Additive effect of lanthanide compounds into perovskite layer on photovoltaic properties and electronic structures

Abstract

Fabrication and characterization of lanthanide compound doped CH3NH3PbI3 (MAPbI3) perovskite solar cells have been performed for improving the photovoltaic properties with long-term stabilities of conversion efficiency. The purpose of this research is to investigate additive effect of formamidinium iodine (FAI) and lanthanide compound into the perovskite layer for improving carrier diffusion and mobility in the perovskite layer. Incorporation of FAI and europium chloride (EuCl2) into the perovskite crystals maintained the stability of conversion efficiency for 30 days. The photovoltaic properties were based on the crystal growth and orientation with suppression of decomposition, thermodynamic stabilities, and the narrow band dispersion with decrease of effective mass. In contrast case, addition of samarium or terbium compound reduced the stabilities, and suppressed the carrier mobility owing to the flat band dispersion of localized d orbital of samarium atom or 4 f orbital of terbium atom near valence band state. The annealing treatment improved the crystal orientation related to the carrier diffusion with inhibiting recombination, improving short circuit current density and external quantum efficiency. The perovskite crystal doped with EuCl2 and FAI have high advantage to apply for practical use of the photovoltaic devices with long-term stability.