The preparation of four different star-shaped donor (D)âÏâacceptor (A) small molecules (N(Ph-1T-DCN-Me)3, N(Ph-2T-DCN-Me)3, N(Ph-2T-DCN-Hex)3 and N(Ph-3T-DCN-Hex)3) possessing various oligothiophene Ï-bridge lengths and their use in solution-processed bulk heterojunction small molecule solar cells is reported. Optical and electrochemical data show that increasing oligothiophene Ï-bridge length leads to a decrease of the optical band gap due to a parallel increase of the highest occupied molecular orbital (HOMO) level. Furthermore, subtle modifications of a molecular Ï-bridge length strongly affect the thermal behavior, solubility, crystallization, film morphology and charge carrier mobility, which in turn significantly change the device performance. Although the moderately increasing oligothiophene Ï-bridge length uplifts the HOMO level, it nevertheless induces an increase of the efficiency of the resulting solar cells due to a simultaneous improvement of the short circuit current (Jsc) and fill factor (FF). The study demonstrates that such an approach can represent an interesting tool for the effective modulation of the photovoltaic properties of the organic solar cells (OSCs) at a moderate cost.
本文报道了四种不同星形供体(D)——受体(A)小分子(N(Ph-1T-DCN-Me)3、N(Ph-2T-DCN-Me)3、N(Ph-2T-DCN-Hex)3和N(Ph-3T-DCN-Hex)3)的制备,这些小分子具有不同的
噻吩-桥长度,并用于溶液加工的体异质结小分子太阳能电池。光学和电
化学数据表明,
噻吩-桥长度的增加会导致光带隙的减小,这是由于最高被占分子轨道(HOMO)
水平的平行增加。此外,分子-桥长度的细微变化会强烈影响热性能、溶解度、结晶、薄膜形态和电荷载流子迁移率,进而显著改变器件性能。虽然适度增加
噻吩-桥长度会提升HOMO
水平,但由于短路电流(Jsc)和填充因子(FF)同时提高,它仍然可以提高太阳能电池的效率。该研究表明,这种方法可以成为有效调节有机太阳能电池(OSC)的光电性能的有趣工具,且成本适中。