Highly efficient quaternary organic photovoltaics by optimizing photogenerated exciton distribution and active layer morphology

Ternary strategy has been confirmed as an efficient method to improve the power conversion efficiency (PCE) of organic photovoltaics (OPVs). The 15.7% PCE is achieved from PM6:Y6 based binary OPVs. One nonfullerene acceptor Br-ITIC and fullerene derivative PC₇₁BM are selected as the third component on the basis of efficient binary OPVs, respectively. The optimized ternary OPVs exhibit 16.4% and 16.2% PCE with Br-ITIC and PC₇₁BM as the third component, respectively, corresponding to the short circuit current density (J_SC) of 25.5 mA cm⁻² vs. 25.6 mA cm⁻², open circuit voltage (V_OC) of 0.854 V vs. 0.836 V and fill factor (FF) of 75.1% vs. 75.6%. The advantage on photovoltaic parameters of two ternary OPVs may be recombined into one cell by employing PC₇₁BM as the fourth component. A 16.8% PCE is achieved from the optimized quaternary OPVs, resulting from the further increased J_SC of 25.8 mA cm⁻² and FF of 76.4% compared with the optimized ternary OPVs. The third party certificated PCE of quaternary OPVs is 16.2%. In comparison to 15.7% PCE of the binary OPVs, about 4.5% and 7.0% PCE improvement are step-by-step achieved from the optimized ternary and quaternary OPVs, respectively. Multi-components strategy may provide enough room to achieve highly efficient OPVs.