Lead-free X2MgGeI6 (X = Rb, Cs) double perovskites for multi-functional energy applications: A DFT and SCAPS-1D Perspective

This research aims to explore cost-effective and eco-friendly stable lead-free double halide perovskites X₂MgGeI₆ (X = Rb, Cs) for renewable energy applications. All computations were performed using WIEN2k. The PBE-GGA was used to optimize crystal structure, and the TB-mBJ potential estimated electronic characteristics. The compound X₂MgGeI₆ (X = Rb, Cs) is tested for power conversion efficiency using SCAPS-1D. Thermodynamics and structural stability were assessed using molecular dynamics, negative formation energies, and tolerance factor calculations. Both Rb₂MgGeI₆ and Cs₂MgGeI₆ exhibit indirect semiconductor nature with energy band gaps of 1.5 and 1.495 eV. Due to their lower effective masses and exciton binding energies, and promising optical characteristics, the understudy compounds may be used in solar cells and optoelectronic devices. Photocatalytic properties make the investigated materials promising hydrogen splitting candidates for solar-powered water splitting. Moreover, X₂MgGeI₆ (X = Rb, Cs) has significant solar energy conversion potential, achieving (30–32)% power conversion efficiency (PCE).