Numerical Simulation of Lead-Free Tin and Germanium Based All Perovskite Tandem Solar Cell

Abstract

The ability to customize the materials bandgaps makes perovskite solar cells a promising candidate for hybrid-tandem applications. This allows them to effectively utilize parts of the solar spectrum that silicon-based solar cells cannot efficiently capture, resulting in higher absorption coefficients. However, there is a lack of research on lead-free all-perovskite tandem solar cells, and secondary data on materials is limited. One of the main challenges in previous studies is the high cost and solid structure of traditional silicon-based solar cells, which require significant storage space. Additionally, lead-based perovskite solar cells pose environmental concerns due to their water solubility and potential harmful effects upon consumption. To address these issues, thin-film perovskite solar cells with liquid solvents are employed in the solar cell design. Lead is replaced with germanium and tin-based perovskites, which exhibit comparable photovoltaic performance to silicon. In the present work, the OghmaNano simulation tool was utilized to conduct numerical simulation of the perovskite design. The perovskite solar cell layers were structured as follows: FTO/ZnO/MAGeI₃/Spiro-OMeTAD/FAMASnGeI₃/Cu₂O/Au. The variables considered included optimum layer thicknesses and bandgaps, as well as the most suitable materials for the ETL and HTL, aiming to obtain the highest efficiency. Based on the simulation results, the proposed perovskite structure shows remarkable photovoltaic parameters. The Voc was measured at 0.84 V Jsc of 16.1 mA/cm², FF of 0.825, and PCE that reached 11.12%. This project contributes to future research on materials for the ETL and HTL of lead-free, tin and germanium based APTSCs.