Optimization of different ETL and BSF Layers with defects Management for high-performance CIGS solar cells

Abstract

In this work, we present a numerical investigation of the performance of CIGS based thin films solar cell by introducing different BSF and ETL materials. Employing SCAPS-1D simulation, we systemically analyzed the effects of the thickness, doping concentration Na and defects density (NT) of CIGS layer. The study revealed that the suitable incorporation of BSF and ETL was obtained for CBTS and SnSe2 respectively. The optimization of CIGS thickness from 0.2 µm to 1 µm, showed a critical influence on light absorption and carrier transport, with the efficiency rising from 25.66% to a peak value of 32.04%. However, beyond 1 µm, the PCE tends to stabilize and even slightly decrease, reaching 31.29% at 3.5 µm. Moreover, the increase in doping concentration Na in CIGS layer, particularly from 10¹² cm-³ to 10¹⁸ cm-³ led to an increase in efficiency from 20.70% at low doping to 29.44% at 10¹⁸ cm-³. The increasing of defects density in absorber layer led also to a significant degradation in the overall performance of the solar cell. Additionally, the results clearly demonstrated that the CIGS/CBTS and SnS2/CIGS interfaces must be carefully engineered to minimize interfacial defect states. Maintaining Nt below 10¹³ cm^-3 is critical for preserving high Voc and overall device efficiency.