Plasmonic and photonic enhancement of photovoltaic characteristics of indium-rich InGaN p-n junction solar cells.

Abstract

In this paper, we demonstrate via Finite-difference time-domain (FDTD) simulations that the performance of indium-rich InxGa1-xN (x = 0.6) p-n junction thin-film solar cells is improved by incorporating an integrated structure of a 2-dimensional (2D) array of ITO nanodiscs on the top surface and a 2D array of Ag nanodiscs in the active layer above the Ag back reflector of the solar cell. The bottom Ag nanodiscs primarily enhance the absorption of longer wavelengths by coupling incident light into surface plasmon resonance (SPR) and waveguide modes. The top ITO nanodiscs enhance the middle wavelengths (400 nm to 800 nm) by coupling the incident light to photonic modes in the active layer. Thus, the integrated structure of nanodisc arrays leads to a very high absorption in the active region in broad spectral range (> 0.85 for wavelengths lying between 350 nm and 800 nm), significantly increasing the short circuit current density (Jsc) and power conversion efficiency (PCE) of the solar cell. In the proposed solar cells, the geometries of the silver and ITO nanodiscs were optimized to obtain the maximum possible values of the Jsc. The highest enhancements in Jsc and PCE of ∼25% and ∼26%, respectively, were obtained in a solar cell containing the integrated structure of ITO and Ag nanodisc arrays. Moreover, the performance of these cells was examined under oblique light incidence and it was observed that the solar cells containing the integrated structure of nanodisc arrays have a significantly larger value of Jsc when compared to the cells having no nanostructures or having only the top ITO nanodisc array or only the bottom Ag nanodisc array.