the PA system suggests the more weakly bound CTEs,\nfacilitating their separation into free charges. This may be attributed to the more\ndelocalized orbitals overlapping of PA system.58,59 This observation is consistent with\nthe shorter charge generation times (  and   ), highlighting the faster CTE\n   \nseparation dynamics in the PA system.\nThroughout the charge generation process, the PA system manifests a gentler energy\nlandscape that facilitates faster exciton diffusion and an energetically ordered interface\npromoting exciton dissociation.6 Our PPP-TAS results also demonstrate faster charge-\ntransfer exciton (CTE) separation rates in PA system relative to SMA system. Besides,\nthe growing population of P-interface assists the exciton dissociation in both systems.\nWe proposed a dual pathway for charge generation originating from E- and P-interface,\nwherein latter may facilitate fast and efficient CTEs separation (Figure 4d).60 The\ndifferent morphologies and charge generation characteristics of the P-interface\nhighlight the distinct electronic properties in the two systems.”\nModified discussion in main text on Page 23:\n“Specifically, In PA system, the more pronounced P-interface, formed by the quasi-\naggregates, constructs a gentle energy landscape that facilitates the efficient charge\ngeneration, while the steeper energy landscape in the SMA system hinders the charge\ngeneration dynamics. We propose that the relative population of E- and P-interface can\nbe estimated by calculating ΔrDoC and   /  .”\n   \nPoint-to-point Response to Referees Letter\nThe comments by the reviewers are in black, our responses are in blue, and the changes\nin the main text and supporting information are tracked in red.\nReviewers’ Comments to Authors:\nReviewer #1 (Remarks to the Author):\nAuthors addressed well. It can be accepted.\nResponse: We thank you so much for your valuable feedback, which improved the\nquality of the manuscript. We are also very grateful for your recognition of our work.\nReviewer #2:\nThe authors have revised the manuscript thoroughly and have addressed all previously\nraised concerns. The manuscript is now in very good shape, and the work is both\ninteresting and valuable. I have a minor comment that, if addressed, will improve clarity\nfor readers.\nResponse: We appreciate your thoughtful comments and suggestions to improve the\nscientific depth of our manuscript. We are also grateful for your positive feedback on\nour work.\n1. Figure S1 is currently misleading. Although the data indicates that the bandgap\nenergy and the CT-state energy are close in value, the Figure shows that CT state energy\nis equivalent to the eVOC,SQ (which is generally 0.25 eV- 0.3 eV lower than the\nbandgap). Fundamentally, these two quantities are different and should not be directly\ncompared. The figure should be revised or clarified to avoid the impression that these\ntwo energies are equivalent or directly comparable in this context.\nResponse: We thank the reviewer for the insightful comments and suggestions. We fully\nagree that our description is misleading. As reviewers mentioned, V is impossible\nOC,SQ\nto compare with CT state energy. We correct Figure S1. We really appreciate the\nreviewer pointing it out.\nCorrected information in SI:\nNote-Figure S1: Energy loss (E ) in the organic photovoltaic, S , ground state; S ,\nloss 0 1\nexcited state; ΔV Shockley-Queisser (SQ) limit-voltage loss; ΔV, radiative\nSQ r\nrecombination voltage loss; ΔV , radiative recombination voltage loss.\nnr\n2. For the TAS data, most of the spectral evolution occurs within the first 2 ps. It would\nbe helpful if the authors could show the laser pulse width —reported as 35 fs in the\nmanuscript, to ensure that the temporal resolution is sufficient to accurately capture\nthese ultrafast dynamics.\nResponse: We thank the reviewer for the insightful comments. We agree that the laser\npulse width for the TAS experiments should be provided to improve data reliability.\nAccordingly, we have measured the pulse width of the pump beam using Frequency-\nResolved Optical Gating (FROG). The measured pulse width is approximately 39 fs,\nwhich is slightly longer than the ~35 fs stated in the Methods section. We attribute this\nslight discrepancy primarily to chirping introduced by optical components such as\nmirrors and lenses. Certainly, We believe that this ~39 fs pulse width provides adequate\ntemporal resolution to ensure the validity of the ultrafast dynamical conclusions drawn\nin our study.\nAdded information in manuscript:\nFigure 4. Charge carrier kinetics and illustrations. (a) Hole transfer kinetics from\nPP-TAS of PA and SMA systems fitting by tri-exponential function, where  present\n \nthe time constant of two interfaces and diffusion-limited transfer, and A are the weight\nn\ncoefficient for each term; (b) The ratio of A and A for two systems. (c) Bound CTEs\n1 2\nseparation kinetics from PPP-TAS at representative EA response wavelength for PA\nand SMA system. (d) Illustration of the dual charge generation pathways originating\nfrom the E-and P-interfaces, highlighting their distinct population ratios and charge\ntransfer time. Grey shaded shape on (a) represents the laser pulse width of transient\nabsorption experiments showing the high time resolution here.\nAdded information in SI:\nFigure S1. a. The 39 fs laser pulse width for transient absorption experiments; b.\nExciton dissociation of two system by extract the kinetics at 810 – 820 nm of TAS\nspectra. The decays are fitted by bi-exponential function with τ and τ . The PA system\n1 1\npossess faster dissociation speed."}, {"round": 2, "reviewer_comments": {"reviewer_1": "Authors addressed well. It can be accepted.", "reviewer_2": "The authors have revised the manuscript thoroughly and have addressed all previously raised concerns. The manuscript is now in very good shape, and the work is both interesting and valuable. I have a minor comment that, if addressed, will improve clarity for readers.\n1. Figure S1 is currently misleading. Although the data indicates that the bandgap energy and the CT-state energy are close in value, the Figure shows that CT state energy is equivalent to the eVOC,SQ (which is generally 0.25 eV- 0.3 eV lower than the bandgap). Fundamentally, these two quantities are different and should not be directly compared. The figure should be revised or clarified to avoid the impression that these two energies are equivalent or directly comparable in this context.\n2. For the TAS data, most of the spectral evolution occurs within the first 2 ps. It would be helpful if the authors could show the laser pulse width —reported as 35 fs in the manuscript, to ensure that the temporal resolution is sufficient to accurately capture these ultrafast dynamics."}, "author_response": "Point-to-point Response to Referees Letter\nThe comments by the reviewers are in black, our responses are in blue, and the changes\nin the main text and supporting information are tracked in red.\nReviewers’ Comments to Authors:\nReviewer #1 (Remarks to the Author):\nAuthors addressed well. It can be accepted.\nResponse: We thank you so much for your valuable feedback, which improved the\nquality of the manuscript. We are also very grateful for your recognition of our work.\nReviewer #2:\nThe authors have revised the manuscript thoroughly and have addressed all previously\nraised concerns. The manuscript is now in very good shape, and the work is both\ninteresting and valuable. I have a minor comment that, if addressed, will improve clarity\nfor readers.\nResponse: We appreciate your thoughtful comments and suggestions to improve the\nscientific depth of our manuscript. We are also grateful for your positive feedback on\nour work.\n1. Figure S1 is currently misleading. Although the data indicates that the bandgap\nenergy and the CT-state energy are close in value, the Figure shows that CT state energy\nis equivalent to the eVOC,SQ (which is generally 0.25 eV- 0.3 eV lower than the\nbandgap). Fundamentally, these two quantities are different and should not be directly\ncompared. The figure should be revised or clarified to avoid the impression that these\ntwo energies are equivalent or directly comparable in this context.\nResponse: We thank the reviewer for the insightful comments and suggestions. We fully\nagree that our description is misleading. As reviewers mentioned, V is impossible\nOC,SQ\nto compare with CT state energy. We correct Figure S1. We really appreciate the\nreviewer pointing it out.\nCorrected information in SI:\nNote-Figure S1: Energy loss (E ) in the organic photovoltaic, S , ground state; S ,\nloss 0 1\nexcited state; ΔV Shockley-Queisser (SQ) limit-voltage loss; ΔV, radiative\nSQ r\nrecombination voltage loss; ΔV , radiative recombination voltage loss.\nnr\n2. For the TAS data, most of the spectral evolution occurs within the first 2 ps. It would\nbe helpful if the authors could show the laser pulse width —reported as 35 fs in the\nmanuscript, to ensure that the temporal resolution is sufficient to accurately capture\nthese ultrafast dynamics.\nResponse: We thank the reviewer for the insightful comments. We agree that the laser\npulse width for the TAS experiments should be provided to improve data reliability.\nAccordingly, we have measured the pulse width of the pump beam using Frequency-\nResolved Optical Gating (FROG). The measured pulse width is approximately 39 fs,\nwhich is slightly longer than the ~35 fs stated in the Methods section. We attribute this\nslight discrepancy primarily to chirping introduced by optical components such as\nmirrors and lenses. Certainly, We believe that this ~39 fs pulse width provides adequate\ntemporal resolution to ensure the validity of the ultrafast dynamical conclusions drawn\nin our study.\nAdded information in manuscript:\nFigure 4. Charge carrier kinetics and illustrations. (a) Hole transfer kinetics from\nPP-TAS of PA and SMA systems fitting by tri-exponential function, where  present\n \nthe time constant of two interfaces and diffusion-limited transfer, and A are the weight\nn\ncoefficient for each term; (b) The ratio of A and A for two systems. (c) Bound CTEs\n1 2\nseparation kinetics from PPP-TAS at representative EA response wavelength for PA\nand SMA system. (d) Illustration of the dual charge generation pathways originating\nfrom the E-and P-interfaces, highlighting their distinct population ratios and charge\ntransfer time. Grey shaded shape on (a) represents the laser pulse width of transient\nabsorption experiments showing the high time resolution here.\nAdded information in SI:\nFigure S1. a. The 39 fs laser pulse width for transient absorption experiments; b.\nExciton dissociation of two system by extract the kinetics at 810 – 820 nm of TAS\nspectra. The decays are fitted by bi-exponential function with τ and τ . The PA system\n1 1\npossess faster dissociation speed."}]

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