Three dicyanostyrylbenzene (DCS)-based small-molecule nonfullerene acceptors (SM-NFAs), NIDCS-MO, NIDCS-PrO, and NIDCS-PeO, bearing alkoxy chains with different lengths from methoxy to pentyloxy are synthesized to investigate the alkyl chain length effect on the performance of all-small-molecule organic solar cells (SM-OSCs). The optical properties and frontier molecular orbital (FMO) energy levels of the three SM-NFAs are virtually identical in both solution and neat films. In contrast, their photovoltaic performance in SM-OSCs with a common small-molecule donor 7,7′-(4,4-bis(2-ethylhexyl)-4H-silolo[3,2-b:4,5-b′]dithiophene-2,6-diyl)bis(6-fluoro-4-(5′-hexyl-[2,2′-bithiophen]5-yl)benzo[c][1,2,5]thiadiazole) (DTS-F) is significantly varied. In particular, the open-circuit voltage (V_OC) is gradually increased from 0.85 to 1.00 V with the increase in the alkyl chain length. By cyclic voltammetry (CV) and impedance spectroscopy, it is revealed that the energetic landscape of the blend films is negligibly changed depending on the alkyl chain length. However, it is found that voltage loss from the nonradiative recombination in SM-OSCs with longer alkyl chain acceptors is considerably reduced due to denser blend film formation, which is evidenced by CV studies with various conditions and the morphology analysis of the blend films using X-ray diffraction (XRD), atomic force microscopy (AFM), and scanning transmission electron microscopy (STEM).

中文翻译：

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高度结晶性富勒烯受体的烷基链长对全分子有机太阳能电池开路电压的影响

合成了三种基于双氰基苯乙烯基苯（DCS）的小分子非富勒烯受体（SM-NFA），NIDCS-MO，NIDCS-PrO和NIDCS-PeO，它们具有从甲氧基到戊氧基长度不同的烷氧基链，以研究烷基链长度效应全小分子有机太阳能电池（SM-OSC）的性能 在溶液和纯净薄膜中，三种SM-NFA的光学性质和前沿分子轨道（FMO）能级实际上是相同的。相反，它们在具有常见小分子供体7,7'-（4,4-双（2-乙基己基）-4 H -silolo [3,2- b：4,5- b ′]二噻吩-2,6-二基）双（6-氟-4-（5'-己基-[2,2'-联噻吩] 5-基）苯并[ c] [1,2,5]噻二唑（DTS-F）显着不同。特别地，开路电压（V _OC）逐渐从0.85提高到1.00 V的在烷基链长度的增加。通过循环伏安法（CV）和阻抗光谱法，发现共混膜的高能态随烷基链长的变化可忽略不计。然而，发现由于具有更稠密的共混膜形成，具有更长烷基链受体的SM-OSC中非辐射重组产生的电压损失大大降低，这在各种条件下的CV研究以及使用X对共混膜的形态分析中得到了证明。射线衍射（XRD），原子力显微镜（AFM）和扫描透射电子显微镜（STEM）。