Identifying the Ground-State NP Sheet through a Global Structure Search in Two-Dimensional Space and Its Promising High-Efficiency Photovoltaic Properties

Recently fabricated two-dimensional (2D) black phosphorene (BP) is considered to be a promising optoelectronic sheet, but its applications are hindered by the poor stability in air. Thus, it is desirable to investigate other BP-like 2D materials, which may have improved stability, while preserving the exceptional electronic properties of BP. Herein, using an efficient structure search method, we predicted a novel 2D BP-like material, namely, a honeycomb NP sheet (alpha-NP). Remarkably, its few-layer alpha-NP sheets possess not only a tunable direct bandgap under in-plane strain but also high mobility (X10(4) cm(2) v(-1) s(-1)) and absorption coefficients (X10(5) cm(-1)). These advantageous characteristics endow the alpha-NP sheets as a very potential 2D material for efficient photovoltaic cell applications, as demonstrate by an estimated photovoltaic efficiency of similar to 44%, when its thickness is at similar to 4 mu m. When combined with 2D MoTe2, it can provide a type-II heterojunction solar cell with a conversion efficiency up to similar to 16%. We also proposed a feasible strategy for mechanical cleavage to prepare the alpha-NP sheets from its bulk NP compound. Once prepared, the alpha-NP sheets may offer superior photovoltaic properties and facilitate the development of solar cells and optoelectronic devices.