Influence of Density of States and Charge Carrier Mobility on the Performance of CdTe Thin-Film Solar Cells: A SCAPS-1D Study

Abstract

The performance of cadmium telluride (CdTe) thin-film solar cells is strongly influenced by intrinsic semiconductor properties such as carrier mobility and the effective density of states (DOS) in the conduction and valence bands. In this work, numerical simulations using the Solar Cell Capacitance Simulator in One Dimension (SCAPS-1D) were carried out to investigate the impact of electron and hole mobility (μₑ, μₕ) and effective density of states (Nc, Nv) on the photovoltaic performance of a standard CdTe/CdS heterojunction solar cell. Simulations were performed under standard test conditions (AM 1.5G spectrum, 1000 W m⁻², 300 K), with one parameter varied at a time while others remained fixed. Key output parameters analysed were open-circuit voltage (Voc), short-circuit current density (Jsc), fill factor (FF), and power conversion efficiency (η). Results show that increasing the conduction- or valence-band density of states leads to a significant reduction in Voc, accompanied by a moderate increase in FF and nearly unchanged Jsc, resulting in a slight decline in overall efficiency. Increasing electron mobility enhances Jsc and FF due to improved carrier transport but slightly reduces Voc, producing minimal net efficiency change. In contrast, higher hole mobility improves Voc and overall efficiency with negligible impact on Jsc. Across all cases, Voc was identified as the dominant parameter governing efficiency variations. The findings highlight the complex trade-off between carrier transport enhancement and recombination losses in polycrystalline CdTe absorbers and provide guidance for optimizing material properties to achieve higher-efficiency CdTe thin-film solar cells.