Current Remedy in Ultrathin Crystalline Si Solar Cell by Cu₂SnS₃ Thin Film toward High Efficiency

Abstract

An ultrathin 15 μm wafer‐based c‐Si solar cell is designed and simulated, wherein the current remedy is done by Cu2SnS3 (CTS) thin film. The ZnSe and AlSb are incorporated as window and back surface field (BSF) layers, respectively, in this model. The ultrathin Si‐based n‐ZnSe/p‐Si exhibits the short‐circuit current density of 30.66 mA cm−2 with an efficiency of 18.80%. The inclusion of p+‐CTS thin film as a second absorber layer has enhanced this current to 42.14 mA cm−2. By absorbing sunlight up to 1200 nm, the CTS layer is able to successfully overcome the constraint of thinner Si wafers on longer‐wavelength photon absorption leading to current augmentation. The addition of p++‐AlSb as the BSF layer also boosts the open‐circuit voltage by 300 mV. The rise in VOC is a result of the larger built‐in potential in ZnSe/Si, Si/CTS, and CTS/AlSb interfaces. With enriched current and voltage, the final proposed n‐ZnSe/p‐Si/p+‐CTS/p++‐AlSb heterostructure theoretically records an efficiency of 35.48% in ultrathin Si solar cells. The current compensation obtained using CTS thin film in this work can give optimism about the future of ultrathin Si solar cells.