Photo Seebeck Effect of Air Stable MAPbI3

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With increasing interest in energy harvesting using heat as a next-generation eco-friendly energy source, organic-inorganic perovskite materials have emerged as promising materials for thermoelectric devices. In particular, the photo-Seebeck effect of halide perovskite materials has attracted attention due to their wide optical absorption spectrum and large diffusion length, depending on their composition. MAPbI3, a representative organic perovskite component, has been reported to have a Seebeck coefficient of only hundreds of µV/K. In this manuscript, we report a photo-Seebeck effect for bulk MAPbI 3 perovskite in which the magnitude of the Seebeck coefficient significantly increased by 700 µV/K under illumination with a green laser diode. An air-stable perovskite pellet was synthesized using the alcohol substitution synthesis method, and both the Seebeck coefficient and the photocurrent increased in air, proving that enhanced Seebeck coefficient is associated with the formation of excitons in MAPbI3. X-ray diffraction analysis found that the remnant PbI2 led to n/i>-type electronic transport characterized by a negative Seebeck coefficient. Photo-induced electron transfer from MAPbI3 to the PbI2-rich phase under illumination led to dedoping of electrons, to form an MAPbI3 pellet. The significant enhancement in the Seebeck coefficient was found to depend on the composition of the remnant PbI2, which alters the majority carrier type in the bulk MAPbI3.