Enhancing Perovskite Solar Cell Performance by Interface Engineering Using CH₃NH₃PbBr_0.9I_2.1 Quantum Dots

TLDR

The study aims to rationally design interface engineering to enhance interfacial charge transfer in perovskite solar cells by incorporating MAPbBr3–xIx quantum dots between the perovskite film and the hole‑transporting material. The authors tune the Br:I ratio in MAPbBr3–xIx quantum dots to adjust their band edge positions, positioning the valence band relative to the perovskite and HTM to control hole transfer across the interface. When the quantum‑dot valence band lies between the perovskite valence band and the HTM HOMO, hole transfer is facilitated, yielding marked improvements in fill factor, short‑circuit current, and overall power‑conversion efficiency.

Abstract

To improve the interfacial charge transfer that is crucial to the performance of perovskite solar cells, the interface engineering in a device should be rationally designed. Here we have developed an interface engineering method to tune the photovoltaic performance of planar-heterojunction perovskite solar cells by incorporating MAPbBr3–xIx (MA = CH3NH3) quantum dots (QDs) between the MAPbI3 perovskite film and the hole-transporting material (HTM) layer. By adjustment of the Br:I ratio, the as-synthesized MAPbBr3–xIx QDs show tunable fluorescence and band edge positions. When the valence band (VB) edge of MAPbBr3–xIx QDs is located below that of the MAPbI3 perovskite, the hole transfer from the MAPbI3 perovskite film to the HTM layer is hindered, and hence, the power conversion efficiency decreases. In contrast, when the VB edge of MAPbBr3–xIx QDs is located between the VB edge of the MAPbI3 perovskite film and the highest occupied molecular orbital of the HTM layer, the hole transfer from the MAPbI3 perovskite film to the HTM layer is well-facilitated, resulting in significant improvements in the fill factor, short-circuit photocurrent, and power conversion efficiency.