Ternary strategy enabling high-efficiency rigid and flexible organic solar cells with reduced non-radiative voltage loss

The ternary strategy has been identified as a feasible and effective way to obtain high-efficiency organic solar cells (OSCs). However, for most ternary OSCs, the voltage loss (V_loss) lies between those of the two binary devices, which inevitably limits the further efficiency improvements. Herein, a non-fullerene acceptor ZY-4Cl, possessing complementary absorption spectra and forming a cascade LUMO energy level alignment with the PM6:BTP-eC9 blend, was introduced as a third component to fabricate ternary OSCs. Compared to the binary blends, the ternary system exhibits reduced density of trap states, improved molecular ordering, and suppressed non-radiative recombination, and thereby yields an obviously lower V_loss than either of the binary OSCs. As a result, high efficiencies of 18.69% (certified as 18.2%) and 16.07% are obtained for the rigid and flexible OSCs, respectively. This work highlights the importance of suppressing non-radiative recombination in OSCs by using a ternary strategy and expands an effective avenue for the realization of efficient wearable electronics as novel photovoltaic power sources.