A new non-fullerene acceptor based on the combination of a heptacyclic benzothiadiazole unit and a thiophene-fused end group achieving over 13% efficiency

Abstract

A new non-fullerene acceptor, namely Y10, based on dithienothiophen[3,2-b]-pyrrolobenzothiadiazole (TPBT) as the central core and 2-(6-oxo-5,6-dihydro-4H-cyclopenta[c]thiophen-4-ylidene)malononitrile (TC) as the electron-deficient end group, has been designed and synthesized. Y10 reveals a narrow optical energy gap (E^opt_g) of 1.35 eV with a broad absorption band from 600 to 900 nm. A wide bandgap polymer, J11, as the donor material (E^opt_g = 1.96 eV) is used to blend with Y10 for the construction of organic solar cell devices, which achieve an impressive power conversion efficiency (PCE) of 13.46% with an open circuit voltage (V_oc) of 0.89 V, a short circuit current (J_sc) of 21.21 mA cm⁻², and a fill factor (FF) of 71.55%, with thermal annealing treatment at 100 °C for 5 min and 0.8 wt% 1-chloronaphthalene (CN) as an additive. These results indicate that the incorporation of the TPBT unit as the central core and the TC unit as the electron-deficient end group provides an efficient strategy for the construction of high performance solar cells.