Organic solar cells based on non-fullerene acceptors containing thiophene [3,2-b] pyrrole

In this work, thiophene[3,2-b] pyrrole (TP) was introduced to construct two novel fused-ring conjugated non-fullerene acceptors (NFAs), named as PTBTP-2F and PTBTP-4F. By fusing two pyrrole rings on both sides of an indacenodithiophene (IDT) unit, a brand-new central core based on TP block (denoted as PTBTP) was achieved to serve as the D core to construct an A-D-A type NFA together with two accepting units (IC–F and IC-2F). Benefitting from the nitrogen atom in the pyrrole ring, both PTBTP-2F and PTBTP-4F exhibited great film forming property as well as high LUMO energy levels of −4.09 eV and −4.11 eV for PTBTP-2F and PTBTP-4F, respectively. Since IC-2F presents stronger electron-withdrawing capability than IC-F, PTBTP-4F demonstrated red-shifted absorptions in solution/film in comparison with PTBTP-2F. When blending with donor PBDB-T, the PTBTP-2F fabricated devices achieved an average power conversion efficiency (PCE) of 11.14% with a V_OC of 0.91 V, a J_SC of 17.89 mA cm⁻² and an FF of 68.66%, while the PTBTP-4F fabricated devices afforded a PCE of 12.33% with a V_OC of 0.86 V, a J_SC of 20.74 mA cm⁻² and an FF of 69.02%.