Two-Dimensional Halide Perovskite Materials Featuring 2-(Methylthio)ethylamine Organic Spacers for Efficient Solar and Thermal Energy Harvesting

Two-dimensional (2D) halide-based hybrid perovskites are recognized as emerging materials for solar cells and thermoelectric applications. Here, we report on the electronic, optical, and thermoelectric properties of the 2-(methylthio)ethylamine (MTEA)-based 2D perovskites (MTEA)2PbI4 and (MTEA)2(MA)Pb2I7 using density functional theory calculations. The Rashba-splitting strength is observed to lie between 0.41 and 0.65 eV angstrom at four positions of the band structure of (MTEA)2(MA)Pb2I7. The strong sulfur-sulfur interaction between MTEA spacers results in a noticeable shift in the onset of the absorption spectrum. For (MTEA)2(MA)Pb2I7, a larger theoretical limit in the power conversion efficiency (29%) is calculated compared to (MTEA)2PbI4, which can be attributed to the absorption coefficient difference in both structures. The considered structures show very small effective electron masses, which results in an exceptionally high electron carrier mobility. The calculations yield an extremely large thermoelectric power factor of 42.3 mW/mK2 for (MTEA)2(MA)Pb2I7 at 300 K, which is even higher than that of 3D and 2D perovskites reported so far. The present work suggests that the (MTEA)-based 2D perovskites are promising candidates for application in solar-and thermal-energy harvesting.