Nakano Kyohei, Terado Kosuke, Kaji Yumiko, Yoshida Hiroyuki, Tajima Keisuke
RIKEN Center for Emergent Matter Science (CEMS), 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.
Graduate School of Science and Engineering, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan.
ACS Appl Mater Interfaces. 2021 Dec 22;13(50):60299-60305. doi: 10.1021/acsami.1c19275. Epub 2021 Dec 10.
Y6 is a recently developed non-fullerene electron acceptor (NFA) with dithienothiophen[3.2-]-pyrrolobenzothiadiazole as the central unit and improves the performance of organic photovoltaics (OPVs) in combination with many electron-donor polymers. Although Y6 has desirable electronic properties for OPVs, the origin of its superiority as an acceptor is unclear. This study empirically investigates why Y6 is an excellent acceptor by comparing Y6 with F8IC, an analogue with a similar electronic structure, in bulk heterojunction (BHJ) OPVs with various electron-acceptor concentrations. The difference in the performance between Y6 and F8IC appears only at high concentrations, suggesting that it originates from the aggregation structures of the NFAs in the BHJs. Electric current loss analysis reveals that the exciton loss and non-geminate recombination are suppressed more strongly in Y6 OPVs than in F8IC OPVs. Variable angle spectroscopic ellipsometry shows that Y6 molecules align in the in-plane direction at high concentrations, contributing to the high charge generation rate via efficient exciton collection.
Y6是一种最近开发的非富勒烯电子受体（NFA），以二噻吩并噻吩[3.2-] - 吡咯并苯并噻二唑为中心单元，与许多电子供体聚合物结合可提高有机光伏（OPV）的性能。尽管Y6对OPV具有理想的电子特性，但其作为受体的优越性来源尚不清楚。本研究通过在具有不同电子受体浓度的体异质结（BHJ）OPV中，将Y6与具有相似电子结构的类似物F8IC进行比较，实证研究了Y6为何是一种优异的受体。Y6和F8IC之间的性能差异仅在高浓度时出现，这表明它源于BHJ中NFA的聚集结构。电流损失分析表明，与F8IC OPV相比，Y6 OPV中的激子损失和非成对复合受到更强的抑制。可变角度光谱椭偏仪表明，Y6分子在高浓度下沿面内方向排列，通过有效的激子收集有助于提高电荷产生率。
