Synthesis and Photovoltaic Properties of a Series of Narrow Bandgap Organic Semiconductor Acceptors with Their Absorption Edge Reaching 900 nm

Abstract

Three n-OS acceptors with Eg values of <1.4 eV were synthesized by introducing double-bond π-bridges into ITIC (ITVIC) and ITIC with monofluorine (ITVfIC) or bifluorine (ITVffIC) substituents on its end groups, and the structure–property relationships of the acceptors were systematically studied. The three n-OS films show broad absorption covering the wavelength range of 550–900 nm with narrow Eg values of 1.40 eV for ITVIC, 1.37 eV for ITVfIC, and 1.35 eV for ITVffIC. Additionally, the fluorine substitution downshifted the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels of the compounds. The photovoltaic properties of the n-OS acceptors were investigated by using a medium bandgap conjugated polymer J71 as a donor. The optimized polymer solar cells (PSCs) based on J71:ITVffIC demonstrated a power conversion efficiency (PCE) of 10.54% with a high Jsc of 20.60 mA cm–2 and a Voc of 0.81 V, and the highest Jsc reached 22.83 mA cm–2. The high Jsc values of...