Cost effective and “high” power conversion efficiency ultra-thin film GaAs solar cell

Abstract

In this paper we have designed and optically simulated a cheaper and flexible ultra-thin film GaAs solar cell having active layer thickness of ∼0.5 micron, even less than the GaAs cell with highest conversion efficiency (∼3 micron). The structure consists of an anti-reflection coating (ARC), n-type and p-type GaAs active layers. A combination of back reflecting pyramidal structure of Aluminium-Titanium alloy (AlTi) and a photonic crystal (Ge rods in SiO2) is used in order to increase the optical path length of the incident light and reflect back the desired portion of the incident spectrum back to the active region to enhance absorption. The cell structure is simulated using FDTD algorithm. Analysis of optical characteristics is done and found that the efficiency has crossed the Shockley Queisser (SQ) limit by ∼6%. Reduction in the thickness of active layer and the use of Aluminium-Titanium as textured back contact has made the cell cost effective.