Optimizing world-record thin-film ACIGS solar cells with innovative 'hockey stick'-shaped GGI profile for tandem solar technology

In this study, we perform a comprehensive optimization of key parameters influencing the performance of ACIGS (Ag-doped Cu(In,Ga)Se₂) solar cells, focusing on the effects of deposition environment and techniques. Parameters such as absorber thickness, dopant concentration, electron affinity, bulk defect density, and interface trap density are analyzed using advanced TCAD simulations. A calibrated device model based on experimental data accounts for all relevant material properties and defect distributions. Our findings reveal that minimizing bulk and interface defects primarily induced by deposition conditions is critical to enhancing stability and performance. Under standard test conditions (AM1.5G, 25 °C), the reference and optimized ACIGS single-junction cells achieve power conversion efficiencies (PCEs) of 23.60 % and 25.80 %, respectively. Furthermore, under varying temperatures (20–90 °C) and illumination intensities (10–120 mW/cm²), the optimized cell demonstrates notable improvements: a 15 % enhancement in power temperature coefficient and a 22 % increase in voltage temperature coefficient. For tandem configurations, we pair the optimized ACIGS bottom cell featuring a double gallium grading profile with a perovskite top cell (bandgap ≈ 1.70 eV). This results in PCEs of 31.92 % and 32.39 % for tandem devices using ITO and band-to-band tunneling (B2BT) interconnections, respectively, under AM1.5G illumination. The results are benchmarked against recent studies, providing valuable insights into advanced strategies and the physical behavior of high-efficiency tandem perovskite/ACIGS solar cells.