Thiophene is widely used in organic photovoltaics due to its excellent charge transport properties, simple synthesis, and high stability. In this paper, two simple oligothiophenes, namely, DC5T and 2FDC5T with rhodanine-flanked structures were synthesized and used as donors in nonfullerene small-molecule organic solar cells (NSM-OSCs). Compared to DC5T, 2FDC5T with fluorine atoms substituted on the conjugated backbone exhibited a downshifted highest occupied molecular orbital (HOMO) energy level and blue-shifted light absorption. With IDIC-4F as a small-molecule acceptor, the 2FDC5T-based device exhibited much higher short-circuit current density and open-circuit voltage than the DC5T-based device. As a result, a promising power conversion efficiency (PCE) of 9.02% was achieved for the 2FDC5T/IDIC-4F device, which was 28% higher than that of the DC5T/IDIC-4F device (PCE = 7.03%). Further research indicated that fluorination on the oligothiophene donor assisted the optimization of the active layer morphology and the reduction in the trap-assisted recombination in the device, which could deeply explain the improvement in efficiency.

中文翻译：

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用于高性能非富勒烯小分子有机太阳能电池的氟化低聚噻吩供体

噻吩由于其优异的电荷传输性能，简单的合成和高稳定性而被广泛用于有机光伏中。本文合成了两个简单的寡聚噻吩，即具有若丹宁侧翼结构的DC5T和2FDC5T，并将其用作非富勒烯小分子有机太阳能电池（NSM-OSC）的供体。与DC5T相比，在共轭骨架上被氟原子取代的2FDC5T表现出下移的最高占据分子轨道（HOMO）能级和蓝移的光吸收。使用IDIC-4F作为小分子受体时，基于2FDC5T的设备显示出的短路电流密度和开路电压要远远高于IDF -4F。基于DC5T的设备。结果，2FDC5T / IDIC-4F器件的功率转换效率（PCE）达到了9.02％，比DC5T / IDIC-4F器件（PCE = 7.03％）高出28％。进一步的研究表明，在低聚噻吩供体上进行氟化有助于优化活性层的形态，并减少器件中陷阱辅助的重组，这可以深入地解释效率的提高。