Highly efficient ternary solar cells with reduced non-radiative energy loss and enhanced stability via two compatible non-fullerene acceptors

A ternary strategy by introducing a third component into a binary host system has been proven to be a simple and promising method to boost the power conversion efficiency (PCE) and stability of organic solar cells (OSCs). Herein, a high efficient ternary OSC is fabricated, wherein, a non-fullerene acceptor, namely MOIT-M, is introduced as a third component into the PM6:BTP-eC9 blend. MOIT-M possesses good complementary absorption spectra and aligned cascade energy levels with the host binary blend, which benefits light harvesting, exciton dissociation, and charge transport. Moreover, MOIT-M exhibits good miscibility with BTP-eC9, forming a well-mixed phase, which improves molecular packing for better charge transport and optimizes ternary blend morphology. Notably, the incorporation of MOIT-M suppresses non-radiative recombination, leading to reduced non-radiative energy losses (ΔE_nr). As a result, the ternary OSC exhibits a significantly increased PCE of 18.5% with a lower ΔE_nr of 0.21 eV in comparison with the control binary PM6:BTP-eC9 device with a PCE of 17.4% and a ΔE_nr of 0.24 eV. In addition, the ternary OSC displays better storage stability compared to the PM6:BTP-eC9 system. This work indicates that a ternary strategy via combining two compatible small molecule acceptors is effective to simultaneously improve the efficiency and stability of OSCs.