Growth, characterization, and thin film transistor application of CH3NH3PbI3 perovskite on polymeric gate dielectric layers

Abstract

Methylammonium-based perovskite compounds are generally grown on conducting or semiconducting substrates for high performance solar cell applications. In this study, we explore the growth of these compounds on insulators and test for their field-effect transistor performance. The key challenge is to find a surface that favors the crystal growth of perovskites without compromising the adhesion of the crystals. A family of methacrylate-based polymers has been identified as the insulators. Onto these insulators, methylammonium lead iodide polycrystalline thin films were grown. Generally, we found that the crystal size in the perovskite layers is well-correlated with the surface hydrophobicity. More hydrophobic polymer layers favor the growth of larger crystals, but result in less favorable adhesion of the perovskite. Methacrylate polymers with a phenyl substituent can give better adhesion and crystal sizes despite their hydrophobic properties. Among the different insulating polymer layers, we found that poly(phenyl methacrylate) (PPhMA), a derivative of the common commercial plastic poly(methyl methacrylate) (PMMA), produces the best perovskite films. The molecular origin of these properties is discussed. To test the electronic properties of these films, we employed them for thin-film transistor applications. Under optimal conditions, the thin-film transistors fabricated on PPhMA produce the best device with an electron mobility of 0.4 cm² V⁻¹ s⁻¹. Our results are also supported by photothermal deflection spectroscopy investigations of the subgap optical absorptions of these films.