Evaluation of the Thermoelectric Properties and Thermal Conductivity of CH3NH3PbI3-x Cl x Thin Films Prepared by Chemical Routes.

Abstract

The thermoelectric properties and thermal conductivity of mixed-phase CH3NH3PbI3–xClx thin films have been reported as a function of temperature, ranging from room temperature (RT) to 388 K. Thermoelectric study confirms that CH3NH3PbI3–xClx is a p-type material and the charge carrier transport in CH3NH3PbI3–xClx is governed by polarons and the thermal scattering process. The Peltier function and power factor are found to decrease initially up to ∼325 K, after which they increase with increasing temperature. The position of (EF – EV) of all samples drops down sharply to zero level around 325 K. The avalanches of thermoelectric properties at ∼325 K indicate the existence of tetragonal–cubic phase transition in CH3NH3PbI3–xClx. The calculated thermal conductivity is very low, as desired for thermoelectric materials, due to strong anharmonic interactions. Both the figure of merit (ZT) and device efficiency increase with increasing temperature. However, ZT remains small with temperature. Despite the limitations on the operating temperature range due to phase complexity and small ZT, CH3NH3PbI3–xClx exhibits reasonable thermoelectric power and low thermal conductivity. This signifies the possibility of CH3NH3PbI3–xClx as a prospective thermoelectric material.