Hybrid halide perovskites have recently received exponential interest due to their extraordinary photovoltaic performances. Apart from solar cells, multitude of other applications such as photodetectors, lasers, LEDs, and memory devices have been already demonstrated underpinning the versatile nature of halide perovskites. Despite the unprecedented performance of hybrid perovskites, their other crucial physical properties such as thermal transports have received limited attention. The majority of the works on thermal transport of hybrid perovskites are accomplished using single crystals or polycrystalline pellets with limited information on seebeck coefficient. Furthermore, in-plane thermal conductivity and seebeck coefficient of CH3NH3PbI3 films remains largely unexplored. Thermal transport behaviors strongly correlate with material structure and its meticulous understanding is imperative for thermal management of efficient and high performance devices. In this work, we systematically investigate the thermal conductivity and thermopower of sequential vapor deposited CH3NH3PbI3 films. An ultralow in-plane thermal conductivity of 0.3 Wm-1K-1 at room temperature was recorded for CH3NH3PbI3 using a chip-based 3ω method. Temperature-dependent thermal conductivity measurement of a series of CH3NH3PbI3 films with different degree of methylammonium treatment reveal that the thermal conductivity value is governed by PbI6 octahedron framework. Furthermore, n- and p-type CH3NH3PbI3 films were achieved by compositional tuning of the precursors (CH3NH3I and PbI2) resulting in high negative and positive thermopower. The effect of self-doping and defects on the thermopower along with the implications of the present work on future thermoelectrics based on hybrid perovskites will be discussed.
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