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The ability of organic photovoltaics (OPVs) to be deposited on flexible substrates by roll-to-roll (R2R) processes is highly attractive for rapid mass production. Many research teams have demonstrated the great potential of flexible OPVs. However, the fabrication of R2R-coated OPVs is quite limited. There is still a performance gap between the R2R flexible OPVs and the rigid OPVs. In this study, we demonstrate the promising photovoltaic characteristics of flexible OPVs fabricated from blends of low bandgap polymer poly[(2,6-(4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)-benzo[1,2-b:4,5-b′]dithiophene))-alt-(5,5-(1′,3′-di-2-thienyl-5′,7′-bis(2-ethylhexyl)benzo[1′,2′-c:4′,5′-c′]dithiophene-4,8-dione)] (PBDB-T) and non-fullerene 3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)-indanone))-5,5,11,11-tetrakis(4-hexylphenyl)-dithieno[2,3-d:2′,3′-d′]-s-indaceno[1,2-b:5,6-b′]dithiophene (ITIC). We successfully R2R slot-die coated the flexible OPVs with high power conversion efficiency (PCE) of over 8.9% under irradiation of simulated sunlight. Our results indicate that the processing parameters significantly affect the PCE of R2R flexible OPVs. By adjusting the amount of solvent additive and processing temperature, as well as optimizing thermal annealing conditions, the high PCE of R2R slot-die coated OPVs can be obtained. These results provide significant insights into the fundamentals of highly efficient OPVs for the R2R slot-die coating process.

The ability of organic photovoltaics (OPVs) to be deposited on flexible substrates by roll-to-roll (R2R) processes is highly attractive for rapid mass production. Many research teams have demonstrated the great potential of flexible OPVs. However, the fabrication of R2R-coated OPVs is quite limited. There is still a performance gap between the R2R flexible OPVs and the rigid OPVs. In this study, we demonstrate the promising photovoltaic characteristics of flexible OPVs fabricated from blends of low bandgap polymer poly[(2,6-(4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)-benzo[1,2-b:4,5-b′]dithiophene))-alt-(5,5-(1′,3′-di-2-thienyl-5′,7′-bis(2-ethylhexyl)benzo[1′,2′-c:4′,5′-c′]dithiophene-4,8-dione)] (PBDB-T) and non-fullerene 3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)-indanone))-5,5,11,11-tetrakis(4-hexylphenyl)-dithieno[2,3-d:2′,3′-d′]-s-indaceno[1,2-b:5,6-b′]dithiophene (ITIC). We successfully R2R slot-die coated the flexible OPVs with high power conversion efficiency (PCE) of over 8.9% under irradiation of simulated sunlight. Our results indicate that the processing parameters significantly affect the PCE of R2R flexible OPVs. By adjusting the amount of solvent additive and processing temperature, as well as optimizing thermal annealing conditions, the high PCE of R2R slot-die coated OPVs can be obtained. These results provide significant insights into the fundamentals of highly efficient OPVs for the R2R slot-die coating process. [ABSTRACT FROM AUTHOR]

• Halogen-free and ambient slot-die coating of the small-molecule organic solar cell and module. • Thermal annealing for mass production, good photo-stability and indoor lighting performance. • Tunable BHJ film morphologies of sheet-to-sheet and flexible roll-to-roll slot-die coatings. • Efficiency of S2S and flexible R2R slot-died SMOSC achieve 7.6% and 7.3%, respectively, • Characteristic, structural and systematic study correlating processing and performance. The upscale fabrication of the inverted small-molecule organic solar cell (SMOSC) from spin coating to large-area slot-die coating using halogen-free solvent under the ambient air environment is developed. This work successfully adopts thermal annealing treatment to tune the bulk heterojunction (BHJ) structure for two advantages of compatibility to mass production and good photo-stability. By tuning the respective optimum film structure, the power conversion efficiency (PCE) values under AM 1.5G light and indoor light (T5 lamp with 500 lx) illuminations for the ambient spin-coated device achieve 8.5% and 13.26%, respectively. The photo-bleaching and light-soaking tests under the AM 1.5G illumination show that the photo-stability of the thermally-annealed DRCN5T:PC 71 BM device is much better than PTB7-Th:PC 71 BM device. The tunable BHJ film morphologies of large-area ITO/glass-based sheet-to-sheet (S2S) and flexible roll-to-roll (R2R) slot-die coatings of DRCN5T:PC 71 BM SMOSCs are based on different dry-film formation and crystallization mechanisms. The structural control during the drying-film process for S2S and R2R coatings is a critical key to determine the optimum performance. The PCEs of the ITO/glass-based and flexible ITO/PET-based SMOSCs achieve 7.6% and 7.3%, respectively. The PCE of the ambient flexible R2R slot-die-coated SMOSC using halogen-free solvent is much higher than that of the currently flexible R2R coated SMOSCs. The PCEs of S2S slot-die-coated cell device of 1 × 5 cm2 and module achieve 5.1%. We conduct a characteristic, structural and systematic study of how to scale-up SMOSC via slot-die coatings, demonstrating the relationship among processing control, performance and structure for different coatings. [ABSTRACT FROM AUTHOR]

The manufacture of ambient roll-to-roll (R2R) slot-die-coated organic photovoltaic (OPV) is the basis toward commercialization of OPV. The low-cost large-area encapsulation technique of stability improvement of flexible OPV module is under-investigated. The related reports on flexible encapsulation up-scaled from cell were limited. The present study develops an effective and easy encapsulation method and architecture design based on the inverted structure of ambient R2R slot-die-coated PET/ITO/ZnO/active layer/hole transport layer (HTL)/Ag. All module areas are greater than 48 cm2. The P3HT:PCBM and PV2000:PC 71 BM adopted as active layers have the performance conversion efficiencies of modules of 1–2.2% and 4.2%, respectively. The thermally-deposited MoO 3 and slot-die-coated PEDOT:PSS HTLs are used to compare the effect of HTL on T 80 lifetime of the large-area flexible R2R module under the accelerated test. The accelerated stability tests regarding to different encapsulation architectures, including damp-heat and light soaking stresses, were conducted. The intrinsic and extrinsic degradation effects are analyzed. We develop the simple encapsulation design effectively suppressing the lateral ingress of oxygen and moisture. The T 80 lifetime of P3HT:PCBM-based module can be improved to be 1500 h under the damp-heat test (65 °C/65% RH). The T 80 lifetime of PV2000:PC 71 BM-based module can last for 7000 h under the dark and ambient environment (30 °C/50 ± 20% RH). [ABSTRACT FROM AUTHOR]

This work develops a combinational use of solvent additive and in-line drying oven on the flexible organic photovoltaics to improve large-area roll-to-roll (R2R) slot-die coating process. Herein, addition of 1,8-diiodooctane (DIO) in the photoactive layer is conducted to yield a performance of 3.05% based on the blending of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C61-butyric acid methyl ester (PC61BM), and a very promising device performance of 7.32% based on the blending of poly[[4,8-bis[(2-ethylhexyl)oxy] benzo[1,2-b:4,5-b'] dithiophene-2,6-diyl] [3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl]] (PTB7) and [6,6]-phenyl C71-butyric acid methyl ester (PC71BM). Based on this R2R slot-die coating approach for various polymers, we demonstrate the high-performance result with respect to the up-scaling from small high-PCE cell to large-area module. This present study provides a route for fabricating a low-cost, large-area, and environmental-friendly flexible organic photovoltaics. [ABSTRACT FROM AUTHOR]

Graphical abstract Feasible commercial process to manufacture highly efficient perovskite solar cells. Highlights • A rapid and nitrogen-free process for the fabrication of planar inverted structured perovskite solar cells (PSCs). • An alternative post-annealed method was developed by near-infrared (NIR) radiation to traditional heating oven. The annealed time can be shorten from 1500 s to 30 s by NIR irradiation. • The crystalline and nano-morphological structures of perovskite layers correlated to thermal and NIR annealing effects were revealed by the grazing-incidence wide-angle and small-angle X-ray scattering (GIWAXS and GISAXS). • Performance of sheet-to-sheet slot-die coated PSCs fabricated under ambient air can be achieved to 12.3%. Abstract A nitrogen-free and slot-die coating fabrication of perovskite solar cells combined with NIR annealing. We develop a fabrication approach of planar inverted structured perovskite solar cell (PSC) in ambient condition with a PCE of 12.4% as compared to that (13.3%) of PSC fabricated in glove box filled with nitrogen. In addition, we demonstrate an alternative post-annealed method by near-infrared (NIR) radiation to traditional heating method by oven. The annealed time by NIR can be shortened from 1500 s to 30 s and the device performance over 10% can be achieved. The present work investigates the NIR effect for different layers in the two-step processing on the cell performance. The grazing-incidence wide-angle and small-angle X-ray scattering (GIWAXS and GISAXS) techniques for the perovskite layers are performed to reveal the crystalline and nano-morphological structures of perovskite layers correlated to thermal and NIR annealing effects. Based on this approach under ambient air, we scale up to the large-area fabrication using the slot-die coating. The performance of slot-die coated PSC can achieve to 12.3%. The critical step is the control of PbI 2 layer thickness. We also applied the NIR radiation to the slot-die coated PSC and the PCE of 11.4% can be achieved. Our study paves a facile way to rapid manufacture and mass production of perovskite solar cells. [ABSTRACT FROM AUTHOR]

In this study, the organic photovoltaics (OPVs) with bulk heterojunction (BHJ) structure based on the active layer of PTB7:PC 71 BM and fabricated by sheet-to-sheet slot-die coating process are prepared to evaluate the uniformity and process stability of the active layer on cell performance. Various solvent additives are mixed in the host solvent o-xylene for improving the performance of low band-gap based polymer system. The solvent additives as recipe will influence the drying rate as well as the nano-BHJ morphology of the active layer. The residual solvent left in the dried film plays an important role in determining the uniformity and performance of organic photovoltaics. Thus, we comparatively investigate the correlation between recipes using solvent additives and different substrate temperature on sheet-to-sheet (S2S) system. OPV with active areas of range from 1 × 0.3, 1 × 1, 1 × 2 to 1 × 4 cm2 are fabricated to verify the performance of the scale-up devices. The temperature-independent feature of substrate is demonstrated for the recipe of 1.5 vol% 1,8-diiodooctane (DIO) plus 1.5 vol% 1-chloronaphthalene (CN). Less performance loss of 2.7% is shown at the active area of 1 × 4 cm2 compared to that of 16.1% for the recipe of 3 vol% DIO. The results will facilitate the scalable commercialization due to several merits of broad process window of S2S slot-die coating process, high film uniformity and high reproducibility between batches, and high power conversion efficiency. • Slot-die coating of organic solar cell and module with improved uniformity and process stability. • Add solvent additives in active layer to control the uniformity of slot-die films. • Tune the substrate temperature to control the BHJ film morphology. • Large-area devices and module with low power conversion efficiency loss. [ABSTRACT FROM AUTHOR]

We systematically investigated the thermal effects of drying process as well as thermal annealing on morphology and performance of inverted polymer solar cells (PSCs) fabricated by roll-to-roll (R2R) slot-die coating. Power conversion efficiency (PCE) of PSCs layer is strongly influenced by bulk heterojunction (BHJ) active layer. Compared to the conventional annealing process, we demonstrate that the drying process for transforming the wet active layer into solid-state film (an early polymer crystallization step) in the R2R process is a critical control of morphological evolution to the desired structure. We have demonstrated that a significant improvement in performance of inverted PSCs can be achieved by tuning the parameters in the drying process prior to the annealing process. This study provides the mechanistic understanding of how the drying and annealing processes affect the morphological evolution regarding to the crystallinity, BHJ structure and interface between layers. Moreover, with respect to environmental concerns, halogen-free are carried out as an alternative solvent to halogenated solvents. We successfully incorporate halogen-free solvent, o-xylene, with an elevated drying temperature for improving the performance of R2R slot-die coated inverted solar cells. [ABSTRACT FROM AUTHOR]

For attaining the commercialization, the large-area roll-to-roll (R2R) slot-die-coated inverted polymer solar cells (PSCs) would be promising. The electron transport layer (ETL) plays an important role in scale-up development from small PSCs. In this work, the active layer comprising poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C 61 -butyric acid methyl ester (PCBM) and sol–gel zinc oxide (ZnO) ETL were slot-die coated on flexible PET/ITO substrate as reference based on the R2R process. Aluminum-doped ZnO (AZO) instead of ZnO was also adopted. For further improving the performance of large-area PSC, we used polyethylenimine ethoxylated (PEIE) material to tailor the nanostructure of ZnO and AZO ETLs for reducing the surface traps on ETLs using two approaches: (1) ZnO/PEIE bilayer formed by sequential deposition and (2) ZnO:PEIE hybrid composite as ETLs. The present work would demonstrate the optimum material (fabrication) parameters and how the performance of the R2R large-area slot-die coated PSC can be improved by modifying the ZnO- and AZO-based ETL structures. We also perform the various measurements and structural characterization to understand the relationship among R2R slot-die coating process, charge transport properties, film structure and photovoltaic performance as increasing the device areas from 1×0.3 cm 2 (power conversion efficiency: 2.69%) to 1×1 cm 2 . [ABSTRACT FROM AUTHOR]