Another research team comprises Prof. Yan Keyou (1st left), Prof. Xu Jianbin (2nd left) and doctoral tudents discovered nonstoichiometric acid–base reaction (NABR) as reliable synthetic route to highly stable CH3NH3PbI3 perovskite film for the production solar cells. The NABR perovskite film is stable for two months with negligible PbI2-impurity under 65% humidity, whereas other perovskites prepared by
traditional methods degrade distinctly after two weeks.The result was published in the November issue of Nature Communications.