Strain driven modulations in electronic, optical properties and photovoltaic efficiencies of 2D AH (A = Si, Ge) monolayers: An account from first-principles study

Two-dimensional SiH and GeH monolayers offer promising avenues towards photovoltaic materials due to their exceptional optical absorption and tunable electronic properties. This study employs first-principles density functional theory calculations to investigate the impact of strain on their electronic structure, optical characteristics, and photovoltaic efficiencies. Under ambient conditions, SiH exhibits an indirect band gap of 2.76 eV, while GeH presents a direct band gap of 1.53 eV. Comprehensive analyses reveal that GeH achieves a maximum photovoltaic efficiency of ∼25.04 %, significantly surpassing SiH's ∼3.13 %. Notably, applying a 2 % tensile strain induces a transition in SiH from an indirect to a direct band gap semiconductor, whereas GeH maintains its direct band gap nature under both compressive and tensile strains. Optimal photovoltaic efficiencies are observed at tensile strains of 5 % for SiH (12.01 %) and 2 % for GeH (26.16 %). These findings highlight the potential of strained SiH and GeH monolayers in solar cell applications.