Thermal conductivity and diffusivity of triple-cation perovskite halide materials for solar cells

Abstract

We report on the measurement of thermal conductivity and thermal diffusivity by a modulated thermoreflectance microscopy technique on a mixed-cation perovskite material [Cs0.05(formamidinium0.83methylammonium0.17)0.95Pb(I0.83Br0.17)3] widely applied for solution-processed perovskite solar cells. Such materials are supposed to present improved thermal stability compared to methylammonium-based single cation perovskites. Our measurements are performed on perovskite/TiO2/SnO2:F/SiO2 structures, with perovskite thicknesses ranging between 250 nm and 1000 nm. This configuration is the one of a real solar cell, with the same substrate and intermediate layers as of an operating device. We measured a thermal conductivity kper of 0.26 ± 0.03 W m-1 K-1 and a thermal diffusivity Dper of 3.5 × 10-7 ± 0.5 m2 s-1. The value for thermal conductivity is comparable to the one measured on single cation perovskites, which is generally in the 0.2-0.6 range. The value for thermal diffusivity has not been reported previously.