Organic-Inorganic Hybrid Perovskite Solar Cells

Abstract

Quite high efficiencies exceeding 20% have been realized in solar cells incorporating organic-inorganic hybrid perovskites (APbX3), which have a unique structure with a center cation [A = CH3NH3+, HC(NH2) 2 + ] located within a PbX3− cage (X = I, Br, Cl). Superior characteristics of hybrid perovskite solar cells can be understood from the nature of optical transitions and the efficient carrier collection in the device. From these points of view, this chapter provides details on optical properties of various hybrid perovskite materials and carrier dynamics in the solar cells. In particular, based on the first-principles analyses of different perovskite materials, we present universal rules that allow the unified interpretation of the optical absorption phenomenon in APbX3 perovskites. The external quantum efficiency (EQE) analysis further reveals that high short-circuit current densities (>20 mA/cm2) observed in the perovskite solar cells originate from electric-field-assisted carrier collection and the suppressed optical losses in the devices. Although hybrid perovskites have quite favorable characteristics for solar cells, these materials exhibit rather intense phase change upon exposure to humid air. In this chapter, the degradation process of CH3NH3PbI3 in humid air, characterized by applying ellipsometry technique, is further presented and discussed.