Layer-Dependent Photoabsorption and Photovoltaic Effects in Two-Dimensional <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><mml:msub><mml:mi>Bi</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mrow><mml:mrow><mml:mi mathvariant="normal">O</mml:mi></mml:mrow></mml:mrow><mml:mn>2</mml:mn></mml:msub><mml:mi>X</mml:mi></mml:math> (<i>X</i> = <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><mml:mrow><mml:mrow><mml:mi mathvariant="normal">S</mml:mi></mml:mrow></mml:mrow></mml:math>, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><mml:mi>Se</mml:mi></mml:math>, and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><mml:mi>Te</mml:mi></mml:math>)
Hao Tang, Bowen Shi, Yangyang Wang, Chen Yang, Shiqi Liu, Ying Li, Ruge Quhe, Jing Lü
Abstract
Significant photoconductive effects are reported in emergent two-dimensional (2D) ${\mathrm{Bi}}_{2}{\mathrm{O}}_{2}\mathrm{Se}$. In this work, we investigate the layer-dependent photoresponse properties and photovoltaic effects of 2D ${\mathrm{Bi}}_{2}{\mathrm{O}}_{2}X$ (X = $\mathrm{S}$, $\mathrm{Se}$, and $\mathrm{Te}$) by first-principles calculations and quantum-transport simulation. The absorbance per layer increases with the decreasing layer number for high-frequency light, so the absorbance density of 2D ${\mathrm{Bi}}_{2}{\mathrm{O}}_{2}X$ can be elevated by decreasing the layer number. An outstanding open-circuit voltage (1.08 V) among 2D materials is found for the monolayer (ML) ${\mathrm{Bi}}_{2}{\mathrm{O}}_{2}\mathrm{Se}$ p-n junction. The computed responsivities of ML black phosphorous, ${\mathrm{Mo}\mathrm{S}}_{2}$, and ${\mathrm{W}\mathrm{Se}}_{2}$ p-n junctions through our methods are in good agreement with experiments. The ML ${\mathrm{Bi}}_{2}{\mathrm{O}}_{2}\mathrm{Se}$ and ${\mathrm{Bi}}_{2}{\mathrm{O}}_{2}\mathrm{Te}$ p-n junctions show responsivities of 16.8 and 13.6 mA/W, respectively, under AM1.5 sunlight; these values are higher than those of their extensively studied ML ${\mathrm{Mo}\mathrm{S}}_{2}$ (8.6) and ${\mathrm{W}\mathrm{Se}}_{2}$ (8.8) counterparts. The ${\mathrm{Bi}}_{2}{\mathrm{O}}_{2}\mathrm{Se}$ film and ${\mathrm{Bi}}_{2}{\mathrm{O}}_{2}\mathrm{S}$ p-n junctions also show higher responsivities than those of commercial $\mathrm{Si}$ and $\mathrm{Ga}\mathrm{As}$. Therefore, the 2D ${\mathrm{Bi}}_{2}{\mathrm{O}}_{2}X$ p-n junctions have prospective applications in photovoltaic devices.