Efficient organic ternary solar cells with the third component as energy acceptor

Abstract

A smart ternary strategy was designed to simultaneously improve utilization of excitons on PCDTBT and enhance photon harvesting in long wavelength range by doping appropriate SQ into the dominating PCDTBT:PC71BM system. The phase separation can be finely optimized by adjusting SQ doping ratio, resulting in efficient charge carrier transport channels and the enhanced photon harvesting in the ternary active layers. The dopant SQ provides a potential route for further utilizing the excitons on PCDTBT, especially for the excitons unattainable to the PCDTBT/PC71BM interfaces. The excitons on PCDTBT can transfer their energy to SQ through Förster energy transfer, and then be dissociated into free charge carriers at SQ/PC71BM interface. The holes generated on SQ can be effectively transferred to PCDTBT and then transported along the channels formed by PCDTBT to anode. Consequently, the champion PCE of ternary solar cells arrives to 7.62% with 9wt% SQ doping ratio in donors, which is much higher than the PCE of 6.54% for PCDTBT:PC71BM-based or 1.95% for SQ:PC71BM-based solar cells.