Ternary organic solar cells with double side chain fullerene derivative as guest electron acceptors in PM7:Y6 blend films

In this paper, a fullerene derivative dihydronaphthyl-based C70 bisadduct (NC70BA) was used as a guest acceptor and introduced into PM7:Y6 binary films to fabricate ternary organic solar cells (OSCs). A high power conversion efficiency (PCE) of up to 15.70% was achieved after the addition of NC70BA to PM7:Y6 binary films with an open-circuit voltage (VOC) of 0.870 V, a short-circuit current density (JSC) of 25.35 mA cm−2, and a fill factor (FF) of 71.2%. NC70BA upshifts the lowest unoccupied molecular orbital (LUMO) energy levels of the blend acceptor and enlarges the energy bandgap. In addition, the optimized ternary films enhance the short wavelength photon harvesting intensity, improve the exciton dissociation and charge extraction, and improve the surface morphology and crystallinity of the ternary photoactive layer. As a result, the VOC, JSC and FF of the ternary OSCs simultaneously improve compared with those of PM7:Y6 binary OSCs. This study presents an effective method to improve the PCE by adopting a ternary strategy and NC70BA as a guest acceptor.