Reflective Barrier Optimization in Ultrathin Single-Junction GaAs Solar Cell

Abstract

This paper proposes a theoretical analysis of electronic transport in ultrathin (220 nm) single-junction GaAs solar cell. Using an in-house electronic quantum transport model, we shed light on two detrimental phenomena, namely the “back-diffusion” and the “contact-to-contact diffusion.” While the back-diffusion degrades both the short-circuit current and the fill factor, the contact-to-contact diffusion reduces the open-circuit voltage. The so-called window and back-surface-field barriers used to reflect minority carriers away from contacts reduce these two detrimental phenomena. In a second part, we then show a synthesis of performance optimization of window/GaAs/back-surface-field heterojunctions varying thicknesses, materials, and material composition profiles. Our results conclude that the $\mathrm{\text{Al}_{0.4}\text{Ga}_{0.6}\text{As}(10\; nm)/\text{GaAs}/\text{In}_{0.49}\text{Ga}_{0.51}P(10\; nm)}$ structure provides the best output power.