Enhancing Perovskite Solar Cell Performance by Interface Engineering Using CH3NH3PbBr0.9I2.1 Quantum Dots

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 adjusting 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 MAPbI3 perovskite, the hole transfer from the MAPbI3 perovskite to the HTM layer is hindered and hence the power conversion efficiency decreases. On the contrary, when the VB edge of MAPbBr3-xIx QDs is located between the VB edge of MAPbI3 perovskite and the HOMO of HTM layer, the hole transfer from the perovskite to the HTM layer is well facilitated, resulting in significant improvements of fill factor, short-circuit photocurrent and power conversion efficiency.