Temperature-modulated crystal growth and performance for highly reproducible and efficient perovskite solar cells

The annealing temperature (T-a) effect on CH3NH3PbI3 perovskite solar cells (PSCs) was studied. By utilizing a two-step technique, the T-a dependences of the optical absorption, grain size, and crystallinity of a CH3NH3PbI3 thin film have been revealed. It is found that the grain size of the CH3NH3PbI3 film increases monotonically with T-a. Meanwhile, the decomposed PbI2 emerges when T-a exceeds 120 degrees C and its content increases rapidly as T-a increases further. Consequently, the optical absorption of the CH3NH3PbI3 film and the efficiency of PSCs reach their maximum at T-a = 120 degrees C simultaneously. The highest and average device performances of PSCs achieved via this method are 17.61% and 16.40%, respectively. These results confirm the key role played by temperature and provide a route to the performance-optimization of PSCs.