Efficient Organic Solar Cells with a High Open-Circuit Voltage of 1.34 V

The of main observation and conclusion One of the most important challenges that hinders the power conversion efficiencies (PCEs) of organic solar cells (OSCs) is the modest open-circuit voltages (V-OC) due to large energy losses. The large driving force during for charge generation and the non-radiative recombination are the main causes of energy losses. To maximize the V-OC of OSCs, herein, we modulate the end-groups and design a non-fullerene acceptor ITCCM-O, which shows a bandgap of 2.0 eV. By blending a polymer donor named J52, the device demonstrates a PCE of 5.5% with an outstanding V-OC of 1.34 V, which is the highest value for single-junction OSCs over 5% PCEs. The high V-OC is benefited from 1) the negligible driving force for charge transfer, and 2) the suppressed non-radiative recombination loss, as low as 0.22 V.