Bi3+-doped CH3NH3PbI3: Red-shifting absorption edge and longer charge carrier lifetime

Ion doping is an effective approach to improve the properties of hybrid perovskite CH3NH3PbI3, such as chemical stability and solar absorption. Here Bi3+-doped CH3NH3PbI3 was synthesized via cooling crystallization process in aqueous solution. Along with the Bi3+ doping, the bandgap of CH3NH3PbI3 could be significantly narrowed, by the maximum value of 140 meV at the optimal doping level of 1.6 M %. Transient photovoltage measurement (TPV) revealed the Bi3+-doped CH3NH3PbI3 could achieve a charge carrier lifetime of 280 μs, which was almost twice longer than that of pristine CH3NH3PbI3 (157 μs). The prolonged carrier lifetime of Bi3+-doped CH3NH3PbI3 was supposed to be attributed to its lower packing factor (PF), which was caused by the CH3NH3+ vacancy (VMA) after doping This work provides a new approach to tune the band gap and charge carrier lifetime of the hybrid perovskite CH3NH3PbI3, which should be promising to further improve the performance of perovskite-based photovoltaic devices.