High-performance organic solar cells based on a small molecule with thieno[3,2-b]thiophene as π-bridge

Abstract

Abstract Herein, we synthesized a new acceptor-π-donor-π-acceptor (A-π-D-π-A) type small molecule donor material BTTR based on thienyl-substituted benzo[1,2-b:4,5-b′]dithiophene (BDT-T) as the electron-donating core, thieno[3,2-b]thiophene (TT) along with two thiophene units as the π-bridge, and 3-ethylrhodanine (TR) as the electron-deficient end group. The optical, electrical, thermal properties and photovoltaic performance were investigated. BTTR shows strong absorption in the range of 300–700 nm, deep-lying HOMO energy level of −5.32 eV and high hole mobility of 1.01 × 10−3 cm2 V−1 s−1. The organic solar cells (OSCs) based on BTTR:PC71BM (1:0.8, w/w) blend with tetrahydrofuran (THF) solvent vapor annealing (SVA) exhibited an optimized power conversion efficiency (PCE) of 8.0% with an open circuit voltage (Voc) of 0.93 V, a short circuit current density (Jsc) of 13.2 mA cm−2, and a fill factor (FF) of 65.4% under the illumination of AM 1.5G, 100 mW cm−2. The good photovoltaic performance indicates BTTR could be a promising donor material in solution-processed OSCs.