Subbiah Jegadesan, Lee Calvin J, Mitchell Valerie D, Jones David J
School of Chemistry, Bio21 Institute, University of Melbourne, Parkville, Melbourne, Victoria 3010, Australia.
ACS Appl Mater Interfaces. 2021 Jan 13;13(1):1086-1093. doi: 10.1021/acsami.0c20389. Epub 2020 Dec 21.
Controlling the nanoscale morphology of the photoactive layer by fine-tuning the molecular structure of semiconducting organic materials is one of the most effective ways to improve the power conversion efficiency of organic solar cells. In this contribution, we investigate the photovoltaic performance of benzodithiophene (BDT)-based p-type small molecules with three different side chains, namely alkyl-thio (BTR-TE), dialkylthienyl (BTR), and trialkylsilyl (BTR-TIPS) moieties substituted on the BDT core, when used alongside a nonfullerene acceptor. The side-chain changes on the BDT core are shown to have a profound effect on energy levels, charge generation, recombination, morphology, and photovoltaic performance of solid-state molecules. Compared with BTR and BTR-TIPS, BTR-TE-based single-junction binary blend solar cells show the best power conversion efficiency (PCE) of 13.2% due to improved morphology and charge transport with suppressed recombination. In addition, we also achieved relatively good performances for ternary blend solar cells with a PCE of 16.1% using BTR-TE as a third component. Our results show that side-chain modification has a significant effect on modulating active layer morphology, and in particular that thioether side-chain modification is an effective way to achieve optimum morphology and performance for organic photovoltaic (OPV) devices.
通过微调半导体有机材料的分子结构来控制光活性层的纳米级形态，是提高有机太阳能电池功率转换效率的最有效方法之一。在本论文中，我们研究了基于苯并二噻吩（BDT）的p型小分子与三种不同侧链（即烷基硫基（BTR-TE）、二烷基噻吩基（BTR）和三烷基硅基（BTR-TIPS））在BDT核上取代的分子，与非富勒烯受体一起使用时的光伏性能。结果表明，BDT核上的侧链变化对固态分子的能级、电荷产生、复合、形态和光伏性能有深远影响。与BTR和BTR-TIPS相比，基于BTR-TE的单结二元混合太阳能电池由于形态改善和电荷传输以及复合抑制，显示出13.2%的最佳功率转换效率（PCE）。此外，我们还使用BTR-TE作为第三组分，实现了三元混合太阳能电池相对较好的性能，PCE为16.1%。我们的结果表明，侧链修饰对调节活性层形态有显著影响，特别是硫醚侧链修饰是实现有机光伏（OPV）器件最佳形态和性能的有效方法。
