Substitutional doping of hybrid organic–inorganic perovskite crystals for thermoelectrics

Abstract

Hybrid organic–inorganic perovskites have generated considerable research interest in the field of optoelectronic devices. However, there have been significantly fewer reports of their thermoelectric properties despite some promising early results. In this article, we investigate the thermoelectric properties of bismuth-doped CH₃NH₃PbBr₃ (MAPbBr₃) single crystals. The high-quality Bi-doped crystals were synthesized by inverse temperature crystallization and it was found that Bi substitutes onto the B-site of the ABX₃ perovskite lattice of MAPbBr₃ crystals with very little distortion of the crystal structure. Bi doping does not significantly alter the thermal conductivity but dramatically enhances the electrical conductivity of MAPbBr₃, increasing the charge carrier density by more than three orders of magnitude. We obtained a negative Seebeck coefficient of −378 μV K⁻¹ for 15% (x = 0.15) Bi-doped MAPb_(1−x)Bi_xBr₃ confirming n-type doping and also measured the figure of merit, ZT. This work highlights routes towards controlled substitutional doping of halide perovskites to optimise them for thermoelectric applications.