Charge carrier transport in two-dimensional tin halide perovskite field-effect transistors
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Abstract
Metal halide perovskites as new-generation semiconducting materials have gained huge attention in the field of high-performance solar cells, light-emitting diodes, and detectors, because of their excellent properties such as large light absorption coefficient, high charge mobility, tunable bandgap, and cost-effective solution processability. Field-effect transistors (FETs) provide an ideal platform to investigate the reliable long-range charge carrier transport properties of perovskite semiconductors including the influence of interfaces and morphology. Nevertheless, the mixed ionic-electronic nature of metal halide perovskites makes their performance in transistors complex in nature, with many challenges being still open. One aspect of the problem is the severe ion migration due to the presence of loosely bound constituent ions in these ionic materials, which are known to screen the electric field in perovskite FET devices, leading to low device mobility and large dual-sweep hysteresis.
The focus of this dissertation is on the systematic investigation of the charge carrier transport properties of two-dimensional (2D) layered tin halide perovskite in FETs. 2D layered tin halide perovskites are promising active channel materials for FET applications since bulky organic cations can effectively inhibit the ion migration. To understanding the correlation between chemical structure of organic spacer cations, grain size, thin film morphology, molecular organization, ion migration and charge carrier transport in 2D tin halide perovskite, different approaches, including grain engineering, additive modification, and spacer cation tuning have been employed in FETs. Combined with experimental characterization and simulation, it is revealed that reducing the number of grain boundaries and suppressing tin oxidation are effective methods to boost the charge carrier transport and minimize the ionic defects, leading to the overall improved electrical parameters of FET devices. A subtle change in molecular structure of organic cations has a significant impact on the molecular organization, phases and film morphology, which in turn, govern charge transport properties in 2D tin halide perovskite FETs.