Optimization of optical absorption and transport layer effects on Perovskite/ACIGS tandem solar cells

This study presents a comprehensive numerical investigation of two-terminal (2T) perovskite/ACIGS tandem solar cells using Silvaco TCAD tools, aiming to guide the design of high-efficiency tandem configuration. The subcells were calibrated based on data from experimentally fabricated perovskite and ACIGS devices, with a band-to-band tunneling junction employed to enable efficient carrier recombination. Despite successful stacking, the tandem configuration exhibits a V_oc loss of ∼28 mV before subcells matching, attributed to interfacial limitations in the top subcell. To address this, we explored the interplay of optical transparency, defect passivation, and charge transport by (1) selecting perovskite materials with tailored optoelectronic properties and thickness profiles, and (2) optimizing the electron transport layer (ETL) to minimize interfacial trap density and enhance charge extraction. Our optimized tandem structure achieves a simulated power conversion efficiency of 30.71 %, with a J_sc of 18.51 mA/cm², a V_oc of 2.05 V, and an FF of 80.97 %. The device further demonstrates enhanced thermal stability, with improved temperature coefficients for voltage (−0.164 %K⁻¹), current (−3.85 × 10⁻⁶ %K⁻¹), and power (−0.183 %K⁻¹), outperforming baseline models and silicon references. Comparative benchmarking confirms the effectiveness of the proposed strategy. This work not only advances predictive modeling of tandem photovoltaics but also offers actionable insights for overcoming interfacial and optical bottlenecks, paving the way for next-generation high-performance solar technologies.