Highly Efficient and Stable MAPbI3 Perovskite Solar Cell Induced by Regulated Nucleation and Ostwald Recrystallization

Perovskite solar cells have attracted great attention in recent years, due to their high conversion efficiency and solution-processable fabrication. However, most of the solar cells with high efficiency in the literature are prepared employing TiO2 as electron transport material, which needs sintering at a temperature higher than 450 degrees C, and is not applicable to flexible device and low-cost fabrication. Herein, the MAPbI(3) perovskite solar cells are fabricated at a low temperature of 150 degrees C with SnO2 as the electron transport layer. By dropping the antisolvent of ethyl acetate onto the perovskite precursor films during the spin coating process, compact MAPbI(3) films without pinholes are obtained. The addition of ethyl acetate is found to play an important role in regulating the nucleation, which subsequently improves the compactness of the film. The quality of MAPbI(3) films are further improved significantly through Ostwald recrystallization by optimizing the thermal treatment. The crystallinity is enhanced, the grain size is enlarged, and the defect density is reduced. Accordingly, the prepared MAPbI(3) perovskite solar cell exhibits a record-high conversion efficiency, outstanding reproducibility, and stability, owing to the reduced electron recombination. The average and best efficiency reaches 19.2% and 20.3%, respectively. The device without encapsulation maintains 94% of the original efficiency after storage in ambient air for 600 h.