A Realistic Model of Temperature Dependent Carrier Diffusion Constant in Mapbi3 Films

The charge carrier mobility in perovskites is known to be affected by temperature. However, at low temperatures the perovskite film bears interfacial strains by deformation between the film and its substrate with difference coefficients of thermal expansion. Herein we provide a more realistic temperature-dependent carrier dynamics model involving both interfacial strain effect and intrinsic optoelectmnic properties. The interfacial strain of a MAPbI(3) film is confirmed through in-situ temperature-dependent X-ray diffractions. The carrier dynamics at different temperatures are unraveled using carrier dynamics fittings to time-resolved photoluminescence decays. An abnormal drop in carrier mobility is revealed with continuously decreasing temperature. The strain affects the trap density in films thus declines the carrier mobility at low temperatures. The carrier losses at the buried surface become significant at low temperatures due to the interfacial strain. This work provides a reminder that substrates should be carefully considered in temperature-related applications of perovskites.