Investigation of the impact of the rear-dielectric/silver back reflector design on the optical performance of thin-film silicon solar cells by means of detached reflectors

Abstract

Thin-film silicon solar cells often rely on a metal back reflector separated from the silicon layers by a thin rear dielectric as a back reflector (BR) design. In this work, we aim to obtain a better insight into the influence of the rear-dielectric/Ag BR design on the optical performance of hydrogenated microcrystalline silicon (µc-Si:H) solar cells. To allow the application of a large variety of rear dielectrics combined with Ag BRs of diverse topographies, the solar cell is equipped with a local electrical contact scheme that enables the use of non-conductive rear dielectrics such as air or transparent liquids of various refractive indices n. With this approach, detached Ag BRs having the desire surface texture can be placed behind the same solar cell, yielding a direct and precise evaluation of their impact on the optical cell performance. The experiments show that both the external quantum efficiency and the device absorptance are improved with decreasing n and increasing roughness of the BR. Calculations of the angular intensity distribution of the scattered light in the µc-Si:H are presented. They allow for establishing a consistent picture of the light trapping in the solar cell. Copyright © 2013 John Wiley & Sons, Ltd.