Absorption Enhancement for Black Phosphorus Active Layer Based on Plasmonic Nanocavity
In this letter, we propose a strategy to enhance absorption in the black phosphorus absorber based on a nanocavity structure. By introducing a porous silver layer, an enhanced broadband light absorption can be obtained in the spectral range of 520–820 nm. The optical characteristics of the black phosphorus absorptive layer are thoroughly analyzed by absorption spectra, electric intensity distribution, and power flow distribution. Numerical and analytical analysis revealed that the optical absorption of the black phosphorus layer with a porous silver layer can be enhanced by 50% and 396% at the resonant wavelength of 690 nm for p-polarized and s-polarized incidences, respectively, when compared to that without a silver layer. Furthermore, the short-circuit current density (<inline-formula><tex-math notation="LaTeX">$J_{{\rm{SC}}}$</tex-math></inline-formula>) was calculated for the proposed architecture. The peak value of <inline-formula><tex-math notation="LaTeX">$J_{{\rm{SC}}}$</tex-math> </inline-formula> was more than 18 mA/cm<sup>2</sup>. It is demonstrated that this super absorption structure could find important applications on plasmonic-assisted photovoltaic devices or other opto-electronic devices, which will promote the development of ultrathin on-chip energy harvesting and new thin-film active devices.