Efficient Charge Transfer and Carrier Extraction in All-Polymer Solar Cells Using an Acceptor Filler

All-polymer solar cells (all-PSCs) exhibit considerably improved mechanical and thermal stability than their polymer-fullerene counterparts. Despite their advantages, the power conversion efficiencies of all-PSCs are still lower than those of polymer-fullerene PSCs. In this study, we demonstrate that introducing a small amount of fullerene or non-fullerene acceptors as filler into the photoactive layer of PBDBT:N2200 all-PSCs can enhance charge transport properties and, thereby, the device performance. An appreciable enhancement (similar to 21%) in the power-conversion efficiencies (PCEs) of all-PSCs, from 6.13% to 7.42%, is obtained when fullerene with the amount of 25 wt % PBDBT is added. The performance improvement is primarily from the enhanced short circuit current density (J(SC)), which can be attributed to the enhanced exciton dissociation, reduced charge recombination, and balanced charge transport in the prescence of the fullerene filler. Similar behavior is also observed when fullerene is replaced by ITIC molecules. Importantly, the fullerene filler shows a negiligible effect on the device storage and light-soaking stability. Therefore, all-PSCs incorporating a proper selected acceptor filler is an efficient way to improve device performance without sacrificing stability. We believe that our study can pave a useful approach for developing stable and high performance PSCs.