Cathode modification in planar hetero-junction perovskite solar cells through a small-molecule zwitterionic carboxylate

A new carboxylate functionalized small molecule non-conjugated zwitterion, HDAC was proposed for its feasible one-step synthetic procedure. It can be used as an efficient interlayer to improve the fullerene/cathode interface of inverted planar heterojunction perovskite solar cells. A HDAC modified device could increase the power conversion efficiency from 15% to 17%. The main increase of the performance parameter lies on the increase of fill factor from around 72% to 80%, which could be attributed to the formation of interface dipole and elimination of potential barrier at the interface of electron transporting layer and cathode. This work brings up a simple design principle for efficient interfacial materials in perovskite solar cells.