Temperature Dependence of the Urbach Energy in Lead Iodide Perovskites


To gain insight into the properties of photovoltaic and light-emitting materials, detailed information about their optical absorption spectra is essential. Here we elucidate the temperature dependence of such spectra for methylammonium lead iodide (CH3NH3PbI3), with specific attention to its sub-band gap absorption edge (often termed Urbach energy). On the basis of these data, we first find clear further evidence for the universality of the correlation between the Urbach energy and open-circuit voltage losses of solar cells. Second, we find that for CH3NH3PbI3 the static, temperature-independent contribution of the Urbach energy is 3.8 ± 0.7 meV, which is smaller than that of crystalline silicon (Si), gallium arsenide (GaAs), indium phosphide (InP), or gallium nitride (GaN), underlining the remarkable optoelectronic properties of perovskites.

Defect density comparison for several semiconductors
Static Urbach energy values comparison, obtained from the temperature measurement, for opto-electronically most relevant semiconductor mono-crystals and for halide perovskite thin film. Perovskites have extremely low density of electronically active defects.

Contact:Martin Ledinský
Collaborating institutions: King Abdullah University of Science and Technology (KAUST), Saudi Arabia