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

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.