Germanium perovskite solar cells: Overcoming the lead toxicity challenge with enhanced efficiency

The environmental concerns surrounding Lead in perovskite solar cells limit their commercial use despite their high efficiency records. This study demonstrates that Germanium-based devices can exceed lead-based performance while eliminating toxicity risks. One-dimensional Solar Cell Capacitance Simulator (SCAPS-1D) simulations were used to optimize CH₃NH₃GeI₃ and CH₃NH₃PbI₃-based solar cells in planar n i p configurations through systematic variation of transport layers, doping levels, absorber thickness, defect densities, and back contacts. The Germanium-based device achieved a power conversion efficiency of 26.74% with 20 nm SnO₂ electron transport layer, 20 nm NiOₓ hole transport layer, 850 nm absorber thickness, and Platinum back contact. This configuration delivers an open circuit voltage of 1.822 V, current density of 15.940 mA/cm², and fill factor of 92.07%. The Lead-based cell reached 23.50% efficiency with MoO₃ as the hole transport layer. The Germanium device's higher voltage and fill factor overcome its lower current density, proving that lead-free perovskites can surpass conventional performance while offering environmental safety.