Improving the stability of MAPbI3 films by using a new synthesis route
Gerardo Gordillo, O.G. Torres, Maria Camila Abella, J.C. Peña, Ophyr Virgüez-Amaya
Abstract
This paper reports results of a study on the impact that the synthesis method and the replacement of the methylammonium (MA) cation by the formamidinium (FA) cation have on both morphology and degradation of MAPbI3 (MAPI) films when these are exposed to environmental conditions. This study was conducted with samples deposited using different routes based on growth methods both in solution and thermal evaporation, including one step spin coating and two-steps new growth routes where in a first step a layer of PbI2 is deposited by conventional evaporation and then a second layer of MAI (methylammonium iodide) is deposited by dipping and CSS (close spaced sublimation) methods respectively. The study revealed that the stability of MAPI films is significantly improved when are deposited using the two-steps synthesis routes. Evidence was found explaining that this behavior could be attributed to the fact that this type of MAPI films, grow with large grain sizes and low density of native and structural defects, characteristics that lead to a reduction of the ionic migration initiated in grain boundaries regions, where the degradation process generally begins.