Much attention has been paid to the push-pullstructure organic small molecule(OSM) materials for photovoltaic(PV) application in the past decade, due to their facile reduction of energy band gap(Eg) and effective control of PV properties. π-bridge plays an important role in the push-pull-structure OSMs since an appropriate π-linkage is crucial for improving the PV performance of organic solar cells(OSCs). In this review, various π-bridge groups(thiophene, alkene, alkyne, arene and heterocycle) and the pertinent π-linkage effect will be systematically summarized.These results suggest that the in-depth study of the π-linkage effect is essential to deeply understanding the relationship between the molecular structure and property, thus improving PV performance.
本文设计合成了2种新型的基于9-芴酮(FN)的D-A-A'构型的有机小分子光伏给体材料TPAFNPI和TPAFNDI.2种结构均采用三苯胺(TPA)作为给电子单元,三键作为π桥,并引入不同的末端吸电子单元邻苯二甲酰亚胺(PI)和靛红(DI)进行端基修饰.这种D-A-A'结构不仅可以有效改善分子内电荷转移效应,同时也弥补了在9-芴酮上引入氰基的缺点,三苯胺(D)的扭转结构还可以避免由于过度聚集而形成较大的相分离分寸.通过调控末端吸电子单元有利于改善电子云分布,从而促进分子内的电荷传输,还有利于获得更低的最高占据轨道与最低空轨道能级.通过紫外-可见吸收光谱和循环伏安法对材料的光电性质进行探究,并将其作为给体材料与富勒烯受体(PC_(61)BM/PC_(71)BM)共混制备成本体异质结器件.结果显示,TPAFNPI和TPAFNDI均具有较窄的带隙,分别为1.75和1.72 e V.2种材料与PC_(71)BM混合后分别获得了1.05和1.01 V的开路电压,而靛红由于具有更强的吸电子性,从而使TPAFNDI具有更窄的带隙和更强的光吸收特性,其短路电流密度可达到11.46 m A·cm^(-2),光电转化效率为3.37%.
