Various Mechanisms of Additives in Different Additive Methods on the Crystallinity of Perovskite by Synchrotron Radiation Technology

Additives are one of the important means to improve the performance of perovskite solar cells. To explore the effects of different addition methods on the crystallinity of perovskite, in this paper, guanidine thiocyanate (GASCN) is added in three different methods, i.e., added in SnO₂ precursor solution; in PbI₂ precursor solution; or FAI precursor solution, respectively. The guanidine hydroiodide (GAI) and methylamine thiocyanate (MASCN) are selected as contrast additives to evaluate the role of GA⁺ and SCN⁻. Though the efficiency and stability of the perovskite solar cells with all additives are improved, the systematic study by grazing incidence wide-angle X-ray scattering (GIWAXS), quasi-in situ GIWAXS, and in situ X-ray diffraction (XRD) proved that the mechanism by the three different addition methods behaved in many different ways, which corresponded, respectively, to the surface of the SnO₂ electron transport layer, dominance orientation especially vertical growth of perovskite, or low-dimensional perovskite structure. This provides a new view for optimizing the appropriate synthesis conditions in the future.