Impact of MAPbBr3 Additives on Crystallinity and Charge Carrier Dynamics of Mixed Perovskite Films

Organic-metal halide perovskite is one of the most promising candidates for the next generation solar cell material owing to its superior photo-electric properties and relatively simple fabrication process. In particular, FAPbI 3 turned out to be very suitable for efficient solar cell due to its low band gap energy $(\sim 1.5\ \text{eV})$ . However, FAPbI 3 shows the crystal phase instability between unfavourable yellow trigonal δ-phase and perovskite-type black cubic a-phase at room temperature. To stabilize it, various additives such as MACl, Cs and MAPbBr 3 have been proposed and studied. Recently, there was a report that 0.8 mol% of MAPbBr 3 additive stabilizes the crystal phase of FAPbI 3 , and subsequently, a photo conversion efficieny (PCE) of 25.2% was achieved [1]. However, the influence of MAPbBr 3 additives on charge carrier dynamics and its correlation with crystallinity is still unrevealed.