Temperature Dependent Charge Carrier Dynamics in Formamidinium Lead Iodide Perovskite

The fundamental opto-electronic properties of organic-inorganic hybrid perovskites are strongly affected by their structural parameters. These parameters are particularly critical in formamidinium lead iodide (FAPbI₃), in which its large structural disorder leads to a non-perovskite yellow phase that hinders its photovoltaic performance. A clear understanding of how the structural parameters affect the opto-electronic properties is currently lacking. We have studied the opto-electronic properties of FAPbI₃ using microwave conductivity measurements. We find that the mobility of FAPbI₃ increases at low temperature following a phonon scattering behavior. Unlike methylammonium lead iodide (MAPbI₃), there are no abrupt changes after the low-temperature β/γ phase transition and the lifetime is remarkably long. This absence of abrupt changes can be understood in terms of the reduced rotational freedom and smaller dipole moment of the formamidinium, as compared to methylammonium.