The PCEs of small-area single junction OSCs have reached over 19%, providing an essential foundation for scaling up. [16][17][18] However, these devices with an effective area smaller than 0.1 cm 2 are usually fabricated by the spin-coating method on glassindium tin oxide (ITO) substrates, which limits the further upscale continuous production due to the associated uneven linear speed. Large-area coating methods, such as spray coating, [16] blade coating, [17][18][19] slot-die coating, [20][21][22] inkjet printing, [23] etc., are widely used in the scalable fabrication of large-area OSCs. Due to its advantages of easy operation, low material waste, and high throughput, the slot-die coating process is considered one of the most promising approaches in the field of largearea OSCs and has the potential for further roll-to-roll (R2R) production. [24][25][26][27][28] Recently, many studies revealed that the solvent drying process in the slot-die coating is much slower than that in spin coating, leading to a significant change in the nanoscale morphology of the photoactive layers. [29] Various efforts have been devoted to optimizing the slot-die coating methodology for fabricating high-efficiency OSCs. Early in 2014, Zhan et al. focused on the drying mechanism in the spin-coating and roll-coated methods by comparing the amount of additive, demonstrating the importance of the individual optimization approach in the large-area coating process. [30] By synergistic optimization of slot-die coating conditions, our group successfully acquired high-efficiency flexible devices, which maintain over 98% PCE of the small-area rigid devices. [31] Besides the coating condition optimization, tremendous efforts have been made to investigate the aggregation during the coating process. Ma et al. revealed that processing conditions could affect the phase-separation kinetics of donors and acceptors in the active layer, such as coating temperature and solution temperature. [32,33] Molecular aggregation ability significantly influences film formation kinetics of the active layer, while its influence on slot-die coating fabrication has seldom been investigated. Recently, we developed two acceptors with low reorganization energy, i.e., Qx-1 and Qx-2, and the spin-coated small-area devices of PM6:Qx-1 and PM6:Qx-2 fabricated using chloroform showed similar device performance (≈18%) due to their similar molecular structure. [34] Slot-die coating is recognized as the most compatible method for the roll-toroll (R2R) processing of large-area flexible organic solar cells (OSCs). However, the photovoltaic performance of large-area flexible OSC lags significantly behind that of traditional spin-coating devices. In this work, two acceptors, Qx-1 and Qx-2, show quite different film-formation kinetics in the slot-die coating process. In situ absorption spectroscopy indicates that the excessive crystallinity of Qx-2 provides early phase separation and early aggregation, resulting in oversized crystal domains. Consequently, the PM6:Qx-1-based 1 cm 2 flex...
The commercialization of organic solar cells (OSCs) requires the use of roll‐to‐roll coating technology. However, it is generally believed that all‐small‐molecule (ASM) systems cannot form high‐quality films in most film‐fabrication technologies except for spin coating, mainly due to their strong crystallinity and low solution viscosity. Herein, it is found that the small molecule donor and acceptor system with strong intermolecular interaction can weaken the molecular self‐aggregation during film formation. As a result, all‐small‐molecule organic solar cells (ASM‐OSCs) are successfully fabricated using the green solvent tetrahydrofuran via spin coating as well as slot‐die coating technology. Under the optimal conditions, the devices achieve power conversion efficiency (PCE) of 14.05% and 13.41% prepared by spin coating and slot‐die coating, respectively. Moreover, a large‐area device with an area of 1 cm2 achieve a PCE of 10.65% by slot‐die coating. The study of the device performance and the active layer morphology reveal a unique film optimization mechanism in ASM‐OSCs. In the slot‐die coating process, a high‐quality film is formed due to the significantly suppressed crystallinity of the small molecule donor; with further thermal annealing, the crystallization‐induced phase separation enables an optimized morphology. This study proves that high‐performance ASM‐OSCs can be fabricated by the industrial‐compatible method.
Photovoltaic windows with easy installation for the power supply of household appliances have long been a desire of energy researchers. However, due to the lack of top electrodes that offer both high transparency and low sheet resistance, the development of high transparency photovoltaic windows for indoor lighting scenarios has lagged significantly behind photovoltaic windows where privacy issues are involved. Addressing this issue, in this work we develop a solution processable transparent top electrode using sandwich structure silver nanowires, realizing high transparency in semi‐transparent organic solar cells. The wettability and conducting properties of the electrode are improved by a modified hole‐transport layer named HP. The semi‐transparent solar cell exhibits good see‐through properties at a high average visible transmittance of 50.8%, with power conversion efficiency of 7.34%, and light utilization efficiency of 3.73%, which is the highest without optical modulations. Moreover, flexible devices based on the above‐mentioned architecture also show excellent mechanical tolerance compared with Ag electrode counterparts, which retains 94.5% of their original efficiency after 1500 bending cycles. This work provides a valuable approach for fabricating solution processed high transparency organic solar cells, which is essential in future applications in building integrated photovoltaics.This article is protected by copyright. All rights reserved
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