Performance enhancement in CZTSSe solar cells via BaSi₂ back surface field integration

The efficiency of solar cells is strongly influenced by factors such as durability, cost-effectiveness, environmental compatibility, and overall performance. Recent advancements in kesterite-based CZTSSe solar cells have revealed a persistent challenge of low open-circuit voltage (V_OC), which significantly limits device efficiency. This work focuses on optimizing absorber and interface properties to enhance the simulated performance of CZTSSe solar cells. The thermal stability of the proposed structure is also evaluated by examining the effect of operating temperature on key photovoltaic parameters. To address performance limitations, a BaSi₂-based back surface field (BSF) layer is incorporated, and numerical simulations are carried out using the SCAPS-1D software. The introduction of the BaSi₂-based BSF layer effectively reduces V_OC-related losses and enhances the overall device efficiency. The model's validity is supported through comparison with previously published experimental and simulation data. Incorporating BaSi₂ as the BSF layer increases the simulated efficiency from 12.54% to 16.37%. In parallel, a systematic study of the CZTSSe absorber layer was conducted to determine the optimal thickness and doping concentration for further improving solar cell performance. The values can be varied systematically, such as the absorber's layer thickness from 0.5 to 3 μm, and the doping concentration is modified from 10¹² to 10¹⁸ cm^{- 3}. An efficiency of 19.61% can be achieved for the recently improved configuration using a CZTSSe thickness of just only 0.5 μm under idealized conditions but not experimentally realistic. This reduction of the thickness of the CZTSSe solar cells is an important factor in the decline of performance, but it can improve the lifetime of minority carriers.