Ligand engineering on CdTe quantum dots in perovskite solar cells for suppressed hysteresis

Solar cells employing lead halide perovskites as light absorbers have been one hot topic in recent years due to their amazing device performance and commercialization potential. Yet, there exist challenges on the way to their practical use, including long-term stability, and J-V hysteresis. Herein, we demonstrate an improved contact between perovskite and hole transporting layer (HTL) by using CdTe quantum dots, wherein the capping ligands on quantum dots are systematically investigated. The devices with the CdTe quantum-dot-in-perovskite solids interlayer achieve a high efficiency (~ 19.3%, averaged), and more importantly, a significantly reduced hysteresis, which is superior to devices with CdTe QDs capped by other ligands (PbI₂, CH₃NH₃I, oleic acid). We attribute this superior device performance to the congeneric junction contact between perovskite and CdTe quantum-dot-in-perovskite layer. Furthermore, we reveal that the reduced hysteresis is partially contributed from faster hole extraction at the interface thanks to the high hole mobility in CdTe. These findings shed lights on the future design of quantum dots for perovskite optoelectronics in the perspective of ligand engineering.