# Impact of Solvent Additives on Enhancing the Performance and Robustness of Green Solvent-Processed Indoor Organic Solar Cells

Anass Khodr, Ignacio Ballesteros García, Takeshi Watanabe, Hidehiro Sekimoto, Donia Fredj, Hasan Alkhatib, Sadok Ben Dkhil, Olivier Margeat, Christine Videlot-Ackermann, Carmen Maria Ruiz, et al.

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## To cite this version:

Anass Khodr, Ignacio Ballesteros García, Takeshi Watanabe, Hidehiro Sekimoto, Donia Fredj, et al. Impact of Solvent Additives on Enhancing the Performance and Robustness of Green Solvent-Processed Indoor Organic Solar Cells. Solar RRL, 2025, 10.1002/solr.202500363. hal-05228654

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RESEARCH ARTICLE

OPEN ACCESS

# Impact of Solvent Additives on Enhancing the Performance and Robustness of Green Solvent-Processed Indoor Organic Solar Cells

Anass Khodr¹,² ID
Ignacio Ballesteros García¹
Takeshi Watanabe³ ID
Hidehiro Sekimoto⁴
Donia Fredj²
Hasan Alkhatib²
Sadok Ben Dkhil²
Olivier Margeat¹ ID
Christine Videlot-Ackermann¹ ID
Carmen Maria Ruiz⁵ ID
Jörg Ackermann¹

¹Aix Marseille University, CNRS, CINaM, Marseille, France | ²Dracula Technologies, Valence, France | ³Industrial Application Division, Japan Synchrotron Radiation Research Institute (JASRI), Hyogo, Japan | ⁴Department of Physical Science and Materials Engineering, Iwate University, Morioka, Japan | ⁵Aix Marseille University, CNRS, IM2NP, Marseille, France

**Correspondence:** Christine Videlot-Ackermann (christine.videlot-ackermann@cnrs.fr) | Carmen Maria Ruiz (carmen.ruiz-herrero@im2np.fr) | Jörg Ackermann (jorg.ackermann@cnrs.fr)

**Received:** 15 May 2025 | **Revised:** 11 July 2025 | **Accepted:** 4 August 2025

**Funding:** Collaborative Research Agreement between CNRS-Dracula Technologies, Grant/Award Number: 225847; Ministère de l'Éducation Nationale, de la Formation professionnelle, de l'Enseignement Supérieur et de la Recherche Scientifique, Grant/Award Number: 2020/0978; Collaborative research with Japan; Synchrotron Radiation Research Institute, Grant/Award Number: 2021A2031; Agence Nationale de la Recherche, Lab-Com IOPV-Lab, Grant/Award Number: ANR-21-LCV2-0001-01

**Keywords:** ambient condition processing | green formulation | indoor | non-fullerene acceptors | organic photovoltaic | sustainable energy

## ABSTRACT

The rapid growth of the Internet of Things increases the demand for efficient indoor organic photovoltaics (OPVs). This study introduces a novel TPD-3F:FCC-Cl blend, achieving power conversion efficiencies exceeding 20% and a near 1 V open-circuit voltage ($V_{oc}$) under 2000Lx illumination. The study examines the blend's potential for indoor energy harvesting, focusing on processing under industrially relevant conditions. The effects of solvent additives, specifically tetralin and diphenyl ether (DPE), are evaluated using spin-coating and doctor-blading techniques under both inert and ambient conditions. The use of DPE as a greener additive significantly improves film uniformity, device reproducibility, and performance stability across varying light intensities and layer thicknesses. Structural analysis confirms favorable face-on orientation and enhanced crystallinity for FCC-Cl domains, with DPE-based formulations yielding the most uniform films. Reproducibility metrics further show DPE's superiority over traditional additives, making it promising for industrial-scale indoor OPV applications. The findings highlight the strong potential of the TPD-3F:FCC-Cl blend for high-efficiency, sustainable indoor OPVs, particularly when processed with non-halogenated solvents and scalable techniques like blade coating.

## 1 Introduction

The rapid expansion of the Internet of Things (IoT) is driving an increasing demand for efficient and autonomous energy solutions to power connected devices, particularly in indoor environments [1, 2]. Among the available energy-harvesting technologies, organic photovoltaics (OPVs) stand out as a highly

promising option due to their unique advantages, including tunable light absorption, flexibility, lightweight construction, low toxicity, and potential for scalable production [3]. Recent advancements in OPV materials have led to significant improvements in indoor power conversion efficiencies (PCEs), with values now exceeding 36% [4], thus underlining their strong potential for self-powered IoT applications.

This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

© 2025 The Author(s). Solar RRL published by Wiley-VCH GmbH.
This progress has been largely driven by the development of non-fullerene acceptors (NFAs), notably those from the Y-series, such as Y6 [4, 5], BTP-eC9 [6], and Y6-O [7]. These materials have enabled high efficiency under both simulated sunlight and low-intensity indoor lighting. To further enhance indoor OPV performance, NFAs with medium to large bandgaps (~1.7–2 eV) have been developed. Notable examples include LBT-SCL [8], IO-4Cl [9], GS-ISO [10], FCC-Cl [11], and FTCC-Br [12], which offer higher open-circuit voltages ($V_{oc}$), a key parameter for indoor light harvesting. Among these, FCC-Cl has attracted particular attention due to its high indoor efficiencies reaching up to 33% and its impressive $V_{oc}$ values of 0.91 V and 1.02 V under 500 Lx and 20 000 Lx, respectively [13]. Furthermore, FCC-Cl shows encouraging long-term stability, making it a particularly promising material for the development of robust and efficient indoor OPVs [13].

In parallel with advances in acceptors, several donor polymers such as PTQ10, PM6, D18, and PB2 have been developed to produce high-performance OPVs [13–15]. Among these, D18 has emerged as a particularly promising donor polymer due to its ability to achieve high efficiencies with various acceptor materials [16]. For example, solar cells based on D18:FCC-Cl blends have demonstrated PCEs exceeding 29% under indoor lighting. However, D18 presents two significant limitations that hinder its practical deployment. First, it exhibits poor thickness tolerance, when the active layer thickness increases to industrially relevant values (≈300 nm) performance degrades significantly (from ~29% to 22.6%) especially due to a decline in the fill factor (from 79.8% to 64.1%) [14]. Second, D18 suffers from poor processability, as it typically requires halogenated solvents and lacks compatibility with scalable coating methods for safer and environmentally friendly manufacturing [14].

To address these challenges, the wide-bandgap polymer TPD-3F has emerged as a promising alternative donor for indoor applications [17]. It is compatible with non-halogenated solvents such as o-xylene and offers high $V_{oc}$, good ambient-processability, and improved thickness tolerance. TPD-3F is well-suited for scalable techniques such as spin-coating and blade-coating in air. When paired with NFAs like ITIC-4F, TPD-3F-based devices have reached indoor efficiencies above 26%, although $V_{oc}$ values remain relatively low (~0.75 V under fluorescent light at 1000Lx), which hinders its use for indoor IoT applications [17].

While the indoor performance of OPV is now highly competitive with other technologies, a critical barrier to industrial adoption is the ability to replicate such high efficiencies under scalable and environmentally friendly processing conditions. Most high-performance organic solar cells are still processed using halogenated solvents (e.g., chloroform (CF), chlorobenzene (CB)) often in combination with additives like 1,8-diiodooctane (DIO), tetralin, or chloronaphthalene (CN). These solvents pose environmental and health hazards and are unsuitable for large-scale, sustainable manufacturing [18]. Consequently, there is an urgent need to develop non-halogenated materials and eco-friendly ink formulations that maintain high PCEs while being compatible with scalable, industrial processing techniques. Recent studies have begun addressing this issue, although efficiencies with non-halogenated solvent systems have typically remained below 20% [16].

While progress has been made in solvent selection, to the best of our knowledge, no advanced studies have yet explored the use of eco-friendly solvent additives in combination with non-halogenated solvents to further enhance indoor OPV performance. Additionally, there remains a need to increase $V_{oc}$ and improve the robustness and reproducibility of the processing conditions to fully enable industrial deployment of high-efficiency indoor OPV technologies.

To address these limitations, this study presents, for the first time, the TPD-3F:FCC-Cl blend as a novel donor-acceptor system designed to achieve enhanced $V_{oc}$ while remaining compatible with sustainable, non-halogenated solvent systems and additives. This new blend builds upon the known benefits of FCC-Cl, which provides improved $V_{oc}$ compared to ITIC-4F in TPD-3F: ITIC-4F blends [18], and the superior processability and thickness tolerance of TPD-3F compared to D18 in D18:FCC-Cl systems [14]. We propose that this combination represents a promising pathway toward high-efficiency and environmentally friendly indoor energy harvesting. In addition, we report the use of diphenyl ether (DPE) as a solvent additive for indoor OPV applications. DPE is considered a greener alternative to tetralin, recently applied in inkjet printing [19], and has demonstrated the ability to enhance crystallinity and device performance in outdoor OPVs [20].

To investigate these hypotheses, we evaluate the morphology, crystallinity, and photovoltaic performance of TPD-3F:FCC-Cl blends processed with various solvent systems: oxylene (Ox), oxylene with tetralin (Ox:Tet), and oxylene with DPE (Ox: DPE). We assess the impact of these additives on film quality, device efficiency, and overall reproducibility. To further address scalability, we explore blade coating under ambient conditions as a route toward industrial processing, with particular emphasis on increasing active layer thickness, a key factor for roll-to-roll and large-area manufacturing. Additionally, we examine reproducibility, film quality, thickness tolerance, and efficiency under both inert and ambient environments, demonstrating the practical potential of the TPD-3F:FCC-Cl system for scalable, high-performance indoor OPVs.

## 2 | OPVs Based on TPD-3F:FCC-Cl Blend Processed under Inert Conditions

The first phase of our study focuses on evaluating the processing and the performance of the TPD-3F:FCC-Cl blend by employing spin-coating process under inert conditions, utilizing various solvent systems: oxylene (Ox), oxylene with tetralin (Ox:Tet), and oxylene with diphenyl ether (Ox:DPE). The absorption spectra of the mixture exhibit significant similarity across the three solutions examined (Figure S1, Supporting Information). The active layer was deposited under identical conditions (speed, time, and volume) for all formulations in an inverted device architecture as ITO/ZnO/TPD-3F: FCC-Cl/MoO$_3$/Ag with an active area of 0.16 cm$^2$, as detailed in the experimental part. Film thicknesses were measured using a profilometer, with values averaged from at minimum of three independent measurements.
<figure><img src="image_3.png" /><figcaption>**FIGURE 1** | *J*–*V* curves under AM1.5G illumination (a) and in dark (b) of photovoltaic devices based on spin-coated TPD-3F:FCC-Cl blends processed under inert atmosphere with different solution processing conditions (Ox, Ox:Tet, and Ox:DPE).</figcaption></figure>

The performance of the TPD-3F:FCC-Cl system was initially evaluated under standard 1 sun illumination (AM1.5G) to establish a benchmark. As shown in Figure 1a and summarized in Table 1, devices processed with different formulations (Ox, Ox:Tet, and Ox: DPE) demonstrated PCE of 9.4%, 9.7%, and 10.3%, respectively. All formulations exhibited high $V_{oc}$ of at least 1.1 V, along with short-circuit current densities ($J_{sc}$) ranging between 12.9 and 14.4 mA/cm². Figure 1b illustrates the dark *J*–*V* curves of one of the best samples for each formulation, indicating that samples containing DPE exhibit the lowest dark current. Additionally, the formulation Ox:DPE demonstrates the highest shunt resistance ($R_{sh}$) in the dark with mean value of 2343 MΩ·cm², compared to lower values for Ox:Tet and Ox, at 133 and 0.15 MΩ·cm², respectively. These values were calculated as the average $R_{sh}$ across all functional devices and are presented in Table S1 and Figure S2, Supporting Information. Devices were also tested under 2700 and 4000 K LED light with intensities ranging from 200 to 5000 Lx (Figure S4, Tables S2 and S3, Supporting Information). Figure 2 summarizes the photovoltaic parameters evolution as a function of light intensity with a 2700 K LED illumination. At 1000Lx, devices processed with Ox achieved 17% as maximum PCE, while those with Ox:Tet exceeded 20%. The highest efficiency was observed with Ox:DPE, surpassing 22%. The higher PCE for Ox:DPE aligns with findings reported in the literature, where improved photovoltaic performance under low illumination conditions were addressed to higher shunt resistance and lower dark current [21–23]. The $V_{oc}$ values for these devices reach 0.98 V for Ox:Tet and 0.96 V for Ox:DPE samples under 1000Lx illumination, respectively. Furthermore, FF analysis across varying light intensities showed that Ox:DPE devices maintained the highest FF, ranging from 68% at 200 Lx to 70% at 5000 Lx. Ox:Tet-based devices exhibited lower FF values, ranging from 65% at 200 Lx to 69% at 5000 Lx. In contrast, Ox devices exhibited clearly lower FF.

Similarly, $J_{sc}$ and $P_{max}$ follow the same trend, with the DPE-based sample exhibiting the highest values at 1000Lx with 107 µA/cm² and 72 µW/cm², respectively. To understand the superior performance of Ox:DPE processed devices, we investigate the recombination mechanisms under indoor conditions by determine the ideality factor for each formulation using the average values of $V_{oc}$ and $J_{sc}$ under indoor illumination at different light intensities as represented in Figure 3a. For Ox-based samples, an atypical trend was observed, characterized by two distinct slopes: one for low-light intensity flux up to 1000Lx, and another for high-light flux. Accordingly, two ideality factors were calculated for these regions, yielding values of 6 and 1.6, respectively. The unusually high ideality factor at lower light intensities suggests increased trap-assisted recombination and charge degradation under these conditions [24, 25], likely due to the higher sensitivity to defects and impurities when fewer charge carriers are photogenerated under low illumination intensity. This behavior reflects a transition to a more favorable transport regime, as higher light intensity compensates for trap-induced losses, resulting in an improvement in the ideality factor at higher illumination levels. Although an ideality factor of 1.6 is still high, it represents a significant improvement over the low-intensity regime, suggesting that the device becomes less limited by trap-assisted recombination as light intensity increases. Under high illumination intensities, more charge carriers are generated, allowing for increased charge extraction by mitigating the effects of traps. In contrast, the Ox:Tet and Ox:DPE formulations exhibited a single, consistent trend across the entire light intensity range, resulting in ideality factor values of 1.73 and 1.48, respectively. The lower ideality factor observed for DPE-based samples suggests more efficient charge extraction with reduced trap-assisted recombination compared to Ox:Tet. This trend aligns with the shunt

<table><caption>**TABLE 1** | Photovoltaic parameters under AM1.5G condition of photovoltaic devices based on spin-coated TPD-3F:FCC-Cl blends processed under inert atmosphere with different solution processing conditions (Ox, Ox:Tet, and Ox:DPE). Cells area is 0.16 cm².</caption><thead><tr><th>Solution</th><th>Thickness (nm)</th><th>V<sub>oc</sub> (V)</th><th>J<sub>sc</sub> (mA/cm<sup>2</sup>)</th><th>FF (%)</th><th>PCE (%) (PCEmax)</th><th>R<sub>sh</sub> (ohm.cm<sup>2</sup>)</th><th>R<sub>s</sub> (ohm.cm<sup>2</sup>)</th></tr></thead><tbody><tr><td>Ox</td><td>95</td><td>1.120 ± 0.003</td><td>12.9 ± 0.2</td><td>65.1 ± 0.8</td><td>9.4 ± 0.2 (9.6)</td><td>1224 ± 146</td><td>6.4 ± 0.2</td></tr><tr><td>Ox:Tet</td><td>95</td><td>1.11 ± 0.01</td><td>13.6 ± 0.4</td><td>64 ± 3</td><td>9.7 ± 0.4 (10.5)</td><td>1420 ± 359</td><td>7.1 ± 0.4</td></tr><tr><td>Ox:DPE</td><td>130</td><td>1.10 ± 0.01</td><td>14.4 ± 0.6</td><td>65 ± 2</td><td>10.3 ± 0.3 (10.9)</td><td>1566 ± 416</td><td>7.2 ± 0.9</td></tr></tbody></table>
<figure><img src="image_4.png" /><figcaption>**FIGURE 2** | Photovoltaic parameters ($V_{oc}$, $J_{sc}$, FF, PCE, $P_{max}$, and $R_{sh}$) as a function of light intensity with a 2700K LED illumination for photovoltaic devices based on spin-coated TPD-3F:FCC-Cl blends processed under inert atmosphere with different solution processing conditions (Ox, Ox:Tet, and Ox:DPE). Dash lines are included to guide the eye.</figcaption></figure>

<figure><img src="image_5.png" /><figcaption>**FIGURE 3** | Plots of short-circuit current density ($J_{sc}$) versus open-circuit voltage ($V_{oc}$) measured for different incident light power density (a) and short-circuit current density ($J_{sc}$) versus incident light power intensity (b) for photovoltaic devices based on TPD-3F:FCC-Cl blends processed by spin-coating under inert atmosphere with different solution processing conditions (Ox, Ox:Tet, and Ox:DPE). These measurements have been performed using a 2700K LED.</figcaption></figure>

resistance values shown above, where the highest shunt resistance for Ox:DPE samples (2343 MΩ·cm²) corresponds to the smallest ideality factor, further confirming the link between reduced trap-mediated pathways and superior device performance [24, 26, 27].

To further support these observations, the dependence of photocurrent on incident light intensity was analyzed as $J \propto P_{in}^S$, and illustrated in Figure 3b. The photocurrent should be scaled linearly with incident power, and a slope (S) close to 1 indicates negligible bimolecular recombination [28]. Across all

formulations, the slopes were consistent, averaging at 0.98, confirming that bimolecular recombination is not a significant limiting factor under indoor illumination. Performance variations among the different formulations can instead be attributed to trap-assisted recombination, with the superior performance of Ox:DPE samples explained by reduced trap-mediated losses, as suggested by the lower ideality factor and higher shunt resistance.

To gain further insight into the disparities in device performance, we analyzed the surface morphology of the blend layers using
<figure><img src="image_6.png" /><figcaption>**FIGURE 4** | AFM images of neat materials (TPD-3F and FCC-Cl) and TPD-3F:FCC-Cl blends processed by spin-coating under inert atmosphere with different solution processing conditions (Ox, Ox:Tet, and Ox:DPE). Scale: 2 µm × 2 µm.</figcaption></figure>

AFM (Figure 4). The results revealed distinct surface characteristics depending on the ink formulation, with roughness mean square values (rms) of 1.3, 5.0, and 3.5 nm for Ox, Ox:Tet, and Ox:DPE, respectively. These variations suggest that the use of solvent additives plays a significant role in shaping the microstructure of the active layer during spin coating. In particular, the increased roughness observed in the Ox:Tet samples suggests less uniform film formation, which could hinder charge transport and contribute to the lower FF and overall efficiency compared to the Ox:DPE devices.

However, these morphological differences alone do not explain the significantly poorer performance of Ox-based devices. To gain further insights, we employed optical microscopy to assess the overall film quality at a larger scale. The Ox-based blend layers exhibited a high density of large morphological defects of varying sizes, as shown in Figure 5 and Figure S5, Supporting Information, potentially degrading the performance and quality of the samples, while the addition of both additives clearly reduces the defect density

and thus increases device performance. The origin of the defect is not clear but we suggest that it is mainly due to residual blend material aggregates in Ox-based inks.

To complement the surface analysis, contact angle measurements were conducted on layers deposited on ITO/ZnO substrates to study the surface composition of blends (Figure S6 and Table S4, Supporting Information). The contact angle analysis of neat materials and Ox-based blend samples revealed that the donor polymer TPD-3F constituted approximately 91% of the surface composition. With comparable contact angle for the Ox: Tet and Ox:DPE solutions, a similar high donor concentration is formed on the top surface of blends. This high donor proportion is favorable for our application and aligns with the requirements for the used inverted device structures.

In addition to surface characterization, we investigated the molecular organization of the blend layers. 2D-GIXRD

<figure><img src="image_7.png" /><figcaption>**FIGURE 5** | Optical microscope images of TPD-3F:FCC-Cl blends spin-coated under inert atmosphere with different solution processing conditions: (a) Ox, (b) Ox:Tet, and (c) Ox:DPE.</figcaption></figure>
<figure><img src="image_8.png" /><figcaption>**FIGURE 6** | 2D-GIXRD in-plane (IP) and out of plane profiles (OPP) of spin-coated TPD-3F:FCC-Cl blends under inert atmosphere with different solution processing conditions (Ox, Ox:Tet, and Ox:DPE).</figcaption></figure>

measurements were performed on spin-coated neat materials (TPD-3F, FCC-Cl in Ox) and TPD-3F:FCC-Cl blends with various formulations (Ox, Ox:Tet, and Ox:DPE). Figure S7, Supporting Information shows 2D-GIXRD patterns while Figure 6 depicts the corresponding 2D-GIXRD in-plane (IP) and out-of-plane (OOP) intensity profiles. Tables S5 and S6, Supporting Information summarize the parameters obtained for neat materials and blends. To identify the contribution of either TPD-3F or FCC-Cl, intensity profiles of both neat thin films are added in Figure S8, Supporting Information. The diffraction indexed (100) in $q_{xy}$ profile of TPD-3F at 0.248 Å highlights a face-on lamellar stacking of this polymer with a lattice constant (d-spacing) of 2.53 nm and a coherent crystallite length (CCL) of 1.3 nm. Furthermore, the observed (010) diffraction peak in $q_z$ profile strengthens this face-on orientation. Similarly, for neat FCC-Cl, an intense and narrow (100) diffraction peak in the $q_{xy}$ profile at 0.372 Å indicates that FCC-Cl films are composed of highly crystalline domains. It is attributed to the face-on lamellar stacking of molecules, with a d-spacing of 1.68 nm and a CCL of 1.83 nm. As with TPD-3F, this predominant face-on orientation is reinforced by a pronounced (010) diffraction peak in the $q_z$ profile. When blended together, the predominant presence of the diffraction peaks (100) in $q_{xy}$ profile show that the crystalline state of both materials is conserved as presented in Figure 6. The Gaussian fit of the (100) peaks for the three formulations shows two population of crystalline organization for all formulations (Figure S9, Supporting Information). The peaks around $q_{xy} = 0.254-0.257$ Å⁻¹ corresponds to TPD-3F, and the peaks at $q_{xy} = 0.365$ Å⁻¹ are attributed to FCC-Cl. Considering the values of d-spacing and CCL, the domains of TPD-3F and FCC-Cl are slightly reduced during the blending process, however, no significant differences are as a function of the solvent additives. A smaller d-spacing for TPD-3F, along with lower CCL values, suggests smaller but denser polymer domains in blend. Conversely, the higher d-spacing of 1.72 nm observed in all formulations, compared to 1.68 nm for neat FCC-Cl films, suggests slightly less dense FCC-Cl domains. Additionally, the decrease in the CCL value indicates a reduction in crystallite size relative to the neat film. Despite the variations observed in the blend, both TPD-3F polymer chains and FCC-Cl small molecules exhibit a well-defined face-on orientation, whether in neat layers or in blends processed with various ink formulations. This orientation is highly favorable for 3D charge carrier transport, facilitating vertical transport relative to the substrate, which corresponds

to the direction involved in the sandwich structure of OPVs. Overall, the 2D-GIXRD measurements reveal that the additives have no significant impact on the molecular organization of the blend layers.

Reproducibility is a key factor in the industrialization of device production and in ensuring consistent functionality, particularly for indoor applications. Devices tested under lower light intensities in indoor conditions are more sensitive to imperfections than those tested under standard AM1.5G conditions. Defects that have minimal impact on performance under standard illumination can cause significant degradation in low-light conditions. This underscores the importance of reliable performance across varying light intensities, which is essential for the practical deployment of indoor photovoltaics. In the present study, the percentage of functional cells is calculated based on devices exhibiting efficiencies greater than 50% of the maximum performance for each formulation, accounting for performance variability. Devices with lower efficiencies are excluded from the analysis. Under standard AM1.5G conditions, the percentage of functional cells is 66%, 83%, and 89% for devices processed with Ox, Ox:Tet, and Ox:DPE formulations, respectively. However, under indoor conditions at 200 Lx, these percentages decrease to 33%, 56%, and 83%, respectively, shown in Figure 7 and Table S7, Supporting Information. This reduction highlights the sensitivity of sample performance under indoor conditions, where defects that do not significantly affect performance at higher illumination levels, can become more pronounced at low-light intensities. Ox-based samples show a greater drop in performance, which can be attributed to the imperfections present in the films, which are detrimental under these conditions. Notably, the most reliable performance is observed for Ox:DPE, which exhibits the highest percentage of functional cells under both illumination conditions. Although a slight decrease in functional cells is observed under low light intensities compared to standard 1-sun performance, Ox:DPE remains the most resilient formulation. This underscores the critical role of DPE in enhancing both the efficiency and reproducibility of devices across varying illumination conditions.

<figure><img src="image_9.png" /><figcaption>**FIGURE 7** | PCE reproducibility of photovoltaic devices based on spin-coated TPD-3F:FCC-Cl blends processed under inert atmosphere with different solution processing conditions (Ox, Ox:Tet, and Ox: DPE) for 1-sun illumination conditions and 2700K LED illumination at 200 Lx.</figcaption></figure>
3 | OPVs of TPD-3:FCC-Cl Blend Processed under Ambient Conditions

After confirming the potential of the TPD-3F:FCC-Cl blend under controlled inert conditions (glovebox processing), we extended our investigation to assess its performance under ambi- ent conditions using doctor blade (DB) coating, a step toward evaluating its industrial relevance. We also explored the fabrica- tion of thicker active layers, as these are more suitable for large- scale manufacturing due to their improved reproducibility and reduced sensitivity to minor defects or processing variations.

Notably, DB coating in ambient air introduced some challenges, particularly for the Ox-based formulation. For thinner films Ox led to rapid solvent evaporation while for thicker films edge defects became apparent. During drying on the heated substrate, the fast evaporation of Ox in the absence of additives caused material migration toward the film edges (Figure 8a). These mor- phological defects were significantly mitigated with the addition of higher-boiling-point solvent additives, Tet and DPE, which enabled slower, more controlled drying. As a result, films proc- essed with Ox:Tet and Ox:DPE formulations exhibited improved uniformity and film quality (Figure 8b,c).

To evaluate how Tet and DPE impact device performance, we fabricated solar cells with blends processed from Ox, Ox:Tet, and Ox:DPE inks at various layer thicknesses. Their current–voltage (J–V) characteristics were measured under AM1.5G illu- mination (Figure 9), with photovoltaic parameters summarized

<figure><img src="image_10.png" /><figcaption>**FIGURE 8** | Photovoltaic devices based on blade-coated TPD-3F: FCC-Cl blends processed under ambient atmosphere with different solu- tion processing conditions (Ox, Ox:Tet, and Ox:DPE) and fabricated with three different thicknesses.</figcaption></figure>

in Table 2. Under standard AM1.5G illumination, all three for- mulations yielded comparable PCEs around 9.5%, with slightly higher values for thinner active layers. Although a modest effi- ciency drop was observed for the 300 nm thick layers, the change remained within statistical variation.

The shunt resistances (R<sub>sh</sub>) extracted from dark J–V curves (Figure 9d–e) are summarized in Table S1 and Figure S3, Supporting Information. DPE-based devices exhibited the high- est shunt resistances, 1294 and 4321 MΩ·cm<sup>2</sup> for thin and thick films, respectively, indicating more effective suppression of leak- age currents. In comparison, devices based on Ox:Tet and Ox showed lower shunt resistance values: 72/376 MΩ·cm<sup>2</sup> for Ox: Tet and just 0.07/916 MΩ·cm<sup>2</sup> for Ox.

These findings suggest that film morphology critically influences shunt path formation, which has limited impact under standard solar illumination but becomes a key factor under low-light (indoor) conditions. Indoor performance results (Tables S8–S12) show that under 5000 Lx, all formulations and thicknesses achieved high efficiencies (~21%). However, at lower light inten- sities (200 Lx), where leakage current plays a more significant role, Ox-based devices exhibited reduced efficiency (~18% for 90–180 nm), with recovery at 280 nm due to improved shunt resistance. In contrast, both Ox:Tet and Ox:DPE devices maintained high efficiencies at 200 Lx, with Ox:DPE formula- tions consistently exceeding 20% across all thicknesses, demon- strating optimal low-light performance and robustness.

The ideality factor was found to range between 1.45 and 1.49 for all blade-coated devices, independent of ink formulation, matching values observed for spin-coated Ox:DPE samples (which also yielded the highest efficiencies; see Figure S10a,c,e, Supporting Information). Exceptions were the 90 and 180 nm Ox-based devices, which had higher ideality factors (1.62 and 1.67), indicating increased trap-assisted recombination. Across all formulations, the slope (S) of the light-intensity dependence remained near 0.98, confirming that bimolecular recombination is not a limiting factor for indoor OPV performance (Figure S10b,d,f).

Furthermore, we investigated the surface morphology and topography using AFM for the blade-coated samples with different formulations and layer thicknesses (thinnest and thickest). Minor variations in rms roughness were observed among the different formulations, with 0.7 nm for Ox, 1 nm for Ox:Tet and 1.7 nm for Ox:DPE (Figure S11, Supporting Information). Notably, similar values were observed for the thicker layers across all formulations. Similarly, the water contact angle showed negligible variation, measuring 105.8° for Ox and 106.6° for both Ox:Tet and Ox:DPE, as shown in Table S13, Supporting Information and Figure S12, Supporting Information. The surface state and composition are therefore preserved across the three solutions.

To investigate the bulk structural characteristics of the blends, 2D-GIXRD measurements were conducted on blade-coated TPD-3F:FCC-Cl layers prepared with different ink formulations (Ox, Ox:Tet, and Ox:DPE). The corresponding 2D-GIXRD patterns as a function of ink formulation are shown in Figure S13, Supporting Information, while the in-plane (IP) and out-of-plane (OOP) intensity profiles are presented in
<figure><img src="image_11.png" /><figcaption>**FIGURE 9** | *J-V* curves under AM1.5G illumination of photovoltaic devices based on TPD-3F:FCC-Cl blends processed by blade-coating under ambient atmosphere with different solution processing conditions for three different film thickness: (a) Ox, (b) Ox:Tet, and (c) Ox:DPE. Dark current curves for the thinnest (c) and thickest (d) TPD-3F:FCC-Cl blends.</figcaption></figure>

<table><caption>**TABLE 2** | Photovoltaic parameters under AM1.5G illumination of photovoltaic devices based on blade-coated TPD-3F:FCC-Cl blends processed under ambient atmosphere with different solution processing conditions (Ox, Ox:Tet and Ox:DPE). Cells area is 0.16 cm².</caption><thead><tr><th>Solution</th><th>Thickness (nm)</th><th>V<sub>oc</sub> (V)</th><th>J<sub>sc</sub> (mA/cm<sup>-2</sup>)</th><th>FF(%)</th><th>PCE(%)</th><th>R<sub>sh</sub> (ohm.cm<sup>2</sup>)</th><th>R<sub>s</sub> (ohm.cm<sup>2</sup>)</th></tr></thead><tbody><tr><td rowspan="3">Ox</td><td>90</td><td>1.11 ± 0.003</td><td>13.6 ± 0.4</td><td>66 ± 1</td><td>9.9 ± 0.4 <b>(10.4)</b></td><td>1204 ± 237</td><td>6.7 ± 0.2</td></tr><tr><td>180</td><td>1.10 ± 0.005</td><td>14.2 ± 0.3</td><td>59 ± 1</td><td>9.1 ± 0.1 <b>(9.3)</b></td><td>985 ± 103</td><td>9.9 ± 0.4</td></tr><tr><td>280</td><td>1.09 ± 0.01</td><td>15.4 ± 0.5</td><td>55 ± 2</td><td>9.1 ± 0.2 <b>(9.3)</b></td><td>718 ± 91</td><td>14 ± 1</td></tr><tr><td rowspan="3">Ox:Tet</td><td>105</td><td>1.10 ± 0.01</td><td>13.4 ± 0.4</td><td>63 ± 4</td><td>9.3 ± 0.8 <b>(10.7)</b></td><td>1243 ± 345</td><td>7.6 ± 0.8</td></tr><tr><td>170</td><td>1.10 ± 0.01</td><td>13.9 ± 0.5</td><td>58 ± 3</td><td>8.8 ± 0.5 <b>(9.6)</b></td><td>924 ± 207</td><td>10 ± 1</td></tr><tr><td>310</td><td>1.10 ± 0.003</td><td>14.3 ± 0.4</td><td>58 ± 2</td><td>9.0 ± 0.3 <b>(9.5)</b></td><td>910 ± 103</td><td>11 ± 1</td></tr><tr><td rowspan="3">Ox:DPE</td><td>120</td><td>1.09 ± 0.01</td><td>13.6 ± 0.2</td><td>62 ± 3</td><td>9.2 ± 0.5 <b>(10.0)</b></td><td>1288 ± 297</td><td>7.9 ± 0.6</td></tr><tr><td>230</td><td>1.09 ± 0.005</td><td>14.5 ± 0.3</td><td>57 ± 1</td><td>9.0 ± 0.2 <b>(9.4)</b></td><td>806 ± 120</td><td>10.8 ± 0.7</td></tr><tr><td>300</td><td>1.08 ± 0.005</td><td>14.8 ± 0.2</td><td>54 ± 2</td><td>8.7 ± 0.3 <b>(9.3)</b></td><td>685 ± 110</td><td>14 ± 2</td></tr></tbody></table>

<figure><img src="image_12.png" /><figcaption>**FIGURE 10** | 2D-GIXRD in-plane (IP) and out of plane profiles (OPP) of blade-coated TPD-3F:FCC-Cl blends processed under ambient atmosphere with different solution processing conditions (Ox, Ox:Tet, and Ox:DPE).</figcaption></figure>

Figure 10, with key data summarized in Tables S14 and S15 (Supporting Information), Similar to the spin-coated TPD-3F: FCC-Cl films, the prominent (100) diffraction peaks in the *q*<sub>xy</sub> profiles confirm that the crystalline ordering of both TPD-3F and FCC-Cl is preserved across all formulations. Gaussian fitting of the (100) peaks reveals two distinct crystalline populations for each ink system: peaks at *q*<sub>xy</sub> = 0.254 Å<sup>-1</sup> correspond to TPD-3F, while peaks at *q*<sub>xy</sub> = 0.365 Å<sup>-1</sup> are attributed to FCC-Cl. Both materials maintain a face-on lamellar stacking orientation, with d-spacings of 2.47 nm for TPD-3F and 1.72 nm for FCC-Cl, consistent across all formulations and identical to those found in spin-coated films using Ox:Tet and Ox:DPE. This further confirms the formation of compact polymer domains alongside slightly more expanded FCC-Cl domains.
<figure><img src="image_13.png" /><figcaption>**FIGURE 11** | PCE reproducibility of photovoltaic devices based on blade-coated TPD-3F:FCC-Cl blends processed under ambient atmosphere with different solution processing conditions (Ox, Ox:Tet, and Ox:DPE) for three different blend thicknesses under 1-sun standard illumination conditions and 2700K LED illumination at 200 Lx.</figcaption></figure>

The most notable impact of the DB process is observed in the calculated CCL values. The CCL of TPD-3F domains slightly decreases with the use of additives, from 1.05 nm in Ox-based films to 1.03 nm and 0.98 nm in Ox:Tet and Ox:DPE formulations, respectively. Conversely, FCC-Cl domains show enhanced crystallinity with additives, with CCL values of 1.70 nm for Tet and 1.78 nm for DPE, approaching the value observed in neat FCC-Cl films (1.83 nm). This expansion of FCC-Cl domains likely induces partial separation of polymer chains due to material intermixing. Overall, blade-coated layers exhibit a consistent face-on orientation for both TPD-3F and FCC-Cl in all formulations, which is favorable for vertical charge transport in OPV devices.

In addition, sample reproducibility was assessed, as shown in Figure 11 and detailed in Table S16, Supporting Information. Ox-based thin films exhibited poor reproducibility, with values around 17% at 90 nm. However, increasing the layer thickness significantly improved reproducibility, reaching ~67% at 280 nm. Ox:Tet samples showed more stable reproducibility, increasing from 39% at 105 nm to 56% at 310 nm. Notably, DPE-based samples demonstrated the highest reproducibility, ranging from 67% at 120 nm to an impressive 92% at 300 nm. These findings underscore the enhanced processability of DPE under ambient conditions, offering a clear advantage over Tet and even over inert processing conditions.

## 4 | Conclusion

In conclusion, this study provides a thorough examination of the TPD-3F: FCC-Cl donor-acceptor blend for indoor

energy-harvesting applications, emphasizing processing under industrially relevant conditions. The effects of solvent additives, specifically tetralin and DPE, were assessed under both inert and ambient environments using spin coating and doctor-blading techniques. The study demonstrates the strong potential of the TPD-3F:FCC-Cl blend for sustainable and high-efficiency indoor OPVs, particularly when processed using non-halogenated solvents and scalable techniques such as blade coating under ambient conditions. The use of DPE as a greener additive significantly improves film uniformity, device reproducibility, and performance stability across varying light intensities and layer thicknesses. Structural analysis via 2D-GIXRD confirms favorable face-on orientation and enhanced crystallinity, particularly for FCC-Cl domains, with DPE-based formulations yielding the most uniform and processable films. Reproducibility metrics further reinforce the superiority of DPE over traditional additives like tetralin, highlighting its promise for industrial-scale indoor OPV applications.

# 5 | Experimental Section

## 5.1 | Materials

Glass-patterned ITO substrates (size 25 mm × 25 mm) with 15 Ω/sq resistance were purchased from Lumtec, Taiwan. ZnO nanoparticle dispersion (N11 at 2.5%) was purchased from Avantama. Molybdenum (VI) oxide powder (MoO₃ purity 99.97%) was purchased from Sigma-Aldrich (Merck) and Silver (Ag, purity 99.99%) drops are from Kurt J. Lesker. Oxylene (Ox) (C₆H₄(CH₃)₂, anhydrous 97%), 1,2,3,4-tetrahydronaphthalene (Tet)
(analytical standard), diphenyl ether for synthesis (DPE), and anhydrous 2-propanol (99.5%) were all purchased and used as received from Sigma-Aldrich (Merck). TPD-3F and FCC-Cl were purchased from 1-Materials. All commercial materials were used as received without purification and kept under nitrogen atmosphere.

## 5.2 | Ink Formulation

Three different ink formulations based on the TPD-3F:FCC-Cl blend were prepared, using the same Donor:Acceptor ratio of 1:1.5 and total concentration of 20 mg/mL. Solutions were dissolved for the different formulations in: 100% oxylene, 85% oxylene + 15% tetralin, and 85% oxylene + 15% DPE (% by volume). Solutions were stirred at 80°C overnight for a minimum of 15 h, then cooled to ambient temperature prior to deposition. Materials were weighed, and the inks were mixed, agitated, heated, and prepared inside the glovebox.

## 5.3 | Device Fabrication

OPVs were fabricated in inverted structure ITO/ZnO/BHJ/MoO3/Ag. The glass-ITO substrates were thoroughly cleaned with a cloth dampened in isopropanol, followed by sonication in isopropanol for 30 min and UV ozone treatment (80°C/15 min). ZnO (1% N11 from Avantama, diluted in isopropanol) was spin-coated dynamically under a fume hood at ambient conditions onto the pre-cleaned ITO glass substrates at 5000 rpm for 1 min to a thickness of 15–20 nm and transferred to the glovebox for annealing on a hot plate at 120°C for 10 min. The active layer was then deposited by static spin coating in the glovebox or by blade coating under ambient conditions. Details of all the active layers for both deposition techniques are summarized below. The HTL (3 nm of MoO3) and upper electrode (100 nm Ag) were thermally evaporated inside the glovebox under a pressure of $2 \times 10^{-6}$ mbar, using a designated shadow mask to achieve precise patterning (0.16 $cm^2$ used as active layer surface).

## 5.4 | Spin-Coating Process

The TPD-3F: FCC-Cl active layer was statically spin-coated inside the glovebox from 20 mg/mL using 150 µL of solutions at 1000 rpm for 1 min, resulting in layers of 95, 95, and 130 nm for Ox, Ox:Tet, and Ox:DPE solutions, respectively and annealed at 120°C on a hot plate for 5 min.

## 5.5 | Blade-Coating Process

The TPD-3F: FCC-Cl active layer was statically blade coated in air and at ambient temperature from 20 mg/mL solutions with different sweep speeds. For the Ox solution, the sweep speeds used were 8, 20, and 35 mm/s, with active layer thicknesses of 90, 180, and 280 nm, respectively. For Ox:Tet, the sweep speeds were 10, 22, and 32 mm/s for resulting in thicknesses of 105, 170, and 310 nm, respectively. For Ox:DPE, using sweep speeds of 8, 20, and 30 mm/s active layer thicknesses of 120, 230, and 300 nm, respectively were measured. The gap was fixed at 60 µm and the ink volume used was 30 µL for all formulations.

Active layer films were annealed in air just after deposition at 120°C for 5 min. Samples were transferred to the glovebox for thermal evaporation.

## 5.6 | Outdoor J–V Characterization

The current density–voltage curves of the devices under an AM1.5G light solar simulator (Newport Sol3A Class AAA) were recorded using a Keithley 238 source meter unit inside the glovebox. The illumination intensity of the light source was calibrated to 100 mW/cm² using a standard silicon solar cell (Newport Company, Oriel no. 94043A) calibrated by the National Renewable Energy Laboratory (NREL).

## 5.7 | Indoor J–V Characterization

Indoor J–V measurements at several illuminance conditions were done using a home-made indoor simulator black box situated inside the glovebox for sample characterization in inert atmosphere. The set-up consists in a black-box used to avoid environment noise light contributions to the measurements and a home-made designed power supply unit for illuminance control of the LED cards. It allows flexible characterization in indoor conditions using different color temperature LED sources that can be installed/disassembled in the lamp holder dissipator. By means of the power supply unit, it is possible to program different indoor illuminance levels by intensity control of the different LED cards and synchronize the measurements using a Keithley 238 source meter unit. The working distance LED sample is 150 mm and illuminance control is done by adjusting the current for the most common used illuminance levels (200, 500, 1000, 2000, 5000 Lx), which have been previously calibrated at the stated distance for the several LED sources using a Black-Comet CXR-SR calibrated spectrometer from StellarNet Inc. LED sources used in the setup are white LED lights OLSON150 4+ PowerStar Whites with references ILH-OW04-HWWHSC211-WIR20 and ILH-OW04-NUWHSC211-WIR200 for 2700 K warm and 4000 K neutral white colors, respectively. Detailed parameters are available in image Figure S14 and Table S17, Supporting Information.

## 5.8 | Characterization of Organic Films

The absorbance of the active layer films was measured via a UV-Vis-near infrared Spectrophotometer Cary 5000. Film thicknesses were measured using a stylus profilometer (Bruker DEKTAK XT) with 1 mg of force on the probing tip. The surface morphology of the blend layers was investigated via AFM (NTEGRA from NT-MIDT) in semi-contact mode using the sili-con tips (MikroMash) with a theoretical resonant frequency of 150 kHz and a force constant of $5.4 \ N.m^{-1}$ at room temperature. Contact water angle (CWA) measurements were performed with an optical contact angle (OCA) series 15EC with a high-resolution USB camera and sample positioning from DataPhysics Instrument GmbH Company in a room with a controlled temperature around 20°C.

Thin films were further analyzed with high-brightness synchrotron radiation at BL19B2 in SPring-8 (Sayo in Japan). GWAXS
(Grazing-Incidence Wide-Angle X-ray Scattering) measurements were performed using a high-sensitive 2D X-ray detector (PILATUS 300K). The incident angle and wavelength of X-rays were 0.13° and 0.100 nm, respectively. The crystal coherence length (CCL) values were extracted via the Scherrer equation:

$$ \tau = \frac{K\lambda}{\beta \cos \theta} \qquad (1) $$

where τ is the ordered (crystalline) domains mean size here, defined as CCL, K is a constant (dimensionless shape factor) closed to unity. The shape factor is typically equal to 0.9, λ is the wavelength of the X-ray, β is the full width at half maximum (FWHM) of the diffraction peak in radians after subtracting the instrumental line broadening and θ is the Bragg angle. From an analytical standpoint, FWHM is used to determine the length scale over which ordered regions (e.g., crystallites) diffract or scatter coherently, as described by the Scherrer equation.

## Acknowledgments

J.A., O.M., C.V.-A., C.M.R., D.F., H.A., and S.B.D. gratefully acknowledge the support of the CNRS and Dracula Technologies through a collaborative research agreement (Contract No. [225847]) and Agence Nationale de la Recherche (ANR) through the LabCom IOPV-Lab (Contact No. ANR-21-LCV2-0001-01). Additionally, J.A., C.M.R. and A.K. gratefully acknowledge the support of the French Ministry of Higher Education and Research and the National Association for Research and Technology (ANRT) through a CIFRE fellowship (No. 2020/0978) in collaboration with Dracula Technologies. C.V.-A., J.A., and O.M. thank F. Jandard and S. Lavandier from CINAM (Electronics and instrumentation division) for their assistance in building the indoor measurement facilities and developing the acquisition software. The synchrotron radiation experiments were performed at BL19B2 in Spring-8 with the approval of Japan Synchrotron Radiation Research Institute (JASRI) (Proposal No. 2021A2031). C.V.-A. expresses her special thanks to Prof. Noriyuki Yoshimoto for setting up the collaboration for GWAXS experiments.

## Conflicts of Interest

The authors declare no conflicts of interest.

## Data Availability Statement

The data that support the findings of this study are available in the supplementary material of this article.

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## Supporting Information

Additional supporting information can be found online in the Supporting Information section. **Supporting Fig. 1:** Normalized absorption spectra of spin-coated TPD-3F:FCC-Cl layers processed with different solution processing conditions Ox (Black), Ox:Tet (Red), and Ox:DPE (Blue), along with setup LED emission spectra at 2700K (dotted orange) and 4000 K (dotted blue) measured at 1000 lux. **Supporting Fig. S2:** Distribution of dark shunt resistance (Rsh) values for all functional devices based on spin-coated TPD-3F:FCC-Cl blend films processed under inert atmosphere with different solution processing conditions (Ox, Ox:Tet and Ox:DPE). **Supporting Fig. 3:** Distribution of dark shunt resistance (Rsh) values for functional devices based on blade-coated TPD-3F:FCC-Cl blend films processed under ambient atmosphere with different solution processing conditions (Ox, Ox:Tet and Ox:DPE). Distributions are shown separately for (a) the thinnest and (b) thickest films obtained within each solution set. **Supporting Fig. 4:** (a) J-V curves of photovoltaic devices based on spin-coated TPD-3F:FCC-Cl blends processed under inert atmosphere with different solution processing conditions (Ox, Ox:Tet and Ox:DPE) under 2700K illumination at 1000 Lux intensity. J-V curves of spin-coated TPD-3F:FCC-Cl blends processed in Ox (b), in Ox:Tet (c) and Ox: DPE (d) DPE under 2700K at different intensities from 200 to 5000 Lux. Cell area is 0.16 cm². **Supporting Fig. 5:** Optical microscope images showing some particles/aggregates for TPD-3F:FCC-Cl blends spin-coated under inert atmosphere from Ox solution: (a) comet effect and (b) aggregates under electrode. **Supporting Fig. 5:** Optical microscope images showing some particles/aggregates for TPD-3F:FCC-Cl blends spin-coated under inert atmosphere from Ox solution: (a) comet effect and (b) aggregates under electrode. **Supporting Fig. 6:** Water contact angles of spin-coated TPD-3F and FCC-Cl neat films, as well as spin-coated TPD-3F:FCC-Cl blends with different solution processing conditions (Ox, Ox:Tet and Ox:DPE). Films were deposited on ITO/ZnO. An average from at least 3 measurements were done. **Supporting Fig. 7:** 2D-GIXRD patterns of spin coated TPD-3F, FCC-Cl neat layers from Ox solution and TPD-3F:FCC-Cl blends with different solution processing conditions (Ox, Ox:Tet and Ox:DPE). **Supporting Fig. 8:** 2D-GIXRD in-plane (IP) and out of plane profiles (OPP) of spin-coated TPD-3F and FCC-Cl layers processed by spin-coated under inert atmosphere from Ox solution. **Supporting Fig. 9:** Zoom with Gaussian fit of the (100) peak of spin coated TPD-3F:FCC-Cl blends processed by spin-coated under inert atmosphere from Ox solution. **Supporting Fig. 10:** Plots of photocurrent density (Jsc) versus effective voltage ( Voc) and versus light intensity of TPD-3F:FCC-Cl blends processed by blade-coated under ambient atmosphere with different solution processing conditions (Ox, Ox:Tet and Ox: DPE) under 2700K illumination. **Supporting Fig. 11:** AFM images of TPD-3F:FCC-Cl blends processed by blade-coated under ambient atmosphere with different solution processing conditions (Ox, Ox:Tet and Ox: DPE). Scale: 2 µm × 2 µm. **Supporting Fig. 12:** Water contact angles of blade-coated TPD-3F:FCC-Cl blends with different solution processing conditions (Ox, Ox:Tet and Ox:DPE). Films were deposited on ITO/ZnO.

An average from at least 3 measurements were done. **Supporting Fig. 13:** 2D-GIXRD patterns of blade-coated TPD-3F:FCC-Cl blends with different solution processing conditions (Ox, Ox:Tet and Ox:DPE). **Supporting Fig. 14:** Irradiance of LED sources used for indoor setup: (a) 2700K and (b) 4000K. **Supporting Table 1:** Shunt resistance (Rsh) values extracted from dark current–voltage (J–V) measurements of TPD-3F: FCC-Cl blend films processed via spin coating and blade coating under inert and ambient conditions. Rsh values are reported as a function of film thickness for three different solution processing conditions: Ox, Ox:Tet, and Ox:DPE. Mean values, standard deviations, and maximum Rsh values are provided for each processing condition. Calculations were performed for the thinnest and thickest layers in blade-coated blends, and for a representative thin layer in spin-coated blends. **Supporting Table 2:** Average device parameters of spin-coated TPD-3F:FCC-Cl blends processed under inert atmosphere with different solution processing conditions (Ox, Ox:Tet and Ox:DPE) under indoor conditions at 2700K at different illuminations (200 to 5000 lux). Cells area is 0.16 cm². **Supporting Table 3:** Average device parameters of spin-coated TPD-3F:FCC-Cl blends processed under inert atmosphere with different solution processing conditions (Ox, Ox:Tet and Ox:DPE) under indoor conditions at 4000K at different illuminations (200 to 5000 lux). Cells area is 0.16 cm². **Supporting Table 4:** Water contact angles and calculations of materials fractions at the surface for spin-coated TPD-3F:FCC-Cl blends with different solution processing conditions (Ox, Ox:Tet and Ox:DPE). **Supporting Table 5:** In-plane (100) XRD data of neat materials (TPD-3F and FCC-Cl) and TPD-3F:FCC-Cl blends processed by spin-coating under inter atmosphere with different solution processing conditions (Ox, Ox:Tet and Ox:DPE). **Supporting Table 7:** Reproducibility for spin-coated TPD-3F:FCC-Cl blends processed under inert atmosphere versus solution processing conditions (Ox, Ox:Tet and Ox:DPE). Statistical analysis of functional cells under AM1.5G illumination conditions and 2700K at 200 lux versus number of processed cells. **Supporting Table 8:** Performance of blade-coated TPD-3F:FCC-Cl blends processed form Ox solution under indoor illumination from 200 to 5000 lux at 2700K color temperature. Cells area is 0.16 cm². **Supporting Table 9:** Performance of blade-coated TPD-3F: FCC-Cl blends processed form Ox:Tet solution under indoor illumination from 200 to 5000 lux at 2700K color temperature. Cells area is 0.16 cm². **Supporting Table 10:** Performance of blade-coated TPD-3F:FCC-Cl blends processed form Ox:DPE solution under indoor illumination from 200 to 5000 lux at 2700K color temperature. Cells area is 0.16 cm². **Supporting Table 11:** Performance of blade-coated TPD-3F:FCC-Cl blends processed form Ox:Tet solution under indoor illumination from 200 to 5000 lux at 4000K color temperature. Cells area is 0.16 cm². **Supporting Table 12:** Performance of blade-coated TPD-3F:FCC-Cl blends processed form Ox:DPE solution under indoor illumination from 200 to 5000 lux at 4000K color temperature. Cells area is 0.16 cm². **Supporting Table 13:** Water contact angles of blade-coated TPD-3F: FCC-Cl blends versus solution processing conditions (Ox, Ox:Tet and Ox:DPE). **Supporting Table 14:** In-plane (100) XRD data of TPD-3F: FCC-Cl blends processed by blade-coating under ambient atmosphere with different solution processing conditions (Ox, Ox:Tet and Ox: DPE). **Supporting Table 15:** Out-of-plane (010) XRD data of TPD-3F: FCC-Cl blends processed by blade-coating under ambient atmosphere with different solution processing conditions (Ox, Ox:Tet and Ox: DPE). **Supporting Table 16:** Reproducibility for blade-coated TPD-3F: FCC-Cl blends processed under ambient atmosphere versus solution processing conditions (Ox, Ox:Tet and Ox:DPE) as function of film thickness. Statistical analysis of functional cells under AM1.5G illumination conditions and 2700K at 200 lux versus number of processed cells. **Supporting Table 17:** Table detailing the different values of LED characterization.