Advanced space-charge-limited current model for analyzing fermi level shift in the bandgap of halide perovskites
Stevan Gavranović, Oldřich Zmeškal, Martin Weiter, J. Pospı́šil
Abstract
Understanding how charge carriers behave in semiconductors is key to improving next-generation optoelectronic devices. Here we introduce an advanced space-charge-limited current model that enables detailed extraction of mobility, charge carrier concentrations, and Fermi level position from voltage- and energy-dependent analysis. Applying this model to two promising halide perovskites, methylammonium lead bromide and methylammonium lead iodide, we observe a strong photoresponse, with significant increases in microscopic mobility and free carrier density under illumination. Interestingly, the behavior of trapped charges and Fermi level shifts differs between the two materials, revealing distinct transport mechanisms. This model offers a powerful tool for characterizing semiconductors and could accelerate the development of more efficient light-sensitive devices. Halide perovskites offer the prospect of developing photovoltaic devices with increased power conversion efficiency but a greater understanding of the mechanisms behind their charge transport properties is a necessity. Here, the authors report a space-charge-limited current analysis that they use to extract information about key parameters, such as charge carrier mobilities, that contribute to the current-voltage characteristics of two halide perovskites under light and dark conditions.