Raman Temperature Coefficients and Thermal Conductivity of Methylammonium Lead Bromide Perovskite Materials

Interest in the organic-inorganic hybrid perovskite materials has exploded in recent years due to the dramatic increase in the perovskite solar cells' solar power conversion efficiency and the potential for low manufacturing costs of such devices. Unfortunately, these materials and the solar cells based upon them suffer from instability due to environmental factors such as humidity, ultraviolet light, and heat. This motivates the investigation of the thermal conductivity and thermal diffusivity of these materials. The first experimental and theoretical studies found that the thermal conductivity of perovskites is rather low, i.e., below 1 W/mK at room temperature. We used the Raman optothermal technique, previously developed for graphene [1], in order to study in-plane and cross-plane thermal properties of perovskites and their dependence on temperature and defects. The temperature-dependent Raman spectra were obtained under 633-nm laser excitation. The thermal conductivity data obtained by the optothermal Raman technique will be compared with that of other methods. [1] A. A. Balandin, “Thermal properties of graphene and nanostructured carbon materials,” Nature Mater., 10, 569 (2011).