A facile method to improve the stability and efficiency of CsPbI2Br perovskite solar cells prepared at low temperature

CsPbI2Br has become the focus of researchers in recent years due to its excellent thermal stability compared to the organic-inorganic hybrid perovskites. However, it requires high temperature to form cubic phase, and it is difficult to maintain the cubic phase in the high humidity ambient. By adding 30 mu L levulinic acid (LA) to the CsPbI2Br precursor solution, cubic phase CsPbI2Br can be obtained by spin-coating three minutes (TMS) at room temperature (RT) instead of high temperature. Based on the TMS, highly quality cubic phase CsPbI2Br film can be obtained at 80 degrees C annealing temperature, the stability of cubic phase CsPbI2Br can be significantly improved by adding LA in the CsPbI2Br precursor solution. Based on this, CsPbI2Br cells without LA achieve 11.68% power conversion efficiency (PCE) at low temperature of 80 degrees C and the corresponding stabilized power output is 10.31%. Furthermore, 10 mu L LA addition CsPbI2Br cells keep its 50% PCE after 10 days under 35%RH and RT. This has found a new way to improve the stability of inorganic perovskite solar cells, and increasing its potential in flexible solar cells.