Perovskite FA1-xMAxPbI3 for Solar Cells: Films Formation and Properties

Organic-inorganic hybrid perovskite formamidinium lead triiodide NH2CHNH2PbI3 (FAPbI3), methylammonium lead triiodide CH3NH3PbI3 (MAPbI3) and formamidinium methylammonium lead triiodide (NH2CHNH2)1-x(CH3NH2)xPbI3 (FA1-xMAxPbI3) thin films were synthesized and deposited on indium tin oxide glass substrates by spin coating process. Thin films of mixed FA1-xMAxPbI3 (x = 0-1) perovskites obtained by mixing FAPbI3 and MAPbI3 in different proportions. The morphological, structural and optical proprieties of all synthetized perovskites have been analyzed as a function of the MA/FA ratio. X-ray diffraction analyses indicated the formation a cubic perovskite phase with space group Pm-3m in the composition range 0 ≤ x ≤ 1. Mixed perovskites FAMAPbI3 showed a high absorbance in the infrared region 780-900 nm. The band gap energy estimated from absorbance spectral measurements for FAMAPbI3 thin films ranges from 1.50 eV for FAPbI3 to 1.56 eV for MAPbI3, respectively. The overall PL emissions of mixed FA/MA perovskite thin films are located in intermediate values between 773 nm and 810 nm.