Efficient small molecular ternary solar cells by synergistically optimized photon harvesting and phase separation

Abstract

Recently, power conversion efficiency (PCE) of organic solar cells has been increased up to about 10% by using solvent additives or mixed solutions to elaborately adjust phase separation which is a great challenge for large scale production. We report a champion PCE of 7.40% for solution-processed small molecule ternary SMPV1 : DIB-SQ : PC₇₁BM solar cells by only adjusting the DIB-SQ doping ratio in donors without any treatments on the blend solutions or active layers. The champion PCE of ternary solar cells is larger than the champion PCEs sum (6.98%) of binary solar cells with SMPV1 : PC₇₁BM or DIB-SQ : PC₇₁BM as the active layers. The PCE improvement should be attributed to the synergistic enhancement of photon harvesting, exciton dissociation, charge carrier transport and collection by the appropriate DIB-SQ doping ratio in donors. The experimental results on morphology, crystallinity, phase separation and charge carrier mobility of active layers well support the PCE improvement in ternary solar cells with a 10 wt% DIB-SQ doping ratio in donors.