Investigations on Absorber Type and Junction Position of GaAs Solar Cells

Gan Li1, Hassanet Sodabanlu2, Meita Asami1, Kentaroh Watanabe2, Masakazu Sugiyama1,2, Yoshiaki Nakano1 1Dept. of Electrical Engineering and Information systems, the Univ. of Tokyo, Tokyo, Japan /2Research Center for Advanced Science and Technology, the Univ. of Tokyo., Tokyo, Japan

Recently, some of the best InGaP, GaAs, and InGaAs cells have adopted a rear-heterojunction (RHJ) structure, which is considered able to boost the open circuit voltage (Voc)  of a device by suppressing non-radiative Sah-Noyce-Shockley (SNS) recombination in the space-charge region compared with conventional front-junction (FJ) structure. However, no study has been conducted to systematically evaluate different structures regarding their effect on solar cell performance. This paper presents an investigation comparing GaAs solar cells with different structures grown by metal-organic vapor phase epitaxy (MOVPE). The impacts of absorber type and junction position are individually analyzed regarding the solar cell performance. The n-type absorber samples had enhanced Voc and radiative efficiency than the p-type absorber ones, indicating superior crystal quality of n-GaAs. Besides, front-heterojunction (FHJ) samples showed an all-around boosted current and voltage performance than RHJ ones that share the same type of absorber, refreshing our understanding of the role of RHJ structure. Based on the observations, A p-on-n FHJ structure using an n-GaAs absorber is recommended for high-performance solar cells.