Finely modulated asymmetric nonfullerene acceptors enabling simultaneously improved voltage and current for efficient organic solar cells

Abstract

It is a great challenge to simultaneously improve the short-circuit current density (J_sc) and open-circuit voltage (V_oc) of organic solar cells (OSCs) owing to the trade-off effect between the two photovoltaic parameters. Delicate chemical structure modulation of the active layer materials is always one of the effective strategies to address this issue. In this work, following a simple and efficient strategy through fine-tuning the molecular configuration in combination with the side chain modulation to address the issue, three non-fullerene acceptors (NFAs), 5T-2C8-IN, 5T-2C8-Cl and 5T-2C8-2Cl with a five-thiophene (5T) fused asymmetric molecular backbone and octyl side chains at the terminal position of the molecular backbone, have been designed and synthesized. Among them, the 5T-2C8-2Cl based photovoltaic device showed a power conversion efficiency (PCE) of 13.02% with a simultaneously improved V_oc of 0.802 V and a J_sc of 24.97 mA cm⁻² compared with the device of the control acceptor 6T-2C8-2Cl with a PCE of 12.43%, a V_oc of 0.785 V and a J_sc of 24.40 mA cm⁻².