Study on the side chain effect of A2-A1-D-A1-A2 type non-fullerene acceptors matched with P3HT

Because of the advantages of low cost, stability and easy synthesis, poly(3-hexylthiophene) (P3HT) was the most classic photovoltaic polymer and promoted the rapid progress of fullerene-based organic solar cells (OSCs) during 2005–2015. In comparison with A-D-A type non-fullerene acceptors (NFAs), A2-A1-D-A1-A2 type molecules can realize higher open-circuit voltage (VOC) and also match well with P3HT. Hence, here we modified the classic A2-A1-D-A1-A2 type NFA of BTA3 by altering the side chains at three different positions, and synthesized five new materials of BTA3b-3f to investigate the structure-properties relationship. By fine-tuning the side chains at middle D unit, BTA3b, BTA3c and BTA3d show totally different power conversion efficiencies (PCEs) of 5.95, 3.80 and 4.74% respectively, which demonstrate the modification of D unit can significantly influence the intermolecular interaction. On the other hand, with the modulation of side chains at A1 and A2 units, BTA3e and BTA3f show relatively high PCEs of 5.48 and 6.15% respectively. Our results indicate the systematical side chain engineering for A2-A1-D-A1-A2 type NFAs play a vital role to improve the photovoltaic performance of P3HT-based OSCs.