Suppressing electron-phonon coupling in perovskite nanoplatelets for efficient pure-red light-emitting diodes with narrow spectral emission

Domain: physics
Published: 2026-04-09
Editorial outcome: major_revision

Abstract
Perovskite light-emitting diodes are promising for next-generation ultrahigh-definition displays, yet efficient pure-red emission (620-650 nm) with high spectral purity remains challenging, with emission linewidths commonly exceeding 30 nm. CsPbI3 nanoplatelets feature the potential for narrow-linewidth emission owing to strong vertical quantum confinement and atomic-level flat surface. Nonetheless, the dynamic motion of native long-chain oleylamine exacerbates lattice vibrations in ultrathin soft lattices, inducing strong electron-phonon coupling and undermining optical advantages. Here, we introduce the rigid 4-(2-aminoethyl)benzenesulfonamide molecule, which partially replaces oleylamine and vertically anchors on the nanoplatelets, sterically restricting the dynamic motion of neighboring oleylamine, thereby mitigating electron-phonon coupling. The resulting light-emitting diodes achieve pure-red electroluminescence at 641 nm with a narrow linewidth of 24 nm, an average external quantum efficiency of 23.2 ± 2.4% (maximum 29.8%), and an operational lifetime of 128.2 h. This work underscores the critical role of electron-phonon coupling modulation in optimizing perovskite optoelectronic devices.

Introduction
Perovskite materials possess tunable bandgaps, high photoluminescence quantum yields (PLQYs), and can be fabricated via low-cost solution processes, making perovskite light-emitting diodes (PeLEDs) promising for advanced display technologies1-11. Although considerable progress has been made in improving external quantum efficiency (EQE)1,6,12, pure-red PeLEDs still face key challenges. These devices are typically based on Br/I mixed-halide perovskites5,13,14, tending to undergo ion migration and phase segregation under device operation15. This instability results in emission redshift and spectral broadening, which hinder the realization of narrow electroluminescence (EL) full width at half maximum (FWHM)16. As a result, their practical use in next-generation display technologies remains limited. Quantum-confined low-dimensional pure-iodide based perovskites offer an effective solution to circumvent the above challenges. Among them, quasi-2D films and small-sized quantum dots are the most widely studied systems4,6,17. However, the rapid nucleation and growth kinetics process hinders size uniformity, causing inhomogeneous emission broadening (FWHM > 30 nm) due to multi-center recombination18,19. By contrast, the perovskite nanoplatelets (NPLs) exhibit distinct structural advantages. The thermodynamic preference against vertical growth in NPLs yields atomically flat basal planes, characterized by uniform thickness20. Given that their emission is primarily determined by strong vertical quantum confinement and is relatively insensitive to lateral size variations, NPLs intrinsically favor narrowband emission20-27.

Despite these merits, pure-red NPLs-based PeLEDs still suffer from broad EL linewidths and unsatisfactory device performances28,29. This limitation primarily stems from the ultrathin geometry of NPLs, which amplifies the inherent lattice softness of perovskites, increasing susceptibility to structural fluctuations20,30-35. Furthermore, the long-chain oleylamine (OLA) ligands, essential for stabilizing the layered structure, introduce significant dynamic disorder due to high conformational freedom, thereby exacerbating lattice vibrations20,36,37 (Fig. 1a). The resulting strong electron-phonon (EP) coupling intensifies non-radiative recombination, promotes carrier scattering, and broadens emission linewidths, ultimately constraining the potential of NPLs for high-performance LEDs30,35,36,38-42.

In this work, we design a rigid-ligand pinning strategy using 4-(2-aminoethyl)benzenesulfonamide (AEBS) (Fig. 1a). The rigid AEBS molecules vertically anchor on NPL surfaces and sterically restrict the dynamic motion of neighboring OLA ligands, thereby mitigating OLA-aggravated EP coupling. This enables high-performance PeLED devices with a maximum EQE and an operational lifetime of 29.8% and 128.2 h, respectively. Our work may inspire the design of NPLs for optoelectronic applications.

Results
Effect of rigid ligand pinning

Density functional theory (DFT) calculations reveal that AEBS adopts a nearly perpendicular configuration on the NPLs surface through strong coordination of sulfonyl (−S(=O)2−) group with Pb2+ ions and −NH2 groups with I- (Fig. 1a, Supplementary Figure 1). The rigid and upright molecular geometry on the NPLs surface sterically restricts the dynamic motion of adjacent OLA ligands (Supplementary Figure 2), effectively reducing ligand-induced lattice vibrations. Molecular dynamics simulations demonstrate the smaller temporal variations in the bond length of Pb−I in AEBS-treated NPLs (AEBS-NPLs, ~2.9-3.2 Å) compared to those without AEBS anchoring (Control-NPLs, ~2.9-3.6 Å) (Fig. 1b), indicating a more stable inorganic [PbI6]4- octahedral framework.

Due to the high polarity of AEBS, direct post-treatment leads to rapid ligand exchange and structural degradation of perovskites, inducing NPLs aggregation and severe photoluminescence (PL) quenching (Supplementary Figure 3). Herein, we pre-load AEBS molecules into mesoporous silica (SBA‑15) as a slow‑release medium (Supplementary Figures 4-7). This controlled delivery retained structural integrity and square platelet morphology of NPLs during post-treatment (Fig. 1c and Supplementary Figures 8-13). As shown in Fig. 1d, AEBS-NPLs exhibit a sharp emission peak centered at 640 nm with a FWHM of ~24 nm, representing the narrowest PL linewidth reported for Pb-based pure-red perovskite to date1,4,6,9,43. The ligand pinning effect of AEBS is further supported by Fourier-transform infrared (FTIR) spectroscopy. The νas(CH2) and νs(CH2) vibrational bands are highly sensitive to the conformational order of hydrocarbon chains. Compared with Control-NPLs, AEBS-NPLs exhibit a marked decrease in the νas(CH2)/νs(CH2) intensity ratio and a pronounced shift of both bands to lower wavenumbers, accompanied by reductions in their fitted bandwidths, indicating enhanced alkyl-chain ordering and suppressed conformational dynamics of the OLA ligand44-46 (Fig. 1e). Oleylammonium iodide (OLAI) and 3-Amino-1-propanesulfonamide (APSA) are introduced to clarify the role of ligand structure. OLAI increases OLA surface coverage and passivates defects without introducing new ligand species, whereas APSA possesses the same head and tail groups as AEBS but lacks a rigid aromatic backbone (Supplementary Figures 14 and 15). The more pronounced alkyl-chain disorder induced by higher OLAI content and the limited conformational constraint of APSA collectively underscore the pinning effect of rigid ligands (Supplementary Figure 16).

Modulation of electron-phonon coupling by ligands

To further elucidate the effect of AEBS ligands on EP coupling in CsPbI3 NPLs, we conduct a comprehensive set of transient and steady-state spectroscopic measurements. Since strong EP coupling accelerates hot carrier cooling and increases energy loss, hot carrier relaxation dynamics serve as a sensitive probe to evaluate EP interactions.47-50. We first examine the early-stage relaxation process via time-resolved PL (TRPL), where the initial rise in TRPL traces reflects the dephasing of initial polarization and the hot carrier relaxation51,52. As shown in Fig. 2a-c and Supplementary Figure 17, the temperature-dependent rise rate (k_rise) of both NPLs follows a power-law dependence k_rise ∝ T^γ (γ > 0). A markedly lower exponent for AEBS-NPLs (γ = 0.89) compared to Control-NPLs (γ = 1.29) is to some extent associated with the weaker EP interaction in AEBS-NPLs41,51 (Fig. 2c). Consistent results are provided by the prolonged rise time of the ground-state bleach (GSB) in transient absorption (TA) spectroscopy, which increases from 0.73 ps in Control-NPLs to 1.43 ps in AEBS-NPLs (Fig. 2d-f and Supplementary Figure 18). Further, the slower hot carrier temperature (Tc) dynamics decay and narrower Raman peaks provide strong evidence for weaker EP interaction in AEBS-NPLs47,48,53-57 (Supplementary Figures 19 and 20). Finally, temperature-dependent steady-state PL measurements provide quantitative evaluation of EP coupling strength. As shown in Fig. 2g-i and Supplementary Figure 21, the dominant PL peak in AEBS-NPLs exhibits a smaller linewidth variation with increasing temperature (from 80 K to 300 K) compared to that in Control-NPLs. Fitting the temperature-dependent linewidth variation reveals that AEBS-NPLs exhibit the lowest exciton-longitudinal optical (LO) phonon coupling strength (Γ_LO) of 36.6 meV (Fig. 2i and Supplementary Figure 22).The markedly lower Γ_LO in AEBS-NPLs indicates that AEBS modification effectively suppresses EP coupling, accounting for the narrow emission linewidth of the AEBS-NPLs30,54,58 (Fig. 1d), in agreement with the reduced Huang-Rhys factor (S) (Supplementary Figure 23).

Enhanced optoelectronic properties

EP coupling in CsPbI3 NPLs plays a critical role in governing their electrical and optical behavior. Space-charge-limited current (SCLC) measurements reveal that both electron and hole mobilities are markedly increased in AEBS-treated NPLs compared to Control-NPLs (Fig. 3a,b and Supplementary Figure 24). Consistently, the electrical conductivity (σ) of AEBS-NPLs film reaches 9.42 × 10-6 S m-1, 2.2-fold higher than that of Control-NPLs (4.25 × 10-6 S m-1) (Fig. 3c). These improvements are primarily attributed to suppressed carrier scattering due to weakened EP coupling, further assisted by the structural advantages of the short-chain conjugated AEBS ligands and defect passivation30,35,38,59 (Supplementary Figure 25 and Supplementary Table 1). Moreover, optical characterizations further underscore the benefits of EP coupling suppression. As shown in Figs. 2g,h and 3d, the weakened EP coupling in AEBS-NPLs suppresses exciton dissociation, thereby achieving a high exciton binding energy (Eb) and effectively preventing thermal degradation60,61. In addition, the combination of AEBS passivation and weakened EP coupling effectively reduces non-radiative recombination (Fig. 3e and Supplementary Tables 1 and 2), leading to an overall improvement in PLQYs51,55,58,62 (Fig. 3f). These combined effects endow AEBS-NPLs with superior structural and photophysical robustness under diverse operational and environmental conditions (Fig. 3g and Supplementary Figures 26-29).

Electroluminescence performance and operational stability

Encouraged by the enhanced optoelectronic properties, we further fabricate PeLEDs with a multi-layer structure of ITO/PEDOT:PSS/PTAA/NPLs/TPBi/LiF/Al (Fig. 4a and Supplementary Figures 30 and 31). The AEBS-NPLs based PeLEDs deliver voltage-invariant EL spectra centered at ~641 nm, featuring the narrowest EL linewidth of ~24 nm among all the reported Pb-based pure-red PeLEDs (Fig. 4b, Supplementary Figure 32 and Supplementary Table 3). The corresponding Commission Internationale de l’Eclairage (CIE) chromaticity coordinates of (0.702, 0.296) satisfy the Rec.2020 standard, outperforming the control device (Supplementary Figure 33). Angle-dependent EL intensity follows a Lambertian profile (Fig. 4c). The current density-voltage-luminance (J-V-L) and EQE-J characteristics of a representative AEBS-NPLs based PeLED demonstrate a maximum EQE of 23.7% and a maximum luminance (L_max) of 2,060 cd m-2. In contrast, the control device achieves a significantly lower EQE of 9.5% and L_max of 550 cd m-2 (Fig. 4d,e). AEBS-NPLs based PeLEDs exhibit suppressed efficiency roll-off, arising from weakened EP coupling that mitigates exciton dissociation induced quenching and improved energy-level alignment that promotes balanced charge injection and suppresses Auger recombination7,60,61 (Fig. 3d and Supplementary Figure 30). Statistical analysis of 30 devices reveals a distribution of EQE ranging from 19.3% to 29.8% for AEBS-NPLs based PeLEDs, with an average of 23.2 ± 2.4% (Supplementary Figures 34-36). In comparison, PeLEDs based on OLAI-NPLs and APSA-NPLs achieve limited EQE enhancement (Supplementary Figure 37). A summary of reported EQEs and EL linewidths for pure-red PeLEDs is provided in Figure 4f and Supplementary Table 3. The operational stability of the devices is further evaluated. Under continuous operation at an initial luminance of ~100 cd m-2, the AEBS-NPLs based device achieves a half-lifetime (T50) of ~128.2 h, ~15-fold longer than the control device (Fig 4g and Supplementary Figure 38). This represents one of the longest operational lifetimes reported for pure-red PeLEDs (Supplementary Table 3). We further investigate the charge dynamics and thermal behavior of the devices to understand the origin of the improved device performance. Transient EL (Tr-EL) reveals that AEBS-NPLs based devices exhibit shorter EL rise times (tr) and fall times (tf) than the control counterparts (Fig. 4h and Supplementary Table 4), indicative of more efficient carrier injection and radiative recombination4,58. These findings are consistent with the higher current density observed at identical biases and the lower turn-on voltage in these devices11 (Fig. 4d). Moreover, thermal imaging reveals that the AEBS-NPLs based device undergoes significantly less Joule heating as voltage increases to 5 V, exhibiting a surface temperature rise of only 5.6 °C, in contrast to 13.9 °C observed in the control device (Supplementary Figure 39). The reduction in Joule heating originates from mitigated EP coupling and improved energy-level alignment, promoting efficient charge injection and transport while reducing series resistance and nonradiative losses. Reduced Joule heating, the elevated ion-migration activation energy, and the stable lattice enabled by AEBS ligand pinning together lead to a marked improvement in the stability of AEBS-NPLs based devices (Fig. 1b and Supplementary Figures 39 and 40).

Methods
Materials

Cesium carbonate (Cs2CO3, 99.9%) and chlorobenzene (C6H5Cl, 99.9%) were purchased from Alfa Aesar. Lead(II) acetate trihydrate (Pb(OAc)2·3H2O, 99.99%), oleylamine (OLA, 80-90%), oleic acid (OA, 90%), ethyl acetate (99.8%), isopropyl alcohol (99.9%), 1-octadecene (ODE, 90%) and 4-(2-aminoethyl)benzenesulfonamide (AEBS) were purchased from Aladdin. Zinc iodide (ZnI2, 99.99%) and n-hexane (99%) were purchased from Shanghai Macklin Biochemical Co., Ltd. The mesoporous particles (SBA-15) were purchased from Nanjing XFNANO Co. Ltd. 1,3,5-Tris(1-phenyl-1H-benzimidazol-2-yl)benzene (TPBi) and lithium fluoride (LiF) were purchased from Luminescence Technology Corp. Poly(ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS; Heraeus-Clevios PVP AI4083) and poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA) were purchased from Xian Yuri Solar Co, Ltd. All chemicals were used directly without any further purification.

Preparation of precursor

Cs2CO3 (0.21 g), Pb(OAc)2·3H2O (0.475 g), OA (2.5 mL) and ODE (10 mL) were loaded into a 50 mL three-necked flask, and the mixture was degassed for 15 min at 100 °C under argon. Subsequently, the mixture was heated at 120 °C under argon atmosphere for 30 minutes until a transparent solution was obtained. The resulting precursor solution was heated at 100 °C under argon before injection.

Preparation of molecule loaded mesoporous silica

To synthesize the nanocomposite, 50 mg of AEBS powder was dissolved in 10 mL of isopropanol, and the SBA-15 was impregnated with the solution, followed by ultrasonication to facilitate the infiltration of the solution into the mesopores. The solid product was then separated, washed three times with isopropanol, and vacuum-dried to obtain the final material.

Synthesis and purification of nanoplatelets

For the typical synthesis of CsPbI3 NPLs, 0.26 g ZnI2, 2.3 mL OA, 1.8 mL OLA and 6 mL ODE were loaded into a 50 mL three-neck flask, which was degassed and dried under vacuum for 30 min at 120 °C. Then the temperature was reduced to 100 °C and 1.5 mL precursor solution was quickly injected. After waiting for 1 min, the reaction mixture was immediately cooled down to room temperature by an ice-water bath.

The crude solution was transferred to a 50 mL centrifuge tube, and 15 mL of ethyl acetate was added. The mixture was centrifuged at 9,800 × g for 5 min, and the supernatant was discarded. The precipitate was dissolved in 1 mL of n-hexane, followed by the addition of 3 mL of ethyl acetate. The resulting mixture was centrifuged at 9,800 × g for 5 min, and the precipitate was collected. The precipitate was dissolved in 1 mL of hexane and centrifuged at 2,460 × g for 3 min to retain the supernatant. Ethyl acetate (3 mL) was added to the supernatant, and the mixtures were centrifuged at 9,800 × g for 5 min to isolate the precipitates. Finally, the precipitates were redispersed in n-hexane. AEBS-functionalized NPLs were prepared by ultrasonicating a dispersion of NPLs in n-hexane containing AEBS/SBA-15 (~5 mg). A sonication time of ~3 min was employed to achieve the desired surface AEBS-to-OLA ratio (Supplementary Figure 7). The final product was collected from the supernatant after centrifugation at 9,800 × g for 1 min. For OLAI- and APSA-modified NPLs, the ligand was added to the NPL dispersion in n-hexane, stirred for ~20 min, and centrifuged at 9,800 × g for 1 min to collect the supernatant. All n-hexane solutions containing NPLs are filtered through 0.22 μm PTFE filters. The resulting NPLs solutions were stored for further characterization and LED fabrication.

Device fabrication

PeLEDs were fabricated on ITO-coated glass substrates with a sheet resistance of ~17 Ω sq-1. Before using, these coated substrates were cleaned with deionized water, acetone, and isopropanol for 15 min, respectively. Then these substrates were treated with oxygen plasma for 15 min. A PEDOT:PSS solution was spin-coated onto the ITO substrate at 4,000 rpm for 40 s and then baked at 150 °C for 20 min in ambient air. Subsequently, the ITO substrate was transferred into a nitrogen-filled glovebox. PTAA (8 mg mL-1 in chlorobenzene) was spin-coated onto PEDOT:PSS layer at 4,000 rpm for 40 s, followed by annealing at 120 °C for 20 min. Perovskite was spin-coated at 2,000 rpm for 40 s. After that, TPBi (40-50 nm), LiF (1 nm) and an Al electrode (100 nm) were thermally evaporated with a vacuum pressure below 4 × 10-4 Pa.

Material characterizations

High-resolution transmission electron microscope (HRTEM) images and HAADF-STEM images were obtained by Themis Z microscope, and the accelerating voltage was 200 kV. AFM images of NPL films were measured by a Dimension Icon instrument. XRD patterns of perovskite films were obtained using a MiniFlex 600 X-ray diffractometer with a Cu-Kα source (λ = 1.54056 Å). The FTIR spectra of NPLs were measured by an IRTracer-100 Fourier infrared spectrometer. 1H nuclear magnetic resonance (1H NMR) measurements were recorded on a Bruker AVANCE NEO 400 spectrometer. Thermogravimetric analysis (TGA) was carried out using a NETZSCH STA 449 F3 instrument. The samples were heated from 30 °C to 800 °C at a rate of 20 °C·min-1 under a nitrogen flow. Grazing incidence small-angle X-ray scattering (GISAXS) data were collected using an X-ray wavelength of 0.154 nm. XPS and UPS were measured by a spectrometer system (Nexsa G2, Thermo Fisher Scientific). A monochromatic Al Kα line (1,486.6 eV) was used for XPS, and He I radiation (21.2 eV) was used for UPS. The conductivity of a film was measured by a semiconductor parameter analyzer (Keithley, 4200) with a probe station. A 100 nm-thick Au layer was deposited onto a glass/perovskite film by thermal evaporation. Field-effect transistor (FET) exhibits a channel length of 50 μm and a channel width of 1 cm. The thickness of the perovskite film is 30 nm.

Optical characterizations

UV-visible absorption spectra were acquired using a Lambda 1050+ spectrophotometer. The Raman spectra were obtained using a Horiba LabRAMP HR Evolution confocal Raman microscope. A 785 nm laser was used as the excitation source. The PLQY values were measured using a system that included a xenon flash lamp, a QE Pro spectrometer and a custom-built integrating sphere. Temperature-dependent steady-state PL spectra were recorded using a confocal microscope (Witec Alpha300R) equipped with a liquid-nitrogen-cooled cryostat, with a 405 nm laser as the excitation source.

TRPL measurements were conducted with the confocal microscope coupled to a streak camera (C10910, Hamamatsu). A Ti: Sapphire pulsed laser operating at 400 nm (pulse width: 80 fs; repetition rate: 80 MHz) was employed as the excitation source.

Time-resolved TA spectra were acquired using femtosecond broadband pump-probe microscopy. The light source was a regenerative amplifier system (Spitfire-ace, Spectra-Physics) operating at 800 nm with a pulse width of 80 fs and a repetition rate of 250 Hz. The output from the amplifier was divided into two paths; one was frequency-doubled to produce a 400 nm pump beam. The other beam was focused into a sapphire plate (C-cut, 2 mm thick) to form the continuous white light with a range of 450-750 nm as the probe beam. Both beams were directed into a custom-built microscope and focused onto the samples. The sub-picosecond time delay between the pump and probe pulses was controlled using a mechanical delay line (Newport, M-ILS250CC, 250 mm). A spectrometer (Avantes, AvaSpec-2048L) positioned after the microscope was used to capture the transient signals. All measurements were performed under comparable experimental conditions.

Device characterizations

The active area of the device was defined as 4 mm2. Electroluminescence characterization was performed at room temperature in a nitrogen-filled glovebox using a Keithley 2400 source meter coupled with an integrating sphere (50 mm diameter, Shenzhen Pynect) and an Ocean Optics QE Pro spectrometer. The angular dependence of the emission intensity was collected using a Konica Minolta CS-200 detector. The operational lifetimes of PeLEDs were evaluated via a commercial organic LED aging system (ZJZCL-1) in a nitrogen environment. Thermal images of the samples were acquired using a Fluke Ti401 PRO camera. The Tr-EL signal was collected by a high-speed photomultiplier tube (Hamamatsu, H10721-20) and transformed into a current signal. The current signal was sent to a transimpedance amplifier (Femto, DHPCA-100) and then collected by a digital oscilloscope (MXR108B).

The ion-migration activation energy was measured using a FET device architecture. A 10 V bias was applied to the electrodes for ~20 s with a source meter (Keithley 2400) to induce ion migration. Upon abrupt voltage removal, a negative current arising from ion-vacancy redistribution was recorded and decayed exponentially, with its decay reflecting the ionic transport dynamics. Measurements were conducted from 220 to 310 K using a liquid-nitrogen-cooled cryostat. The transient currents were fitted with a double-exponential function, and the slower decay constant (τ), corresponding to the ion redistribution recovery time, was used to extract the activation energy.

Optical simulation

Both random orientation (isotropic dipole distribution) and fully face-down orientation of emitters are assumed in this model. The following optical channels are considered in the simulation: nonradiative mode, surface plasmon polariton (SPP) mode, waveguide mode, absorption mode, substrate mode, and air mode. The air mode corresponds to the theoretically simulated EQE limit.

Density functional theory calculation

In this work, the calculations are conducted within the framework of DFT using Vienna Ab Simulation Package (VASP)63,64. The generalized gradient approximation exchange-correlation function is described by Perdew-Burke-Ernzerhof (PBE), and the projector augmented wave pseudopotential is introduced with a cutoff of 400 eV (Ref.65). The models are relaxed until the force convergence criterion is less than 0.01 eV Å-1 per atom and the energy convergence criterion is less than 10-5 eV. To avoid the interaction between the two nearest neighbor unit cells, the vacuum is set to 20 Å in the Z-direction. A 4 × 4 × 1 r-centered k-point mesh is used for Brillouin-zone sampling.

Temperature-dependent photoluminescence line fitting

The FWHM of the dominant peak in each temperature-dependent PL spectrum is extracted by deconvoluting the PL spectra and plotted against temperature according to the following equation, enabling the estimation of the EP coupling strength58:

Γ(T)= Γ_inh + Γ_ac T + Γ_LO / (exp(E_LO / (kB T)) − 1) (1)

in which Γ_inh represents the inhomogeneous broadening arising from variation of crystal size, shape, and composition, as well as the scattering process associated with the imperfections of the lattice, Γ_ac is the exciton-acoustic phonon coupling coefficient, Γ_LO denotes the exciton-LO phonon coupling strength, E_LO represents the LO phonon energy and kB is the Boltzmann constant. The two mechanisms of acoustic phonon deformation scattering and Fröhlich interaction with LO phonon are generally responsible for the emergence of EP coupling. In the low-temperature regime (< 110 K), the EP interaction is predominantly governed by acoustic phonons, while high-energy LO phonons dominate this interaction in the high-temperature region. Therefore, the fitting above 110 K mainly considers the Γ_inh and Γ_LO terms, with E_LO constrained within the Raman-determined range to ensure more rigorous and reliable quantification38,39.

Exciton binding energy calculation

The exciton binding energy is determined by fitting the temperature-dependent integrated PL intensities of the dominant emission peak using the Arrhenius equation6:

I(T) = I0 / (1 + A exp(−Eb / (kB T))) (2)

where I0 is the integrated PL intensity at 0 K, Eb is the exciton binding energy, and A is the coefficient.

Carrier mobility calculation

To evaluate the out-of-plane carrier mobility of CsPbI3 NPLs, SCLC measurements are systematically conducted on both EODs and hole-only devices (HODs). The J-V curves of the fabricated devices can be divided into three regions based on the voltage‑dependent slope (k): an ohmic region (k = 1) in the low‑injection regime, a trap‑filled limit (TFL) region (k > 3), and an SCLC region (k = 2). Carrier mobility for each device is calculated from the Mott-Gurney law in the Child regime of trap-free SCLC transport7, as follows:

J = 9/8 εr ε0 μ (V^2 / d^3) (3)

where V is the applied voltage, d is the thickness of film, εr is the relative permittivity of perovskite (6.32 for CsPbI3), ε0 is the vacuum permittivity, and μ is the carrier mobility.

Defect density calculation

The trap-filled limit voltages of HODs and EODs are extracted and combined with the following equation to calculate the total trap state density of the perovskite films6,7:

nt = 2 εr ε0 VTFL / (e d^2) (4)

where nt is the trap state density, VTFL is the trap-filled limit voltage, and e is the elementary charge, respectively.

Conductivity calculation

The σ is calculated using the following equation5,66:

σ = (I / V) × (l / (D × W)) (5)

where l is the channel length, D is the thickness of the film, W is the channel width and I/V is the slope of the current-voltage curve.

Peer review rounds
[{"round": 1, "reviewer_comments": {"reviewer_1": "The dynamic motion of long-chain oleylamine (OLA) ligands leads to strong electron-phonon coupling (EPC) in CsPbI3\nNPLs, which deteriorates their electrical and optical properties. In this manuscript, the authors report that, by incorporating\nthe rigid molecular AEBS, the lattice vibrations and EPC are significantly suppressed. The resulting perovskite light-emitting\ndiodes (PeLEDs) achieve a maximum EQE of 29.8% and a record-narrow emission linewidth of 24 nm. The authors\nsystematically investigate the impact of the AEBS ligand on structural properties, EPC, and electroluminescence\nperformance. However, several points remain unclear and require clarification.\n1. The manuscript describes replacing OLA ligands with AEBS. Could the authors clarify how the replacement process is\ncontrolled besides the employment of silica? Specifically, is the amount of AEBS incorporated tunable, and how is the ratio\nof remaining OLA ligands monitored or adjusted? This information is important because the relative composition of AEBS\nand OLA on the NPL surface could significantly influence the optoelectronic properties.\n2. In addition, the chemical interactions between the perovskite surface and AEBS need to be clarified. Considering the\nmultiple functional groups in AEBS and their potential impact on surface defects, experimental evidence should be provided\nto demonstrate the specific chemical interaction at the perovskite-ligand interface.\n3. The decreased νas(CH₂)/νs(CH₂) intensity ratio and red shift of both bands suggest enhanced ligand ordering on the NPL\nsurface. In addition to intensity changes and peak shifts, is there any observation of peak narrowing for these bands?\n4. In AEBS-NPLs, weakened EPC suppresses exciton dissociation and increases exciton binding energy. This should\nreduce the PL lifetimes and the average lifetimes when exciton recombination dominates. The authors should clarify this\npoint.\n5. The PL images in Figure 3g show that the degradation of the control sample is not uniform. Please provide an explanation\nfor this nonuniformity.\n6. The manuscript states that both Joule heating and electric-field-induced degradation are significantly suppressed. Could\nthe authors elaborate on the mechanism behind this suppression?\n7. Although improved injection efficiency may contribute to a reduced turn-on voltage, it is unclear from Figure 4d what\nprimarily accounts for the observed decrease of 0.2–0.3 V. The authors should clarify this point.", "reviewer_2": "This manuscript reports a strategy to suppress electron-phonon (EP) coupling in CsPbI₃ nanoplatelets (NPLs) using a rigid\nligand (AEBS) to achieve efficient pure-red light-emitting diodes (PeLEDs) with a narrow emission linewidth of 24 nm. While\nthe study addresses an important topic in perovskite optoelectronics and presents an interesting ligand-pinning concept, the\nmanuscript suffers from several critical issues that undermine the validity of its central claims and the robustness of its\nconclusions. The evidence provided is insufficient to convincingly demonstrate that the observed improvement is primarily\ndue to the inhibition of EP coupling. Therefore, the manuscript in its current form is not recommended for publication. Below\nare specific major concerns that must be adequately addressed:\n1. The manuscript heavily relies on the claim that AEBS treatment suppresses EP coupling, but the evidence is indirect. Key\nparameters for quantifying EP coupling, such as the Huang-Rhys factor or direct measurement of phonon modes via ultrafast\nspectroscopy, are not provided.\n2. The authors claim AEBS vertically pins on the CsPbI₃ NPL surface. However, there is a lack of direct structural evidence.\nHow can the proposed perpendicular configuration be conclusively verified? Meanwhile, the proposed mechanism where\nAEBS \"pins\" dynamic OLA ligands is speculative. No direct experimental evidence is provided.\n3. How can the authors rule out that the observed effects are not simply due to superior surface passivation by AEBS,\nrather than the proposed \"pinning\" of OLA ligands? The study lacks a control experiment using a structurally similar but flexible\nligand to isolate the effect of ligand rigidity from other chemical properties.\n4. The reported maximum EQE of 29.8% is an outlier in the statistical distribution (19.3% to 29.8%), and the average EQE is\n23.2 ± 2.4%. The large standard deviation suggests significant device-to-device variation, raising a concern about the\nreproducibility and the representativeness of the champion device.\n5. The improved device performance is primarily attributed to suppressed EP coupling. However, other factors—such as\nenhanced surface passivation, improved energy level alignment, or reduced defect density—could also or more significantly\ncontribute to these improvements. How can the authors deconvolve the contribution of suppressed EP coupling from other\nbeneficial effects of AEBS treatment?\n6. The interpretation of hot-carrier cooling based on TRPL and TA is indirect. The rise times in TRPL are influenced by\nmultiple factors, such as trap-assisted processes or dielectric screening, not solely EP coupling.\n7. The SCLC measurements show that the mobility in AEBS-NPLs increased, but the analysis did not distinguish between\nthe decrease of EP coupling and other factors, such as the improved film morphology or the reduced trap density.", "reviewer_3": "I co-reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co-review manuscripts.", "reviewer_4": "The manuscript presents a clear and compelling strategy to suppress electron–phonon (EP) coupling in CsPbI₃\nnanoplatelets (NPLs), which has long been a critical bottleneck limiting the spectral purity and device performance of pure-\nred PeLEDs. The introduction of a rigid ligand—4-(2-aminoethyl)benzenesulfonamide (AEBS)—as a “rigid-ligand pinning”\nmotif is conceptually strong and addresses the fundamental issue of lattice softness and dynamic disorder originating from\nlong-chain oleylamine ligands. The authors convincingly demonstrate that AEBS anchoring suppresses lattice vibrations,\nreduces EP coupling strength, and narrows both PL and EL linewidths.\nImportantly, the achieved device metrics—an EL FWHM of 24 nm, a peak EQE of up to 29.8%, and an operational T₅₀ of\n128.2 h—are among the best reported for pure-red PeLEDs and highlight the technological relevance of the approach. The\nmanuscript further benefits from a broad and well-integrated set of spectroscopic analyses (TRPL, TA, temperature-\ndependent PL, Raman), providing multi-angle evidence for weakened EP interactions. Overall, the work represents a\nsignificant and timely contribution to advancing perovskite NPL-based optoelectronics.\nWhile this work has many merits, we believe that several fundamental issues require further clarification and supporting\nevidence.\nRegarding these points, I comment on points below.\n<Lack of quantitative evaluation of AEBS incorporation>\nAlthough FTIR and XPS analyses confirm AEBS adsorption, the manuscript does not offer quantitative information regarding\nthe extent of ligand exchange. The relative proportions of AEBS and native OLA ligands remain unclear.\nTo substantiate the mechanistic claims, quantitative measurements (e.g., TGA, quantitative NMR, or XPS ratio analysis)\nshould be provided to determine the ligand coverage and the AEBS/OLA ratio.\n<Generalizability and mechanistic clarity of the SBA-15 assisted slow-release method>\nThe use of SBA-15 as a slow-release matrix to mitigate structural degradation during AEBS treatment is intriguing, but its\ngenerality remains ambiguous. It is unclear whether this approach applies to other highly polar or rigid ligands.\nAdditionally, evidence for the AEBS release kinetics from SBA-15 is absent. Providing adsorption/desorption profiles or\nrelease-time dependence would greatly strengthen the methodological section.\n<Insufficient discussion of broader electronic and interfacial effects>\nBeyond EP coupling suppression, AEBS—owing to its strong polarity and rigid structure—may influence trap densities,\nsurface dipoles, and ion migration. UPS data suggest modifications to energy alignment, yet the manuscript does not fully\nexplore the broader electronic implications.\nA more detailed analysis separating EP-related effects from defect passivation and ion-transport effects would provide a\nmore complete and accurate interpretation of the results.\n<Limited insights into device degradation pathways>\nWhile the reported operational stability is excellent, the manuscript provides little mechanistic insight into degradation\nprocesses.\nAnalyses such as EL spectral evolution under bias, voltage rise during operation, or ion migration–related signatures would\nhelp clarify the origin of the improved device lifetime and reinforce the claims of structural stabilization.\n<Oversimplified attribution of emission broadening in the control NPLs>\nThe authors attribute the broader emission linewidth of the control sample primarily to enhanced EP coupling. However,\nother factors, including trap-mediated recombination, surface reconstruction, and OLA desorption, are also likely\ncontributors, particularly in light of the stability data presented in the SI.\nA more nuanced discussion acknowledging these additional mechanisms is recommended.\nI think, the manuscript presents impactful results and a highly interesting mechanistic strategy. However, the issues raised\nabove, particularly regarding ligand quantification, method generalizability, and degradation analysis, must be satisfactorily\naddressed to solidify the mechanistic claims and the robustness of the conclusions.", "reviewer_5": "Hua et al. developed a rigid-ligand pinning strategy by partially substituting native OLA ligands with 4-(2-\naminoethyl)benzenesulfonamide (AEBS) ligands via post treatment. The AEBS ligand substitution leads to a more ordered\nsurface with lower exciton-phonon coupling and high photoluminescent quantum efficiency. Based on the AEBS treated\nNPLs, the authors can fabricated record efficiency for NPL LED devices with average EQE of 23.2% (best pixel EQE 29.8%)\nand an operational lifetime of 128.2h at 100 cd m-2. The work is well written and supported by adequate experimental\nevidence to support their claim. I would suggest it to be published in Nat. Commun. after the following points being\naddressed.\n1. The authors perform fs-TA spectroscopy to investigate early kinetics of the hot carrier cooling as indirect evidence of\ncarrier-phonon coupling. The faster cooling of the controlled NPLs may also influence by surface traps as the early time hot\ncarrier cooling can also be governed by direct trapping process of the hot carriers. Could the author elaborate how to de-\ncouple the factors from hot carrier trapping and electron phonon coupling to the influence of the early cooling kinetics.\nI would suggest to include a fluence dependent TA study to see if the cooling kinetic changes upon different excitation\nfluence. If the cooling time difference is caused by trap, it would be mediated at when increasing from low to high excitation\npower due to trap filling. At the meantime, since Frohlich coupling at sub ps time scale is intrinsic material properties, it\nwould be not influence by pump fluence.\n2. Since the AEBS also simultaneously passivate surface traps, it would be nice to isolate the effect of trap passivation to\nsurface reordering in terms of explaining electron-phonon coupling strength obtained from cryo-PL measurement. The\npresence of surface trap may also introduce extra phonon modes in the lattice which affect the coupling strength, would it\npossible to compare a sample with extra OLAm or OA ligands passivation, so we reduce the surface traps but keep the\nsurface more disordered so that we can compare the effect only due to AEBS pinning effect.\n3. Figure 2g shows the PL shifted to a higher energy when increasing from cryo temperature to room temperature. In\ncontrast, the treated sample in Fig.2h, show a blue shift then red shift from below 100K to 300 K. Could the author elaborate\nthe reasons? Does it to do with ligand reconstructions? With AEBS ligands, after certain temperature is reached, it thermally\nactives the ligands which triggering stronger interactions with neighbouring nanoplatelets that leads to more delocalized\ncarriers that gives lower energy emission?\n4. In Fig.S13, the Pb-I stretching modes gets restricted after AEBS treatment as the peak at 108 cm-1 gets narrower. Is there\na reason that this mode is being selectively constrained? The I-Pb-I at 55 cm-1 seems not being affected as the peak width\nstays more or less constant.\n5. Does the Raman peak intensity at 232 cm-1 for PbI2 formation changed overtime during the measurement, or this is\ncoming from pre-exist PbI2 on the surface.\n6. For PeLEDs, typical outcoupling efficiency is around 20-25% for Lambertian emission. Fig4c shows there are marginal\ndifference in emission profile, is there a certain device structure or photonic structures in the device, such as face-down\nalignment of NPls that can leads to potential higher outcoupling for the maximum efficiency of 29.8%? Has the authors done\nany optical simulations in their device to check the thermotical efficiency limit?\n7. Additionally, Figure S23 demonstrated the performance matrix for the best device, but the current density and maximum\nluminance of the best device is much lower than the average device after treatment and the controlled device shown in Main\nFigure 4d. Is there a specific reason?"}, "author_response": "Response to the comments from Reviewer #1\nThe dynamic motion of long-chain oleylamine (OLA) ligands leads to strong electron-\nphonon coupling (EPC) in CsPbI NPLs, which deteriorates their electrical and optical\n3\nproperties. In this manuscript, the authors report that, by incorporating\nthe rigid molecular AEBS, the lattice vibrations and EPC are significantly suppressed. The\nresulting perovskite light-emitting diodes (PeLEDs) achieve a maximum EQE of 29.8%\nand a record-narrow emission linewidth of 24 nm. The authors systematically\ninvestigate the impact of the AEBS ligand on structural properties, EPC, and\nelectroluminescence performance. However, several points remain unclear and require\nclarification.\nReply：\nWe sincerely thank the reviewer for a thorough evaluation of our manuscript and\nfor providing valuable comments. We have carefully revised the manuscript in\naccordance with the reviewer’s suggestions and provide point-by-point responses below.\nQ1. The manuscript describes replacing OLA ligands with AEBS. Could the authors\nclarify how the replacement process is controlled besides the employment of silica?\nSpecifically, is the amount of AEBS incorporated tunable, and how is the ratio of\nremaining OLA ligands monitored or adjusted? This information is important because\nthe relative composition of AEBS and OLA on the NPL surface could significantly\ninfluence the optoelectronic properties.\nReply：\nWe appreciate the reviewer’s insightful comment. The amount of AEBS ligands\nanchored on the NPL surface can be regulated by varying the post-treatment time. As\nshown in Fig. R1a,b, the optical properties of NPLs exhibit a clear time-dependent\nevolution. The PL linewidth reaches a minimum at approximately 3 min. Excessive\nexposure to the polar AEBS environment causes a decline in PL intensity and linewidth\nbroadening, likely due to ligand-induced surface reconstruction or NPL sintering\n(Supplementary Fig. 3). Consequently, we employed the optimized 3 min treatment to\nprepare the AEBS-NPLs in this manuscript.\nTo determine the OLA/AEBS ratio and total ligand density on AEBS-NPLs, we\nemployed a combination of 1H nuclear magnetic resonance (1H NMR) spectroscopy\nand thermogravimetric analysis (TGA) (Fig. R1c,d) (J. Am. Chem. Soc., 2024, 146,\n29104; Angew. Chem. Int. Ed., 2022, 61, e202111443). The specific details are as\nfollows:\nThe ligand density (D ), defined as the number of ligands per unit surface area of\nL\nthe NPLs, can be calculated as follows:\n(m /M )N\nD  L L A\nL (m A )/( V )\nNPL NPL NPL NPL\nwhere m is the total mass of the ligands, M is the relative molecular mass of the\nL L\ncorresponding ligand, N is Avogadro constant, m is the mass of ligand-free NPLs,\nA NPL\nρ is the density of CsPbI NPLs (4.84 g cm-3), V is the volume of a single NPL,\nNPL 3 NPL\nand A is the surface area of a single NPL. TGA yields m of 2.515 mg and 2.912\nNPL NPL\nmg and m of 0.300 mg and 0.338 mg for the Control-NPLs and AEBS-NPLs,\nL\nrespectively. Together with the 1H NMR determined OLA to AEBS molar ratio of\napproximately 1:0.12 and the NPL dimensions, the surface ligand densities are\ncalculated to be ~1.45 and 1.50 nm-2 for the Control-NPLs and AEBS-NPLs,\nrespectively.\nThe relevant data have been added to the Supplementary Information (Supplementary\nFigs. 7 and 13), and the manuscript has been revised accordingly.\nFig. R1 (Supplementary Fig. 7 and 13). a, PL spectra of NPLs after post-treatment with\nAEBS/SBA-15 for different durations. b, Evolution of the PL FWHM extracted from (a)\nas a function of post-treatment time. c,d, TGA curves (c)1H NMR spectra (d) of both\nNPLs.\nQ2. In addition, the chemical interactions between the perovskite surface and AEBS\nneed to be clarified. Considering the multiple functional groups in AEBS and their\npotential impact on surface defects, experimental evidence should be provided to\ndemonstrate the specific chemical interaction at the perovskite-ligand interface.\nReply:\nThank you for your comment. We previously provided a brief discussion of the\ninteraction between AEBS and the CsPbI NPL surface in the captions of\nsection to provide a more detailed analysis.\nCompared to pure AEBS, the characteristic S=O stretching vibration (1154 cm-1)\nin AEBS-NPLs is broadened and slightly shifted toward lower wavenumbers,\nindicating coordination between the (−S(=O) −NH ) group and the NPL surface4-6 (Fig.\n2 2\nR2a). Characteristic S 2p orbital peaks and an additional peak at 399.3 eV (assigned to\nthe −NH group) in AEBS-NPLs further confirm the presence of AEBS ligands5,7 (Fig.\nenergies for the AEBS-NPLs, which is attributed to the electron-withdrawing nature of\nthe sulfonamide group upon coordination with surface Pb2+ ions (Fig. R2c). This\ncoordination-induced electron withdrawal leads to a redistribution of electron density\naround the Pb centers7,8. Meanwhile, the I 3d peaks of AEBS-NPLs also shift toward\nhigher binding energies (Fig. R2d), which can be attributed to the reconstruction of the\nsurface electronic environment caused by strong ligand-surface interactions and defect\npassivation. Hydrogen-bonding interactions between the −NH groups and surface I⁻\n2\nfurther contribute to the modulation of the local electrostatic environment. These\nexperimental observations support the DFT-predicted head-end binding configuration\nof AEBS on the NPL surface (Supplementary Fig. 1).\nThe relevant information has been incorporated into the caption of Supplementary Fig.\n12 in the Supplementary Information.\nReferences\n4: Adv. Mater., 2024, 36, 2400347. 5: ACS Energy Lett., 2024, 9, 1125. 6: Nature 2023,\n615, 830. 7: Adv. Mater., 2023, 35, 2209002. 8: Adv. Mater., 2023, 35, 2303938.\nFig. R2 (Supplementary Fig. 12). Surface analysis of Control-NPLs and AEBS-NPLs.\na, FTIR spectra of Control-NPLs, AEBS-NPLs and AEBS. b-f, High resolution X-ray\nphotoelectron spectroscopy (XPS) spectra of elements from both samples: Cs 3d (b), Pb\n4f (c), I 3d (d), N 1s (e) and S 2p (f).\nQ3. The decreased ν (CH )/ν (CH ) intensity ratio and red shift of both bands suggest\nas 2 s 2\nenhanced ligand ordering on the NPL surface. In addition to intensity changes and peak\nshifts, is there any observation of peak narrowing for these bands?\nReply:\nThe FWHMs of the ν (CH ) and ν (CH ) vibrational bands of the alkyl chains\nas 2 s 2\ndecrease by 0.70 and 0.67 cm-1 after AEBS treatment, respectively. This peak narrowing,\ntogether with the decreased ν (CH )/ν (CH ) intensity ratio and the pronounced shift\nas 2 s 2\nof both bands to lower wavenumbers, provides solid direct evidence for the suppression\nof alkyl chain conformational fluctuations. These observations indicate that the AEBS\nligands effectively restrict the dynamic motion of neighboring OLA molecules (Nat.\nCommun., 2024, 15, 9211; J. Am. Chem. Soc., 2020, 142, 13051; J. Am. Chem. Soc.,\n1999, 121, 5319). We have incorporated this rigorous FTIR analysis into the revised\nmanuscript.\nQ4. In AEBS-NPLs, weakened EPC suppresses exciton dissociation and increases\nexciton binding energy. This should reduce the PL lifetimes and the average lifetimes\nwhen exciton recombination dominates. The authors should clarify this point.\nReply:\nWe appreciate the reviewer’s insightful comment. We agree that, in general, an\nincreased E is expected to enhance radiative recombination and shorten the PL lifetime\nb\nwhen exciton recombination dominates. However, in strongly quantum-confined NPL\nsystems, the recombination kinetics may be influenced by more complex factors.\nIn this system, the recombination dynamics are simultaneously regulated by EP\ncoupling through both radiative and non-radiative pathways. Based on PLQY and TRPL\nanalyses (Fig. 3f and Supplementary Table 2), AEBS treatment leads to a significant\nreduction in the nonradiative rate (k ) from 0.0238 to 0.0115 ns-1, accompanied by an\nnr\nincrease in the radiative rate (k ) from 0.0406 to 0.0426 ns-1. It should be emphasized\nr\nthat in perovskites, defect trapping and exciton dissociation are typical phonon-assisted\nprocesses, the rates of which are closely related to the EP coupling strength (Nano-\nMicro Lett., 2024, 16, 178). Therefore, the weakening of EP coupling itself can\nsignificantly inhibit phonon-assisted carrier trapping, thereby reducing non-radiative\nrecombination.\nFurthermore, in strongly confined systems, the radiative recombination rate is not\nsolely determined by the electron-hole wavefunction overlap and may also be partially\ninfluenced by phonon-mediated transfer between bright and dark exciton states (Nano\nLett., 2020, 20, 7321; Nano Lett., 2022, 17, 7011; Nat. Commun., 2023, 14, 2426; Adv.\nSci., 2022, 9, 2103013). Therefore, this may account for the lack of a significant\nincrease in the radiative recombination rate. The extended lifetime in AEBS-NPLs\nprimarily originates from the inhibition of phonon-assisted non-radiative processes due\nto the weakened EP coupling, which is internally consistent with our proposed EP\ncoupling regulation mechanism. Notably, the coexistence of higher exciton binding\nenergy and extended PL lifetime in perovskites has been previously reported (Angew.\nChem. Int. Ed., 2024, 63, e202318777; Nat. Nanotechnol., 2025, 20, 507; Adv. Funct.\nMater., 2024, 2311554).\nQ5. The PL images in Figure 3g show that the degradation of the control sample is not\nuniform. Please provide an explanation for this nonuniformity.\nReply:\nWe clarify that the apparent spatial nonuniformity observed in the optical image\nof the Control-NPLs does not result from intrinsic material but from imaging artifacts.\nThe original image with the background is shown in Fig. R3. During UV excitation at\n60-100 °C, the PL intensity of the Control-NPLs decreases, increasing sample\ntransparency and revealing the texture of the aluminum-foil support and the black\nadhesive tape beneath the glass substrate. To avoid potential confusion, the image has\nbeen re-acquired and replaced in the revised manuscript (Fig. R4; Fig. 3g).\nFig. R3. Optical photograph of Control-NPLs with an aluminum-foil background under\nUV illumination (corresponding to Fig. 3g).\nFig. R4 (Fig. 3g). Evolution of PL intensity during thermal annealing from 20 to 100 °C,\nwith 10 °C increments and a 5 min hold at each temperature. Insets show the PL images\nof Control-NPLs film (left) and AEBS-NPLs film (right) annealed at different\ntemperatures.\nQ6. The manuscript states that both Joule heating and electric-field-induced\ndegradation are significantly suppressed. Could the authors elaborate on the mechanism\nbehind this suppression?\nReply:\nReduced Joule heating can be attributed to the mitigated EP coupling and\nimproved energy-level alignment. Weakened EP coupling enhances carrier mobility\nand suppresses phonon-assisted trapping (Fig. 3a-f). Meanwhile, the improved energy-\nlevel alignment reduces the hole-injection barrier and facilitates more balanced charge\ninjection (Fig. 3a,b and Supplementary Figs. 24,30). Together, these effects effectively\nlower the device series resistance (Adv. Mater., 2024, 37, 2412041; Nat. Rev. Chem.,\n2025, 9, 261; Nat. Commun., 2016, 7, 11755; ACS Energy Lett., 2017, 2, 1539; Nat.\nCommun., 2023, 14, 6441), mitigate nonradiative recombination losses (ACS Nano\n2016, 10, 9992; Nat. Photon., 2022, 16, 485; Adv. Mater., 2023, 35, 2209002; Nat.\nCommun., 2020, 11, 2712; Nano Lett., 2018, 18, 6645; ACS Nano 2019, 13, 11433),\nand consequently suppress Joule heating.\nThe suppression of electric-field-induced degradation is fundamentally linked to\nthe inhibition of halide ion migration and enhanced structural integrity. AEBS-NPLs\nexhibit a significantly higher ion migration activation energy of 184 meV compared to\n106 meV for Control-NPLs (Fig. R5), thereby hindering ion migration (Nat. Photon.,\n2017, 11, 726; Nat. Energy, 2020, 5, 131; Nat. Nanotechnol., 2024, 19, 638).\nMeanwhile, weakened EP coupling and improved energy-level alignment reduce series\nresistance and nonradiative losses, thereby alleviating the impact of Joule heating on\nion migration (Supplementary Fig. 39; Nat. Commun., 2024, 15, 6561). In addition,\nthe rigid vertical anchoring of AEBS ligands on the NPL surface constrains neighboring\nligand motion and lattice fluctuations (Fig. 1b), suppressing local structural\nrearrangements and avoiding perovskite degradation under high electric fields.\nThe relevant data have been added to the Supplementary Information (Supplementary\nFig. 40), and the corresponding analysis has been included in the main manuscript.\nFig. R5 (Supplementary Fig. 40). Determination of the ion migration activation\nenergy of NPLs. a,b, The time-dependent currents from 220 K to 310 K for Control-\nNPLs (a) and AEBS-NPLs (b), respectively. c,d, Temperature-dependence plots of ln(kT)\nversus 1000/T for Control-NPLs (c) and AEBS-NPLs (d).\nQ7. Although improved injection efficiency may contribute to a reduced turn-on\nvoltage, it is unclear from Figure 4d what primarily accounts for the observed decrease\nof 0.2-0.3 V. The authors should clarify this point.\nReply:\nIn response to the reviewer’s comment, we provide the following additional\nclarification. The observed 0.2-0.3 V reduction in turn-on voltage can be ascribed to the\nsynergistic effects of balanced carrier injection, efficient transport, and reduced\nnonradiative losses (Nature 2018, 562, 245; Sci. Adv., 2024, 10, eadp8473; Light Sci.\nAppl., 2025, 14, 50). After AEBS post-treatment, the interfacial energy-level alignment\nwas optimized (Supplementary Fig. 30), thereby lowering the hole injection barrier\nand enabling more balanced charge injection and radiative recombination at lower\nvoltages. In parallel, the rigid AEBS ligands pin surface OLA conformations, which\nweakens EP coupling, reduces carrier-phonon scattering, and enhances carrier mobility\nunder low electric fields (Supplementary Table 1). Building on the improved injection\nand transport, the suppressed EP coupling, together with the reduced defect density,\ninhibits phonon-assisted trap capture and nonradiative recombination, thereby lowering\nthe carrier density threshold required for efficient radiative recombination. Collectively,\nthese effects account for the reduced turn-on voltage, consistent with the faster response\nobserved in Tr-EL measurements (Fig. 4h). We thank the reviewer for the comment\nand have supplemented the manuscript accordingly.\nResponse to the comments from Reviewer #2\nThis manuscript reports a strategy to suppress electron-phonon (EP) coupling in CsPbI\n3\nnanoplatelets (NPLs) using a rigid ligand (AEBS) to achieve efficient pure-red light-\nemitting diodes (PeLEDs) with a narrow emission linewidth of 24 nm. While the study\naddresses an important topic in perovskite optoelectronics and presents an interesting\nligand-pinning concept, the manuscript suffers from several critical issues that\nundermine the validity of its central claims and the robustness of its conclusions. The\nevidence provided is insufficient to convincingly demonstrate that the observed\nimprovement is primarily due to the inhibition of EP coupling. Therefore, the\nmanuscript in its current form is not recommended for publication. Below are specific\nmajor concerns that must be adequately addressed:\nReply:\nWe are very grateful for the insightful comments and constructive suggestions,\nwhich have helped us to further improve our work. Below we provide point-by-point\nresponses to the referee’s comments and suggestions.\nQ1. The manuscript heavily relies on the claim that AEBS treatment suppresses EP\ncoupling, but the evidence is indirect. Key parameters for quantifying EP coupling, such\nas the Huang-Rhys factor or direct measurement of phonon modes via ultrafast\nspectroscopy, are not provided.\nReply:\nWe appreciate the reviewer’s professional suggestion, which motivated us to\nfurther strengthen the quantitative analysis of EP coupling. In the original manuscript,\nthe exciton-LO phonon coupling strength (Γ ) was extracted by fitting the temperature\nLO\ndependent PL linewidth, which is a well established method for evaluating EP coupling\n(Adv. Mater., 2023, 35, 2209002; Adv. Mater., 2024, 37, 2412041).\n\n(T) T  LO\ninh eE LO /(k B T) 1\nin which Γ represents the inhomogeneous broadening, σ is the exciton-acoustic\ninh\nphonon coupling coefficient, E represents the LO phonon energy and k is the\nLO B\nBoltzmann constant. In the low-temperature regime (< 110 K), the EP interaction is\npredominantly governed by acoustic phonons, while LO phonons dominate this\ninteraction in the high-temperature region. Therefore, the fitting above 110 K mainly\nconsiders the Γ and Γ terms (ACS Nano 2017, 11, 10834). To eliminate the\ninh LO\nuncertainty associated with the E , Raman spectroscopy data were incorporated to\nLO\nconstrain the fitting parameters (Supplementary Fig. 20) (ACS Nano 2017, 11, 10834;\nNat. Commun., 2016, 7, 11755). Accordingly, Fig. 2i in the revised manuscript has\nbeen updated with the constrained fitting, enabling a more rigorous and reliable\nquantification. The extracted Γ of the AEBS NPLs (36.6 meV) is significantly smaller\nLO\nthan that of the control sample (63.5 meV) (Fig. R6). The observed trend is fully\nconsistent with that reported in the original manuscript and does not affect the\nconclusions. These quantitative results clearly demonstrate that the AEBS NPLs exhibit\nweaker EP coupling.\nIn accordance with the reviewer’s suggestions, we further quantified the EP\ncoupling using the Huang-Rhys factor (S). Because the PL spectra contain contributions\nfrom the zero-phonon line (ZPL), phonon sidebands, and inhomogeneous broadening\narising from variations in crystal size, shape, and composition, a more rigorous\nmultimode Brownian oscillator (MBO) model was employed to simulate the spectra\n(Supplementary Fig. 21a,b) and extract S (J. Phys. Chem. Lett. 2024, 15, 11015; Sci.\nChina Phys. Mech. Astron., 2024, 67, 234212; J. Phys. Chem. C 2019, 123, 5128; Appl.\nPhys. Lett., 2006, 88, 083123).\n1  \nI ()  f ( )d Re exp[i( +S )t-g*(t)]dt\nPL  0 eg eg 0 eg LO\nf( )exp[2W2(  0)2]\neg eg eg\n1  2S 3\ng(t)  d LO [1coth(/2k T)](eit it1)\n2  2[22 ( 2 2)2] B\nLO\nHere, f(ω ) represents the inhomogeneous broadening, ω 0 denotes the angular\neg eg\nfrequency of the ZPL position, and g*(t) is the complex conjugate of the spectral\nresponse function g(t). k is the Boltzmann constant, ω is the angular frequency of\nB LO\nthe primary phonon coupled to the exciton, and γ represents the damping constant that\naccounts for the broadening induced by the low-frequency acoustic phonon bath.\nThe results show that S increases with temperature for both Control-NPLs and\nAEBS-NPLs, while the S values of the Control-NPLs are consistently larger than those\nof the AEBS-NPLs (Fig. R7). As the S directly reflects the EP coupling strength (J.\nPhys. Chem. Lett. 2024, 15, 11015; Nat. Photon., 2025, 19, 952.), these results indicate\nweaker EP coupling in the AEBS-NPLs.\nThe relevant data have been added to the Supplementary Information (Supplementary\nFig. 23), and the manuscript has been revised accordingly.\nFig. R6 (Fig. 2i). Fitted curves of FWHM as a function of temperature for Control-\nNPLs and AEBS-NPLs films.\nFig. R7 (Supplementary Fig. 23). S obtained from the MBO model versus temperature.\nQ2. The authors claim AEBS vertically pins on the CsPbI NPL surface. However, there\n3\nis a lack of direct structural evidence. How can the proposed perpendicular\nconfiguration be conclusively verified? Meanwhile, the proposed mechanism where\nAEBS \"pins\" dynamic OLA ligands is speculative. No direct experimental evidence is\nprovided.\nReply:\nWe appreciate the reviewer’s insightful comment. We agree that directly resolving\nthe precise orientation of organic ligands on NPL surfaces is important. However, due\nto the limitations of current experimental techniques, the ligand geometry at the atomic\nscale still cannot be unambiguously determined under realistic surface coverage\nconditions. Consequently, ligand configurations on the nanocrystals are generally\ninferred from density functional theory (DFT) calculations and further validated by\nspectroscopic evidence (Fig. R8, Science 2024, 384, 189; Nature 2024, 631, 73; Nature\n2023, 5, 830; Angew. Chem. Int. Ed., 2025, e19659; Nat. Commun., 2024, 15, 9211).\nFollowing this established framework, our DFT calculations systematically compare\npossible binding motifs of AEBS on the CsPbI NPL surface and identify the head-end\n3\ncoordination configuration as the energetically most favorable (Supplementary Fig. 1).\nThis configuration involves simultaneous coordination between the sulfonyl group and\nsurface Pb2+ ions, as well as hydrogen bonding between −NH groups and surface I-\n2\nions, which naturally leads to a preferentially upright orientation of the AEBS\nbackbone. XPS and FTIR analyses further support this assignment by confirming the\nexpected coordination environment and hydrogen-bonding interactions at the NPL-\nligand interface (Supplementary Fig. 12).\nRegarding the proposed \"pinning\" of dynamic OLA ligands, we emphasize that\nthis mechanism is not inferred from theory alone. Molecular dynamics calculations\nshow a clear reduction in temporal fluctuations of the distances between terminal\ncarbon atoms of adjacent OLA ligands after AEBS incorporation (Supplementary Fig.\n2). Experimentally, FTIR spectroscopy provides a sensitive probe of alkyl-chain\nconformational order (Fig. R9, Nat. Commun., 2024, 15, 9211; J. Am. Chem. Soc.,\n2020, 142, 13051; J. Am. Chem. Soc., 1999, 121, 5319; Molecules 2020, 25, 5633; J.\nAm. Chem. Soc., 1987, 109, 3559). Upon AEBS treatment, the ν (CH )/ν (CH )\nas 2 s 2\nintensity ratio decreases, accompanied by a systematic shift to lower wavenumbers and\nnarrowing of both vibrational bands (Fig. 1e). These spectral changes are well-\nestablished signatures of enhanced alkyl chain order and suppressed conformational\ndynamics of OLA ligands.\n[FIGURE REDACTED]\nFig. R8. Representative literature examples demonstrating the determination of ligand\nadsorption configurations on perovskite surfaces using DFT calculations (Science 2024,\n384, 189; Nature 2024, 631, 73; Angew. Chem. Int. Ed., 2025, e19659).\n[FIGURE REDACTED]\nFig. R9. Representative literature examples illustrating the use of the ν (CH ) and\nas 2\nν (CH ) stretching vibrations to assess the conformational order of alkyl chains (Nat.\ns 2\nCommun., 2024, 15, 9211; J. Am. Chem. Soc., 1999, 121, 5319; Molecules 2020, 25,\n5633).\nQ3. How can the authors rule out that the observed effects are not simply due to superior\nsurface passivation by AEBS, rather than the proposed \"pinning\" of OLA ligands? The\nstudy lacks a control experiment using a structurally similar but flexible ligand to isolate\nthe effect of ligand rigidity from other chemical properties.\nReply:\nWe thank the reviewer for the insightful comment on distinguishing surface defect\npassivation from rigid-ligand pinning. To decouple these two effects, we designed\nsystematic control experiments using oleylammonium iodide (OLAI) and 3-Amino-1-\npropanesulfonamide (APSA). OLAI treatment increases the surface coverage of OLA\nand effectively passivates surface defects without introducing new ligand species (Fig.\nR10a,b). In contrast, APSA shares the same head and tail functional groups as AEBS\nbut lacks a rigid aromatic backbone, serving as a flexible analogue to isolate the role of\nligand rigidity (Fig. R10c,d). As shown in Fig. R11, both OLAI-NPLs and APSA-NPLs\nexhibit higher PLQYs than Control-NPLs, confirming effective defect passivation.\nHowever, their PL linewidths remain largely unchanged, indicating that defect\npassivation alone does not lead to emission narrowing. FTIR analysis further reveals\nthat both increasing OLA coverage and introducing a flexible APSA ligand fail to\nrestrict the conformational freedom of the alkyl chains (Fig. R12 and Fig. 1e).\nTemperature-dependent PL linewidth fitting shows that Γ slightly increases for\nLO\nOLAI-NPLs compared to Control-NPLs due to the higher density of long-chain OLA,\nwhereas Γ for APSA-NPLs shows only a minor reduction compared to Control-NPLs\nLO\nand remains significantly larger than that of AEBS-NPLs (Fig. R13 and Fig. 2i). These\nresults demonstrate that flexible ligands or increased surface passivation alone cannot\neffectively suppress EP coupling, and that rigid AEBS ligand pinning plays a dominant\nrole in doing so.\nThe relevant data have been included in the Supplementary Information\n(Supplementary Figs. 14-16,22), and the manuscript has been correspondingly\nexpanded.\nFig. R10 (Supplementary Fig. 14). a-d, Chemical structures of OLA (a), OLAI (b),\nAEBS (c) and APSA (d).\nFig. R11 (Supplementary Fig. 15). a, PL spectra of Control-NPLs, OLAI-NPLs and\nAPSA-NPLs. b, PLQY of Control-NPLs, OLAI-NPLs, APSA-NPLs and AEBS-NPLs.\nFig. R12 (Supplementary Fig. 16). FTIR spectra of Control-NPLs, OLAI-NPLs and\nAPSA-NPLs.\nFig. R13 (Supplementary Fig. 22). Temperature-dependent PL spectra of both CsPbI\nNPLs (a) and APSA-NPLs (b). c,d, Fitted curves of FWHM as a function of temperature\nfor OLAI-NPLs (c) and APSA-NPLs films (d).\nQ4. The reported maximum EQE of 29.8% is an outlier in the statistical distribution\n(19.3% to 29.8%), and the average EQE is 23.2 ± 2.4%. The large standard deviation\nsuggests significant device-to-device variation, raising a concern about the\nreproducibility and the representativeness of the champion device.\nReply:\nWe thank the reviewer for the careful examination of the EQE statistics and\ndevice-to-device variation. The reported EQE statistics are compiled from devices\nindependently fabricated across multiple batches over an extended period, rather than\nfrom a single optimized experiment. It is important to note that perovskite\noptoelectronic properties are intrinsically sensitive to surface states and processing\nconditions. In addition, in our system, precise control of the AEBS/SBA-15 ligand post-\ntreatment process remains challenging. These factors inevitably introduce batch-to-\nbatch variability under practical fabrication conditions and thereby induce performance\nvariation. Despite this variability, the devices exhibit an average EQE of 23.2±2.4%,\nwith all devices outperforming the best Control-NPLs based PeLEDs. The maximum\nEQE of 29.8% lies within the continuous tail of the statistical distribution rather than\nrepresenting an isolated outlier, with a substantial fraction of devices exceeding 25%.\nSimilar EQE statistical distributions have also been widely reported in many previously\nreported high-performance LEDs (Fig. R14, Nat. Commun., 2019, 10, 3624; Nat.\nPhoton., 2025, 19, 952; Nat. Commun., 2023, 14, 397; Nature 2021, 591, 72),\nsupporting the representativeness and reproducibility of the results.\n[FIGURE REDACTED]\nFig. R14. a-c, EQE statistical histogram of PeLEDs (Nat. Commun., 2019, 10, 3624;\nNat. Photon., 2025, 19, 952; Nat. Commun., 2023, 14, 397; Nature 2021, 591, 72).\nQ5. The improved device performance is primarily attributed to suppressed EP coupling.\nHowever, other factors—such as enhanced surface passivation, improved energy level\nalignment, or reduced defect density—could also or more significantly contribute to\nthese improvements. How can the authors deconvolve the contribution of suppressed\nEP coupling from other beneficial effects of AEBS treatment?\nReply:\nWe appreciate the reviewer’s professional suggestion to deconvolve the multiple\nphysical factors influenced by AEBS. To rigorously isolate the specific contribution of\nEP coupling suppression, we designed a systematic comparative study: (1) defect-\npassivated NPLs using OLAI without introducing new ligand species (OLAI-NPLs);\n(2) NPLs treated with APSA (APSA-NPLs) which shares same head and tail functional\ngroups as AEBS but lacks a rigid backbone (Fig. R10).\nOLAI-NPLs exhibit effective defect passivation (Fig. R11b). However, FTIR\nanalysis shows that the increased surface coverage of OLA ligands enhances\nconformational disorder (Fig. R12) and the resulting EP coupling (Fig. R13c).\nMoreover, OLAI-NPLs show no significant narrowing of the emission linewidth, nor\ndo they exhibit improvements in electrical conductivity or device EQE relative to the\ncontrol samples (Figs. R11a, R15a, and R16a). These results demonstrate that defect\npassivation alone cannot account for the substantial performance enhancement\nobserved for AEBS-modified devices.\nAPSA possesses the same head and tail functional groups as AEBS but lacks a\nrigid backbone. Unlike AEBS, the APSA fails to effectively suppress the\nconformational freedom of the alkyl chains, do not significantly reduce the EP coupling\nstrength, and also do not exhibit substantial improvements in electrical conductivity or\ndevice EQE (Figs. R12, R13d, R15b and R16b). These findings effectively rule out the\npossibility that other chemical contributions of AEBS, such as its short-chain nature\nand defect passivation by the functional groups, are the primary drivers of the observed\nsubstantial performance improvement.\nIn contrast, only the rigid AEBS treatment achieves substantial EP coupling\nsuppression, which we identify as the dominant mechanism for suppressing exciton\ndissociation, reducing carrier-phonon scattering, and achieving narrow emission and\nenhanced mobility. In addition, AEBS pinning suppresses lattice vibrations and local\nstructural rearrangements (Fig. 1b), enhancing lattice stability. EP coupling suppression\nfurther promotes efficient charge transport and reduces nonradiative recombination,\nwhich lowers Joule heating (Supplementary Fig. 39), mitigates ion migration, and\nenhances device stability.\nAlthough AEBS modification optimizes energy-level alignment, promotes\nbalanced charge injection, and lowers the turn-on voltage (Fig.4d), the simultaneous\nimprovements in device efficiency, operational stability, and emission linewidth\ncorrelate more strongly with the pronounced enhancements in the intrinsic optical\nproperties, electrical conductivity, and stability of the AEBS-NPLs. Energy-level\nalignment alone is insufficient to account for such a substantial and concerted\nenhancement, indicating that it is not the primary driving factor for the improved device\nperformance. Instead, the effective suppression of EP coupling plays a dominant role\nand, in synergy with energy-level optimization and defect passivation, endows the\ndevices with superior optoelectronic performance.\nThe relevant data have been included in the Supplementary Information\n(Supplementary Figs. 25 and 37), and the manuscript has been correspondingly\nexpanded.\nFig. R15 (Supplementary Fig. 25). a,b, Conductivity characterization of the OLAI-\nNPLs (a) and APSA-NPLs (b).\nFig. R16 (Supplementary Fig. 37). a,b, The EQE-J curves for both OLAI-NPLs based\nPeLED (a) and APSA-NPLs based PeLED (b).\nQ6. The interpretation of hot-carrier cooling based on TRPL and TA is indirect. The\nrise times in TRPL are influenced by multiple factors, such as trap-assisted processes\nor dielectric screening, not solely EP coupling.\nReply:\nWe thank the reviewer for the insightful comments on ultrafast spectroscopic\ndynamics. We agree that the rise times observed in TRPL and TA are influenced by\nmultiple factors. To address this, we performed additional detailed characterizations to\nidentify the dominant factors governing the rise times in this NPL system.\nTo address whether defects affect the rise time, we first performed power-\ndependent transient absorption (TA) measurements under low pump fluence, where a\nlow pump fluence was deliberately employed to avoid interference from Auger\nrecombination and phonon bottleneck effects. If the rise-time difference were governed\nby trap states, a clear fluence dependence would be expected (Angew. Chem. Int. Ed.\n2022, 61, e202111443; J. Am. Chem. Soc., 2019, 141, 3532). However, the rise time\nshows negligible fluence dependence (Fig. R17a-f), indicating that trap states are not\nthe dominant factor controlling the observed rise-time variation. Further support is\nprovided by comparative experiments on OLAI-NPLs. Although effective defect\npassivation is achieved, the increased OLA coverage enhances alkyl-chain disorder and\nstrengthens EP coupling (Figs. R11b, R12, R13c), leading to an even shorter TA rise\ntime compared with Control-NPLs (Fig. R17g). Taken together, these results rule out\ndefects as the primary factor governing the rise time in the ultrafast spectroscopic\ndynamics.\nRegarding dielectric screening effects, further clarification is provided. The\nlimited surface coverage of AEBS on the NPLs suggests that its modulation of Coulomb\ninteractions within the perovskite is expected to be weak. Moreover, previous studies\nhave reported that even ligands with substantially different dipole moments yield nearly\nidentical hot-carrier cooling dynamics, indicating that electrostatic or dielectric effects\nmake a negligible contribution (Nat. Commun., 2017, 8, 1300). Further support is\nprovided by comparative experiments on APSA-NPLs. APSA lacks an aromatic ring\nand thus cannot effectively pin OLA ligands, resulting in ineffective suppression of EP\ncoupling (Figs. R12 and R13d). APSA shares the same head and tail functional groups\nas AEBS; although it does not provide comparable dielectric screening, it can serve as\na reference. Consistently, APSA-NPLs show no significant prolongation of the rise time\nin TA dynamics compared with Control-NPLs, further excluding dielectric screening as\nthe dominant origin of the observed dynamical changes (Fig. R17h).\nThe relevant data have been included in the Supplementary Information\n(Supplementary Fig. 18), and the manuscript has been correspondingly expanded.\nFig. R17 (Supplementary Fig. 18). a-f, Normalized TA dynamics of Control-NPLs\nunder different pump fluences. g-i, Normalized TA dynamics of OLAI-NPLs (g), APSA-\nNPLs (h), and AEBS-NPLs (i). Although the instrument response function (IRF) caused\nslight deviations in the kinetic traces compared to the original manuscript, it did not\nsignificantly affect the extraction of the rise time.\nQ7. The SCLC measurements show that the mobility in AEBS-NPLs increased, but the\nanalysis did not distinguish between the decrease of EP coupling and other factors, such\nas the improved film morphology or the reduced trap density.\nReply:\nTo deconvolve the multiple factors that may influence carrier mobility, we\nperformed additional comparative analyses combining structural characterization with\ncarefully designed control experiments.\nSEM and AFM characterizations in Supplementary Fig. 31 show that AEBS-\nNPLs and Control-NPLs exhibit no intrinsic differences in film continuity, surface\nroughness, or overall morphology. These results exclude morphology-driven transport\nimprovement as the dominant origin of enhanced mobility.\nWe further conducted control experiments analogous to those discussed in Q5.\nOLAI treatment primarily induces defect passivation; however, the charge-transport\ncapability of OLAI-NPLs shows no significant improvement compared with that of\nControl-NPLs (Fig. R15a and Fig. 3c). Similarly, APSA, which is structurally\nanalogous to AEBS but lacks a rigid backbone, cannot effectively pin OLA ligands and\nfails to efficiently suppress EP coupling. APSA-NPLs present a modest increase in\nconductivity, which remains much weaker than that observed in AEBS-NPLs. (Fig.\nR15b and Fig. 3c).\nThese comparative results demonstrate that the potential defect passivation effect\nof functional groups and the short-chain nature of AEBS are insufficient to account for\nthe substantial mobility enhancement observed in AEBS-NPLs. When considered\ntogether with the pronounced suppression of EP coupling, they indicate that the\nsignificantly improved mobility in AEBS-NPLs primarily originates from reduced\ncarrier scattering associated with weakened EP coupling.\nThe relevant data have been included in the Supplementary Information\n(Supplementary Fig. 25), and the manuscript has been correspondingly\nexpanded.\nResponse to the comments from Reviewer #3\nI co-reviewed this manuscript with one of the reviewers who provided the listed\nreports. This is part of the Nature Communications initiative to facilitate training in\npeer review and to provide appropriate recognition for Early Career Researchers who\nco-review manuscripts.\nReply:\nWe sincerely appreciate the reviewer’s time and valuable feedback, which have\nhelped improve the quality of our work. We have provided responses to the\ncorresponding comments.\nResponse to the comments from Reviewer #4\nThe manuscript presents a clear and compelling strategy to suppress electron-phonon\n(EP) coupling in CsPbI nanoplatelets (NPLs), which has long been a critical\n3\nbottleneck limiting the spectral purity and device performance of pure-red PeLEDs.\nThe introduction of a rigid ligand—4-(2-aminoethyl)benzenesulfonamide (AEBS)—as\na “rigid-ligand pinning” motif is conceptually strong and addresses the fundamental\nissue of lattice softness and dynamic disorder originating from long-chain oleylamine\nligands. The authors convincingly demonstrate that AEBS anchoring suppresses lattice\nvibrations, reduces EP coupling strength, and narrows both PL and EL linewidths.\nImportantly, the achieved device metrics—an EL FWHM of 24 nm, a peak EQE\nof up to 29.8%, and an operational T of 128.2 h—are among the best reported for\n50\npure-red PeLEDs and highlight the technological relevance of the approach. The\nmanuscript further benefits from a broad and well-integrated set of spectroscopic\nanalyses (TRPL, TA, temperature-dependent PL, Raman), providing multi-angle\nevidence for weakened EP interactions. Overall, the work represents a significant and\ntimely contribution to advancing perovskite NPL-based optoelectronics.\nWhile this work has many merits, we believe that several fundamental issues\nrequire further clarification and supporting evidence.\nRegarding these points, I comment on points below\nReply:\nWe thank the reviewer for the positive appraisal and recommendation on our work.\nIn light of the referee’s constructive suggestions, we provide point-by-point responses\nto the comments in the following.\nQ1. <Lack of quantitative evaluation of AEBS incorporation>\nAlthough FTIR and XPS analyses confirm AEBS adsorption, the manuscript does not\noffer quantitative information regarding the extent of ligand exchange. The relative\nproportions of AEBS and native OLA ligands remain unclear.\nTo substantiate the mechanistic claims, quantitative measurements (e.g., TGA,\nquantitative NMR, or XPS ratio analysis) should be provided to determine the ligand\ncoverage and the AEBS/OLA ratio.\nReply:\nWe thank the reviewer for the suggestion. To determine the OLA/AEBS ratio and\ntotal ligand density on AEBS-NPLs, we employed a combination of 1H nuclear magnetic\nresonance (1H NMR) spectroscopy and thermogravimetric analysis (TGA)\n(Fig. R18) (J. Am. Chem. Soc., 2024, 146, 29104; Angew. Chem. Int. Ed., 2022, 61,\ne202111443). The specific details are as follows:\nThe ligand density (D ), defined as the number of ligands per unit surface area of\nL\nthe NPLs, can be calculated as follows:\n(m /M )N\nD  L L A\nL (m A )/( V )\nNPL NPL NPL NPL\nwhere m is the total mass of the ligands, M is the relative molecular mass of the\nL L\ncorresponding ligand, N is Avogadro constant, m is the mass of ligand-free NPLs,\nA NPL\nρ is the density of CsPbI NPLs (4.84 g cm-3), V is the volume of a single NPL,\nNPL 3 NPL\nand A is the surface area of a single NPL. TGA yields m of 2.515 mg and 2.912\nNPL NPL\nmg and m of 0.300 mg and 0.338 mg for the Control-NPLs and AEBS-NPLs,\nL\nrespectively. Together with the 1H NMR determined OLA to AEBS molar ratio of\napproximately 1:0.12 and the NPL dimensions, the surface ligand densities are\ncalculated to be ~1.45 and 1.50 nm-2 for the Control-NPLs and AEBS-NPLs,\nrespectively.\nThe relevant data have been included in the Supplementary Information\n(Supplementary Fig. 13).\nFig. R18 (Supplementary Fig. 13). a, TGA curves of Control-NPLs and AEBS-NPLs. b,\n1H NMR spectra of Control-NPLs and AEBS-NPLs.\nQ2. <Generalizability and mechanistic clarity of the SBA-15 assisted slow-release\nmethod>\nThe use of SBA-15 as a slow-release matrix to mitigate structural degradation during\nAEBS treatment is intriguing, but its generality remains ambiguous. It is unclear\nwhether this approach applies to other highly polar or rigid ligands.\nAdditionally, evidence for the AEBS release kinetics from SBA-15 is absent. Providing\nadsorption/desorption profiles or release-time dependence would greatly strengthen the\nmethodological section.\nReply:\nWe thank the reviewer for the valuable suggestion. In response, we have conducted\nfurther supplementary experiments.\nSBA-15, as a well-established biomedical sustained-release carrier (Angew. Chem.\nInt. Ed., 2007, 46, 7548; J. Am. Chem. Soc., 2006, 128, 8116), exhibits the potential to\naccommodate highly polar ligands. Therefore, the use of SBA-15 for the sustained\nrelease of polar ligands is not limited to AEBS alone. However, the efficacy of this\nstrategy in mitigating perovskite structural degradation during post-treatment remains\ndependent on factors such as ligand polarity and solvent affinity. Consequently, each\nspecific ligand system requires case-by-case evaluation.\nTo address the reviewer’s concern regarding insufficient evidence for the release\nkinetics of AEBS from SBA-15, the nitrogen adsorption-desorption isotherms of\npristine SBA-15 and AEBS-loaded SBA-15 composites (Fig. R19; Supplementary Fig.\n5), already provided in the Supplementary Information of the original manuscript,\nindicate that AEBS partially occupies and blocks the mesopores of SBA-15 rather than\nbeing merely adsorbed on the external surface. In addition, we directly probed the\nrelease behavior of AEBS from SBA-15 by monitoring the time-dependent PL\nevolution in solution (Fig. R20). In this experiment, AEBS powder and AEBS/SBA-15\ncomposite powder were separately placed at the bottom of cuvettes filled with hexane,\nand the PL intensity of the supernatant was continuously monitored as a function of\ntime to track AEBS release. Compared with AEBS, the AEBS/SBA-15 exhibits a\nmarkedly slower increase in PL intensity, demonstrating a significantly reduced release\nrate under the regulation of SBA-15.\nThe relevant data have been included in the Supplementary Information\n(Supplementary Fig. 6), and the manuscript has been correspondingly expanded.\nFig. R19 (Supplementary Fig. 5). Brunauer-Emmett-Teller (BET) measurements. a,b,\nNitrogen adsorption-desorption isotherm diagram of pristine SBA-15 (a) and AEBS\nloaded SBA-15 composites (b), respectively.\nFig. R20 (Supplementary Fig. 6). Release-time dependence PL spectra of AEBS and\nAEBS/SBA-15 powders. a,b, Time-dependent PL spectra of pristine AEBS (a) and\ncorresponding PL intensity evolution (b). c,d, Time-dependent PL spectra of AEBS\nunder SBA slow-release (c) and corresponding PL intensity evolution (d).\nQ3. Beyond EP coupling suppression, AEBS—owing to its strong polarity and rigid\nstructure—may influence trap densities, surface dipoles, and ion migration. UPS data\nsuggest modifications to energy alignment, yet the manuscript does not fully explore\nthe broader electronic implications.\nA more detailed analysis separating EP-related effects from defect passivation and ion-\ntransport effects would provide a more complete and accurate interpretation of the\nresults.\nReply:\nWe appreciate the reviewer’s professional suggestion to deconvolve the multiple\nphysical factors influenced by AEBS. To rigorously isolate the specific contribution of\nEP coupling suppression, we designed a systematic comparative study: (1) defect-\npassivated NPLs using oleylammonium iodide (OLAI) without introducing new ligand\nspecies (OLAI-NPLs), (2) NPLs treated with 3-Amino-1-propanesulfonamide (APSA)\n(APSA-NPLs) which shares same head and tail functional groups as AEBS but lacks a\nrigid backbone (Fig. R21).\nOLAI-NPLs exhibit effective defect passivation (Fig. R22b). However, FTIR\nanalysis shows that the increased surface coverage of OLA ligands enhances\nconformational disorder (Fig. R23) and the resulting EP coupling (Fig. R24c).\nMoreover, OLAI-NPLs show no significant narrowing of the emission linewidth, nor\ndo they exhibit improvements in electrical conductivity or device EQE relative to the\ncontrol samples (Figs. R22a, R25a, and R26a). These results demonstrate that defect\npassivation alone cannot account for the substantial performance enhancement\nobserved for AEBS-modified devices.\nAPSA possesses the same head and tail functional groups as AEBS but lacks a\nrigid backbone. Unlike AEBS, the APSA fails to effectively suppress the\nconformational freedom of the alkyl chains, do not significantly reduce the EP coupling\nstrength, and also do not exhibit substantial improvements in electrical conductivity or\ndevice EQE (Figs. R23, R24d, R25b and R26b). These findings effectively rule out the\npossibility that other chemical contributions of AEBS, such as its short-chain nature\nand defect passivation by the functional groups, are the primary drivers of the observed\nsubstantial performance improvement.\nIn contrast, only the rigid AEBS treatment achieves substantial EP coupling\nsuppression, which we identify as the dominant mechanism for suppressing exciton\ndissociation, reducing carrier-phonon scattering, and achieving narrow emission and\nenhanced mobility. In addition, AEBS pinning suppresses lattice vibrations and local\nstructural rearrangements (Fig. 1b), enhancing lattice stability, combined with the\nreduction in Joule heating by the concomitant decrease in EP coupling (Supplementary\nFig. 39), which mitigates ion migration and further improves device stability (discussed\nin detail in Q4).\nAlthough AEBS modification optimizes energy-level alignment, promotes\nbalanced charge injection, and lowers the turn-on voltage (Fig.4d), the simultaneous\nimprovements in device efficiency, operational stability, and emission linewidth\ncorrelate more strongly with the pronounced enhancements in the intrinsic optical\nproperties, electrical conductivity, and stability of the AEBS-NPLs. Energy-level\nalignment alone is insufficient to account for such a substantial and concerted\nenhancement, indicating that it is not the primary driving factor for the improved device\nperformance. Instead, the effective suppression of EP coupling plays a dominant role\nand, in synergy with energy-level optimization and defect passivation, endows the\ndevices with superior optoelectronic performance.\nThe relevant data have been included in the Supplementary Information\n(Supplementary Figs. 14-16,22,25,37), and the manuscript has been correspondingly\nexpanded.\nFig. R21 (Supplementary Fig. 14). a-d, Chemical structures of OLA (a), OLAI (b),\nAEBS (c) and APSA (d).\nFig. R22 (Supplementary Fig. 15). a, PL spectra of Control-NPLs, OLAI-NPLs and\nAPSA-NPLs. b, PLQY of Control-NPLs, OLAI-NPLs, APSA-NPLs and AEBS-NPLs.\nFig. R23 (Supplementary Fig. 16). FTIR spectra of Control-NPLs, OLAI-NPLs and\nAPSA-NPLs.\nFig. R24 (Supplementary Fig. 22). Temperature-dependent PL spectra of both CsPbI\nNPLs (a) and APSA-NPLs (b). c,d, Fitted curves of FWHM as a function of temperature\nfor OLAI-NPLs (c) and APSA-NPLs films (d).\nFig. R25 (Supplementary Fig. 25). a,b, Conductivity characterization of the OLAI-\nNPLs (a) and APSA-NPLs (b).\nFig. R26 (Supplementary Fig. 37). a,b, The EQE-J curves for both OLAI-NPLs based\nPeLED (a) and APSA-NPLs based PeLED (b).\nQ4. While the reported operational stability is excellent, the manuscript provides little\nmechanistic insight into degradation processes.\nAnalyses such as EL spectral evolution under bias, voltage rise during operation, or ion\nmigration-related signatures would help clarify the origin of the improved device\nlifetime and reinforce the claims of structural stabilization.\nReply:\nWe thank the reviewer for the professional suggestion. For PeLEDs, performance\ndegradation is closely linked to electric- and thermally driven ion migration in\nperovskites as well as the stability of the perovskite lattice structure (Nat. Nanotechnol.,\n2024, 19, 638; ACS Energy Lett., 2019, 4, 779; Acc. Chem. Res., 2016, 49, 286; ACS\nNano, 2016, 10, 693; Nature, 2024, 631, 73).\nWe investigated the mechanism underlying the suppression of electric-field-\ninduced degradation. The evolution of the EL spectra under different driving voltages\nreveals a pronounced spectral broadening in Control-NPLs based PeLEDs (Fig. R27a),\nwhich is attributed to severe halide ion migration (Nat. Commun., 2024, 15, 6561). Ion\nmigration induces lattice degradation and increased interfacial energy barriers, leading\nto a rise in operating voltage and substantial Joule heating under constant-current\noperation (Fig. R27b) (Nat. Photon., 2021, 15, 630). In contrast, AEBS-NPLs exhibit\na higher activation energy (E ) for ion migration (Fig. R28), which hinders ion\na\nmigration (Nat. Photon., 2017, 11, 726; Nat. Energy 2020, 5, 131; Nat. Nanotechnol.,\n2024, 19, 638), and the AEBS pinning effect suppresses lattice vibrations and local\nstructural rearrangements, thereby enhancing lattice stability (Fig. 1b). In addition,\nweakened EP coupling and improved energy-level alignment reduce series resistance\nand nonradiative losses, thereby alleviating the impact of Joule heating on ion migration\n(Supplementary Fig. 39; Nat. Commun., 2024, 15, 6561). Collectively, these factors\nresult in a substantial enhancement of device operational lifetime.\nThe relevant data have been added to the Supplementary Information (Supplementary\nFigs. 32,38,40), and the corresponding analysis has been included in the main\nmanuscript.\nFig. R27 (Supplementary Figs. 32 and 38). a, EL spectra of the Control-NPLs based\nPeLED under different driving voltages. b, Time-dependent driving voltage of PeLEDs\nunder constant current density operation.\nFig. R28 (Supplementary Fig. 40). Determination of the ion migration activation\nenergy of NPLs. a,b, The time-dependent currents from 220 K to 310 K for Control-\nNPLs (a) and AEBS-NPLs (b), respectively. c,d, Temperature-dependence plots of ln(kT)\nversus 1000/T for Control-NPLs (c) and AEBS-NPLs (d).\nQ5. <Oversimplified attribution of emission broadening in the control NPLs>\nThe authors attribute the broader emission linewidth of the control sample primarily to\nenhanced EP coupling. However, other factors, including trap-mediated recombination,\nsurface reconstruction, and OLA desorption, are also likely contributors, particularly in\nlight of the stability data presented in the SI.\nA more nuanced discussion acknowledging these additional mechanisms is\nrecommended\nReply:\nWe systematically analyzed the mechanisms governing emission linewidth\nbroadening. TEM characterization revealed that the Control-NPLs and AEBS-NPLs are\nhighly consistent in terms of thickness uniformity (Fig. R29 and Fig. 1c), effectively\nruling out thickness inhomogeneity as the dominant factor responsible for the linewidth\ndifference. Control experiments using OLAI demonstrated that, despite enhancing\nsurface OLA coverage, effectively passivating iodine vacancies, and repairing the\nsurface structure, these treatments did not induce a significant narrowing of the\nemission linewidth (Fig. R22a). This indicates that defect passivation or surface\nreconstruction is not the primary source of the observed linewidth difference.\nFurthermore, at ~80 K, EP coupling contributes minimally, and Control-NPLs and\nAEBS-NPLs show comparable emission linewidths (Fig. 2i). With increasing\ntemperature, EP coupling induced broadening becomes dominant, particularly in\nControl-NPLs, indicating that their broader linewidth primarily arises from stronger EP\ncoupling.\nThe relevant data have been included in the Supplementary Information\n(Supplementary Fig. 11b).\nFig. R29 (Supplementary Fig. 11b). STEM image of vertically oriented Control-NPLs\nfor thickness determination.\nResponse to the comments from Reviewer #5\nHua et al. developed a rigid-ligand pinning strategy by partially substituting native OLA\nligands with 4-(2-aminoethyl)benzenesulfonamide (AEBS) ligands via post treatment.\nThe AEBS ligand substitution leads to a more ordered surface with lower exciton-\nphonon coupling and high photoluminescent quantum efficiency. Based on the AEBS\ntreated NPLs, the authors can fabricated record efficiency for NPL LED devices with\naverage EQE of 23.2% (best pixel EQE 29.8%) and an operational lifetime of 128.2h\nat 100 cd m-2. The work is well written and supported by adequate experimental\nevidence to support their claim. I would suggest it to be published in Nat. Commun.\nafter the following points being addressed.\nReply:\nWe thank the reviewer for the positive evaluation of our work. Detailed point-by-\npoint responses to the comments are provided below.\nQ1. The authors perform fs-TA spectroscopy to investigate early kinetics of the hot\ncarrier cooling as indirect evidence of carrier-phonon coupling. The faster cooling of\nthe controlled NPLs may also influence by surface traps as the early time hot carrier\ncooling can also be governed by direct trapping process of the hot carriers. Could the\nauthor elaborate how to de-couple the factors from hot carrier trapping and electron\nphonon coupling to the influence of the early cooling kinetics. I would suggest to\ninclude a fluence dependent TA study to see if the cooling kinetic changes upon\ndifferent excitation fluence. If the cooling time difference is caused by trap, it would be\nmediated at when increasing from low to high excitation power due to trap filling. At\nthe meantime, since Frohlich coupling at sub ps time scale is intrinsic material\nproperties, it would be not influence by pump fluence.\nReply:\nWe thank the reviewer for the suggestion and guidance. Following the\nrecommendation, we have supplemented the study with pump-fluence-dependent TA\nmeasurements. To avoid interference from phonon bottleneck effects at high fluence\nthat could slow down hot-carrier cooling, the experiments were conducted at low\nexcitation fluence. Although the instrument response function caused slight deviations\nin the kinetic traces compared to the original manuscript, it did not significantly affect\nthe extraction of the rise time. The results show that variations in pump fluence have a\nminimal impact on the rise time of the TA dynamics in Control-NPLs, indicating that\ncarrier trapping by defects does not play a dominant role in the observed hot-carrier\ncooling dynamics (Fig. R30).\nThe relevant data have been included in the Supplementary Information\n(Supplementary Fig. 18a-f), and the manuscript has been correspondingly expanded.\nFig. R30 (Supplementary Fig. 18a-f). a-f, Normalized TA dynamics of Control-NPLs\nunder different pump fluences.\nQ2. Since the AEBS also simultaneously passivate surface traps, it would be nice to\nisolate the effect of trap passivation to surface reordering in terms of explaining\nelectron-phonon coupling strength obtained from cryo-PL measurement. The presence\nof surface trap may also introduce extra phonon modes in the lattice which affect the\ncoupling strength, would it possible to compare a sample with extra OLAm or OA\nligands passivation, so we reduce the surface traps but keep the surface more disordered\nso that we can compare the effect only due to AEBS pinning effect.\nReply:\nWe thank the reviewer for the professional suggestions and experimental guidance.\nHere, we introduced oleylammonium iodide (OLAI) to modify the NPLs (Fig. R31a).\nOLAI treatment increases the surface coverage of OLA without introducing new ligand\nspecies, leading to effective defect passivation, as reflected by the enhanced PLQY (Fig.\nR31c). However, the PL linewidths remain largely unchanged, indicating that defect\npassivation alone does not narrow the emission (Fig. R31b). Temperature-dependent\nPL linewidth fitting shows that Γ slightly increases in OLAI-NPLs compared with\nLO\nControl-NPLs (Fig. R32 and Fig. 2i), due to the higher density of long-chain OLA.\nThese results demonstrate that increased surface passivation alone cannot effectively\nsuppress EP coupling, and that rigid AEBS ligand pinning plays a dominant role in\ndoing so.\nThe relevant data have been included in the Supplementary Information\n(Supplementary Figs. 14b,15 and 22a,c), and the manuscript has been correspondingly\nexpanded.\nFig. R31 (Supplementary Fig. 14b,15). a, Chemical structures of OLAI. b, PL spectra\nof Control-NPLs, OLAI-NPLs and APSA-NPLs. c, PLQY of Control-NPLs, OLAI-NPLs,\nAPSA-NPLs and AEBS-NPLs.\nFig. R32 (Supplementary Fig. 22a,c). Temperature-dependent PL spectra of CsPbI\nNPLs. b, Fitted curves of FWHM as a function of temperature for OLAI-NPLs.\nQ3. Figure 2g shows the PL shifted to a higher energy when increasing from cryo\ntemperature to room temperature. In contrast, the treated sample in Fig.2h, show a blue\nshift then red shift from below 100K to 300 K. Could the author elaborate the reasons?\nDoes it to do with ligand reconstructions? With AEBS ligands, after certain temperature\nis reached, it thermally actives the ligands which triggering stronger interactions with\nneighbouring nanoplatelets that leads to more delocalized carriers that gives lower\nenergy emission?\nReply:\nWe thank the reviewer for their attention to the temperature-dependent PL peak\nshift. Through a systematic comparison of Control-NPLs, AEBS-NPLs, OLAI-NPLs,\nand 3-Amino-1-propanesulfonamide(APSA) treated NPLs (APSA-NPLs), we observed\nthat, upon heating from low temperature to room temperature, the PL peak exhibits an\ninitial blue-shift followed by a red-shift in all samples (Fig. R33 and Supplementary\nFigs. 21 and 22), indicating that this behavior is not induced by thermally activated\nprocesses or surface reconstruction associated with specific ligands.\nSuch non-monotonic spectral shifts have been reported in previous studies (Fig.\nR34) (Adv. Sci., 2021, 8, 2100084; J. Phys. Chem. Lett., 2021, 12, 1137; Appl. Phys.\nLett., 2019, 114, 101902). Based on literature reports, we suggest that the non-\nmonotonic temperature-dependent bandgap evolution is jointly governed by transitions\nin lattice thermal expansion behavior and EP coupling. From low temperature up to\napproximately 200 K, the initial blue-shift of the PL peak is primarily caused by in-\nplane positive thermal expansion (PTE), in which the expansion of the inorganic lattice\nleads to an increase in the bandgap. In the temperature range of 200-300 K, the ultrathin\nnanoplatelets exhibit uniaxial negative thermal expansion (NTE) along the stacking\ndirection, with the lattice thickness contracting anomalously as the temperature\nincreases. This lattice contraction, induced by dynamic octahedral tilting and stress\nfrom the surface ligand sublattice, together with the enhancement of EP coupling at\nelevated temperatures, which leads to bandgap renormalization and narrowing,\ncollectively overcomes the in-plane expansion effect and results in the observed red-\nshift of the PL peak at higher temperatures (Fig. R35, Nano Lett., 2023, 23, 2148).\nFig. R33. Temperature-dependent PL peak positions of NPLs. a, Control-NPLs. b,\nOLAI-NPLs. c, APSA-NPLs. d. AEBS-NPLs.\nFig. R34. Temperature-dependent PL peak positions of the perovskite samples, showing\nan initial blueshift followed by a redshift upon heating from low temperature to room\ntemperature (Adv. Sci., 2021, 8, 2100084; J. Phys. Chem. Lett., 2021, 12, 1137; Appl.\nPhys. Lett., 2019, 114, 101902).\nFig. R35. a, Variable-temperature PL spectra at representative points between 12 and\n3\nthe out-of-plane (d ) and in-plane (d ) dimensions. Between 258 and 298 K, negative\nz xy\nthermal expansion is observed along the axial axis of higher elastic compliance (Nano\nLett., 2023, 23, 2148).\nQ4. In Fig. S13, the Pb-I stretching modes gets restricted after AEBS treatment as the\npeak at 108 cm-1 gets narrower. Is there a reason that this mode is being selectively\nconstrained? The I-Pb-I at 55 cm-1 seems not being affected as the peak width stays\nmore or less constant.\nReply:\nWe thank the reviewer for the careful evaluation of the Raman spectra. Although\nthe measurement is limited by the instrument, a rough estimation indicates that the\nRaman peak of AEBS-NPLs at ~55 cm-1 remains narrower than that of Control-NPLs,\nsuggesting that the peak narrowing is not a selective effect. It should be clarified that\nthe interpretation of the Raman signals in the original manuscript may have been\nsignificantly affected by the formation of PbI during measurement (as discussed in\nto minimize PbI interference and updated the original Raman data. Importantly, these\n2\nupdated data are fully consistent with our previous conclusions (Fig. R36 and Table\nR1).\nFig. R36 (Supplementary Fig. 20). Raman spectra of both CsPbI NPLs.\nFWHM (cm-1)\nPeak 1 Peak 2\nControl-NPLs 8.0 14.2\nAEBS-NPLs 6.4 10.9\nQ5. Does the Raman peak intensity at 232 cm-1 for PbI formation changed overtime\n2\nduring the measurement, or this is coming from pre-exist PbI on the surface.\nWe conducted a systematic analysis of the origin of PbI . The samples were\n2\nprepared and transferred under inert gas protection, and combined with the XRD results\nreported in the manuscript (Supplementary Fig. 10), the possibility of pre-existing PbI\n2\non the NPLs surface due to exposure to moisture or oxygen can be excluded. We\nattribute the formation of PbI primarily to laser-induced decomposition during\n2\nmeasurement. To verify this, Raman measurements were performed under vacuum\nusing low laser power. The results show that prolonged irradiation significantly\nincreases the intensity of the 232 cm-1 Raman signal (Fig. R37), indicating that PbI\n2\nformation is indeed induced by the laser. To minimize potential interference from\nexcessive PbI , the Raman data collected under low-power conditions were used to\n2\nupdate the original manuscript data (Fig. R36). The conclusions derived from the\nupdated data remain consistent with the previous ones. We sincerely thank the reviewer\nfor their careful evaluation.\nFig. R37. Comparison of Raman spectra for Control-NPLs in the pristine state and\nafter 5 min of continuous laser irradiation.\nQ6. For PeLEDs, typical outcoupling efficiency is around 20-25% for Lambertian\nemission. Fig4c shows there are marginal difference in emission profile, is there a\ncertain device structure or photonic structures in the device, such as face-down\nalignment of NPls that can leads to potential higher outcoupling for the maximum\nefficiency of 29.8%? Has the authors done any optical simulations in their device to\ncheck the thermotical efficiency limit?\nReply:\nWe thank the reviewer for the professional comments regarding the device\noutcoupling efficiency. We analyzed the emitting dipole orientation of the NPL film and\nperformed optical simulations of the PeLED.\nFirst, grazing incidence small-angle X-ray scattering (GISAXS) characterizations\nwere performed on both Control-NPLs and AEBS-NPLs films (Fig. R38a,b). The\nresults show that both films are dominated by a face-down orientation (Nano Lett., 2023,\n23, 2148; ACS Appl. Nano Mater., 2025, 8, 8588).\nWe further assumed two extreme cases, namely random orientation (isotropic\ndipole distribution) and 100% face-down orientation, and performed optical\nsimulations of the theoretical EQE limit by incorporating the experimentally measured\nPLQY of AEBS-NPLs. The air mode represents the theoretically simulated EQE limit.\nThe simulation results show that, under the same emissive layer thickness, the EQE\nlimits corresponding to 23.4% for random orientation of NPLs and 32.7% for 100%\nface-down orientation, respectively, and both vary with the thickness of the emissive\nlayer (Fig. R38c,d). This demonstrates that a face-down orientation can significantly\nenhance the outcoupling efficiency, consistent with reported literature (Nat. Photon.,\n2024, 18, 586). The experimentally achieved EQE of 29.8% falls between the two\ntheoretical limits, which is reasonable for NPLs exhibiting a predominantly face-down\norientation.\nThe relevant data have been included in the Supplementary Information\n(Supplementary Fig. 36), and the manuscript has been correspondingly expanded.\nFig. R38 (Supplementary Fig. 36). NPL arrangement and optical mode analysis in\nPeLEDs. a,b, GISAXS patterns obtained for the Control-NPLs (a) and AEBS-NPLs (b).\nc,d, Relative mode contributions versus perovskite thickness for PeLEDs based on\nrandomly oriented NPLs (c) and 100% face-down oriented NPLs (d).\nQ7. Additionally, Figure S23 demonstrated the performance matrix for the best device,\nbut the current density and maximum luminance of the best device is much lower than\nthe average device after treatment and the controlled device shown in Main Figure 4d.\nIs there a specific reason?\nReply:\nHere, we discuss the point raised by the reviewer. During multi-batch device\nfabrication, unavoidable uncertainties in the volumetric calibration of NPL solutions\nlead to concentration variations, which in turn cause fluctuations in the microscopic\nthickness of the emissive layer, NPL stacking density, and dipole orientation ratio. A\nthicker and more densely packed emissive layer is beneficial for enhancing light\noutcoupling efficiency (Fig. R38c,d). Meanwhile, an increased NPL thickness\nmitigates carrier leakage and, by reducing the carrier density, suppresses excessive\nexciton quenching, which collectively favors the realization of a high EQE. However,\na thicker emissive layer also increases the resistance to charge injection and transport,\ntypically resulting in lower current density and luminance, accompanied by a higher\nturn-on voltage. Such thickness-induced trade-offs are commonly observed in PeLEDs\n(Fig. R39; Nat. Commun., 2018, 9, 3541). The coexistence of high EQE and low\nbrightness is a normal phenomenon in PeLEDs (Fig. R40; Nature, 2021, 591, 72; Sci.\nAdv., 2025, 11, eadp9595).\nFig. R39. Effect of emissive layer thickness on PeLED device performance. a-e, Current\ndensity-voltage (a), luminance-voltage (b), EQE-current density (c), power efficiency-\ncurrent density (d) and current efficiency- current density (e) characteristics of PeLEDs\nmade from perovskite films with different thickness: Device I (125 nm), Device II\n(80 nm), Device III (60 nm), and Device IV (40 nm) (Nat. Commun., 2018, 9, 3541).\n[FIGURE REDACTED]\nFig. R40. a, Current density-voltage (J-V) and luminance-voltage (L-V) curves. b,\nEQE-current density curves (Nature, 2021, 591, 72)."}, {"round": 2, "reviewer_comments": {"reviewer_1": "The manuscript has been substantially improved. However, two points require clarification before acceptance.\n1.Please provide quantitative thickness and lateral size distribution statistics to exclude the possibility that the linewidth\nnarrowing arises from reduced inhomogeneous broadening.\n2.Although AEBS modification clearly mitigates efficiency roll-off at high current density, the manuscript should explicitly\ndiscuss the origins of this improvement.", "reviewer_2": "The authors have addressed most of my concerns. I would like to recommend acceptance of the revised paper for\npublication.", "reviewer_3": "I co-reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co-review manuscripts.", "reviewer_4": "I thank the authors for their thorough and constructive responses to my previous comments.\nThe revised manuscript and the expanded Supplementary Information have significantly strengthened both the mechanistic\nanalysis and the overall clarity of the work.\nQ1 – Quantification of AEBS incorporation.\nThe addition of TGA, ¹H NMR analysis, and XPS characterization substantially improves the description of the ligand\nenvironment after AEBS treatment. While the determination of absolute surface coverage remains semi-quantitative, the\nreported OLA/AEBS ratio and ligand density analysis are sufficient to support the proposed surface-modulation mechanism\nwithin the scope of this study.\nQ2 – Validity of the SBA-15 slow-release strategy.\nThe release-dependent PL measurements and BET characterization reasonably demonstrate that SBA-15 moderates ligand\ndelivery and prevents structural degradation during post-treatment. Although a fully quantitative release-kinetics analysis is\nnot provided, the experimental evidence adequately supports the functional role of the slow-release strategy.\nQ3 – Evidence for suppression of electron–phonon coupling.\nThe clarified linewidth fitting procedure, explicit reporting of ΓLO values, Huang–Rhys factor extraction using the MBO\nmodel, and supporting TA and Raman analyses collectively provide a coherent and internally consistent mechanistic\npicture. While complete disentanglement of defect passivation and EP-coupling effects is intrinsically challenging, the\npresented data sufficiently substantiate EP-coupling suppression as a dominant contributing factor.\nQ4 – Device stability mechanism.\nThe addition of ion-migration activation energy measurements and temperature-dependent analyses convincingly connects\nmaterials-level modification with device-level stability enhancement. This aspect has been substantially strengthened in the\nrevision.\nQ5 – Exclusion of alternative explanations for linewidth narrowing.\nControl experiments using OLAI and APSA provide reasonable comparative evidence that defect passivation alone cannot\naccount for the observed linewidth narrowing. Minor wording adjustments may be advisable to avoid overly exclusive\nstatements, but no further experimental evidence is required.\nOverall, my primary scientific concerns have been adequately addressed. The manuscript now presents a well-supported\nmechanism linking ligand rigidity, suppressed electron–phonon coupling, and improved PeLED performance.", "reviewer_5": "All questions rised in previous round have been addressed. I have no further questions and can suggest to publish the work\nas is."}, "author_response": "Response to the comments from Reviewer #1\nThe manuscript has been substantially improved. However, two points require clarification before acceptance.\nReply:\nWe sincerely thank the reviewer for the recognition of our work, and we provide the\nfollowing clarifications to address the points raised.\n1. Please provide quantitative thickness and lateral size distribution statistics to exclude\nthe possibility that the linewidth narrowing arises from reduced inhomogeneous\nbroadening.\nReply:\nFollowing the reviewer’s suggestions, we performed a quantitative size distribution\nanalysis of the pure-red CsPbI NPLs, whose emission is primarily governed by\n3\nthickness-induced quantum confinement, with only minor contributions from lateral\nsize variation. The results show no significant changes in the size distribution before\nand after ligand post-treatment, and the NPLs maintain a uniform thickness. These\nobservations indicate that the PL linewidth narrowing of the AEBS-NPLs does not\noriginate from improved size uniformity (Fig. R1).\nThe relevant data have been included in the Supplementary Information\n(Supplementary Fig. 11e-j).\nFig. R1 (Supplementary Fig. 11e-j). Histograms of the size distributions for the NPLs.\na-c, Length (a), width (b), and thickness (c) distributions of the Control-NPLs. d-f,\nLength (d), width (e), and thickness (f) distributions of the AEBS-NPLs.\n2. Although AEBS modification clearly mitigates efficiency roll-off at high current\ndensity, the manuscript should explicitly discuss the origins of this improvement.\nReply:\nWe sincerely thank the reviewer for this constructive question. Additional discussion\nhas been provided in the revised manuscript (Lines 195-198) to clarify the origin of\nthe suppressed efficiency roll-off in AEBS-NPLs based devices. The relevant\ndiscussion is reproduced below:\n“AEBS-NPLs based PeLEDs exhibit suppressed efficiency roll-off, arising from\nweakened EP coupling that mitigates exciton dissociation induced quenching and\nimproved energy-level alignment that promotes balanced charge injection and\nsuppresses Auger recombination7,60,61 (Fig. 3d and Supplementary Fig. 30).”\nReference:\n7: Nature 2022, 611, 688; 60: J. Am. Chem. Soc., 2021, 143, 19128; 61: ACS Nano\n2024, 18, 31485\nResponse to the comments from Reviewer #2\nThe authors have addressed most of my concerns. I would like to recommend\nacceptance of the revised paper for publication.\nReply:\nWe sincerely thank the reviewer for the positive recognition of our revisions to the\nmanuscript and for the recommendation for publication.\nResponse to the comments from Reviewer #3\nI co-reviewed this manuscript with one of the reviewers who provided the listed reports.\nThis is part of the Nature Communications initiative to facilitate training in peer review\nand to provide appropriate recognition for Early Career Researchers who co-review\nmanuscripts.\nReply:\nWe sincerely thank the co-reviewer for the time and effort devoted to the careful\nassessment of our manuscript and for the positive feedback. We are grateful for the\nrecognition of our work and for the support for publication.\nResponse to the comments from Reviewer #4\nI thank the authors for their thorough and constructive responses to my previous\ncomments.\nThe revised manuscript and the expanded Supplementary Information have\nsignificantly strengthened both the mechanistic analysis and the overall clarity of the\nwork.\nQ1 Quantification of AEBS incorporation.\nThe addition of TGA, 1H NMR analysis, and XPS characterization substantially\nimproves the description of the ligand environment after AEBS treatment. While the\ndetermination of absolute surface coverage remains semi-quantitative, the reported\nOLA/AEBS ratio and ligand density analysis are sufficient to support the proposed\nsurface-modulation mechanism within the scope of this study.\nQ2 Validity of the SBA-15 slow-release strategy.\nThe release-dependent PL measurements and BET characterization reasonably\ndemonstrate that SBA-15 moderates ligand delivery and prevents structural degradation\nduring post-treatment. Although a fully quantitative release-kinetics analysis is not\nprovided, the experimental evidence adequately supports the functional role of the\nslow-release strategy.\nQ3 Evidence for suppression of electron-phonon coupling.\nThe clarified linewidth fitting procedure, explicit reporting of Γ values, Huang-Rhys\nLO\nfactor extraction using the MBO model, and supporting TA and Raman analyses\ncollectively provide a coherent and internally consistent mechanistic picture. While\ncomplete disentanglement of defect passivation and EP-coupling effects is intrinsically\nchallenging, the presented data sufficiently substantiate EP-coupling suppression as a\ndominant contributing factor.\nQ4 Device stability mechanism.\nThe addition of ion-migration activation energy measurements and temperature-\ndependent analyses convincingly connects materials-level modification with device-\nlevel stability enhancement. This aspect has been substantially strengthened in the\nrevision.\nQ5 Exclusion of alternative explanations for linewidth narrowing.\nControl experiments using OLAI and APSA provide reasonable comparative evidence\nthat defect passivation alone cannot account for the observed linewidth narrowing.\nMinor wording adjustments may be advisable to avoid overly exclusive statements, but\nno further experimental evidence is required.\nOverall, my primary scientific concerns have been adequately addressed. The\nmanuscript now presents a well-supported mechanism linking ligand rigidity,\nsuppressed electron-phonon coupling, and improved PeLED performance.\nReply:\nWe are pleased that our responses have overall addressed the reviewer’s main concerns\nand sincerely appreciate the reviewer’s recognition of our work. For the remaining\nwording issue in Q5, we have made the corresponding revisions as detailed below:\nWe systematically analyzed the mechanisms governing emission linewidth broadening.\nTEM characterization revealed that the Control-NPLs and AEBS-NPLs are highly\nconsistent in terms of thickness uniformity (Supplementary Fig. 11), suggesting that\nthickness inhomogeneity is unlikely to be the dominant factor contributing to the\nobserved linewidth difference. Control experiments using OLAI demonstrated that,\ndespite enhancing surface OLA coverage, effectively passivating iodine vacancies, and\nrepairing the surface structure, these treatments did not induce a significant narrowing\nof the emission linewidth (Supplementary Fig. 15a). These observations suggest that\ndefect passivation or surface reconstruction alone cannot fully account for the observed\nlinewidth narrowing. Furthermore, at ~80 K, EP coupling contributes minimally, and\nControl-NPLs and AEBS-NPLs show comparable emission linewidths (Fig. 2i). With\nincreasing temperature, EP coupling induced broadening becomes dominant,\nparticularly in Control-NPLs, consistent with stronger EP coupling being the main\ncontributor to their broader linewidth.\nResponse to the comments from Reviewer #5\nAll questions rised in previous round have been addressed. I have no further questions\nand can suggest to publish the work as is.\nReply:\nWe sincerely thank the reviewer for the rigorous and professional evaluation. The\nvaluable insights provided during the revision process were instrumental in improving\nthis work. We are grateful for the recommendation for publication."}, {"round": 3, "reviewer_comments": {"reviewer_1": "The authors have satisfactorily addressed all the concerns raised. I have no further concerns and recommend the\nmanuscript for publication in its current form."}, "author_response": ""}]

Decision letter