S⋯N Conformational Lock Acceptor Based on Indacenodithiophene (IDT) Structure and High Electronegative Terminal End Group.

High-performance organic semiconductors should have good spectral absorption, a narrow energy gap, excellent thermal stability and good blend film morphology to obtain high-performance organic photovoltaics (OPVs). Therefore, we synthesized two IDTz-based electron acceptors in this research. When they were blended with donor PTB7-Th to prepare OPV devices, the PTB7-Th:IDTz-BARO-based binary OPVs exhibited a power conversion efficiency (PCE) of 0.37%, with a short-circuit current density ( J sc ) of 1.24 mA cm -2 , a fill factor (FF) of 33.99% and an open-circuit voltage ( V oc ) of 0.87 V. The PTB7-Th:IDTz-BARS-based binary OPVs exhibited PCE of 4.39%, with J sc of 8.09 mA cm -2 , FF of 54.13% and V oc of 1.00 V. The results show the strong electronegativity terminal group to be beneficial to the construction of high-performance OPV devices. Highlights: (1) Two new acceptors based on 5,5'-(4,4,9,9-tetrakis (4-hexylphenyl)-4,9-dihydro-s-indaceno [1,2-b:5,6-b'] dithiophene-2,7-diyl) dithiazole (IDTz) and different end groups (BARS, BARO) were synthesized; (2) BARS and BARO are electron-rich end groups, and the electron acceptors involved in the construction show excellent photoelectric properties. They can properly match the donor PTB7-Th, and show the appropriate surface morphology of the active layer in this work; (3) Compared with IDTz-BARO, IDTz-BARS has deeper LUMO and HOMO energy levels. In combination with PTB7-Th, it shows 4.39% device efficiency, 8.09 mA cm -2 short-circuit current density and 1.00 V open circuit voltage.