Beyond 22% power conversion efficiency in type-II MoSi2As4/MoGe2N4 photovoltaic vdW heterostructure

Abstract

Nowadays, substantial progress has been achieved in developing advanced solar cell materials, including high-performance two-dimensional (2D) materials like chalcogenides, perovskites, and oxides, along with their van der Waals (vdW) heterostructures. These efforts target enhanced photovoltaic efficiency, cost reduction, and reduced environmental impact. Despite this, challenges remain in improving light absorption, carrier mobility, and power conversion efficiency (PCE), highlighting the need for materials with enhanced optoelectronic properties. Here, we build a 2D MoSi₂As₄/MoGe₂N₄ vdW heterostructure with a 3.39 Å layer spacing, featuring an indirect band gap of 1.14 eV and type-II band alignment. Computational assessments demonstrate that photo-generated electrons efficiently transfer from the MoSi₂As₄ to the MoGe₂N₄ layer, while holes move in the opposite direction, reducing electron–hole recombination. The heterostructure exhibits excellent stability and optical absorption, with absorption coefficients up to 10⁵ cm⁻¹ across an extensive spectral range from visible to ultraviolet light. Furthermore, it also showcases an impressive electron mobility of 9065 cm² V⁻¹ s⁻¹ and a minimal conduction band offset of 0.05 eV, both of which contribute to an enhanced PCE, reaching up to 22.09%. These results position the MoSi₂As₄/MoGe₂N₄ heterostructure as a promising candidate for solar cell applications due to its superior optoelectronic properties.