Benefits of Low Electron-Affinity Material as the N-Type Layer for Cu(In,Ga)S 2 Solar Cell

Dwinanri Egyna, Kazuyoshi Nakada and Akira Yamada
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Dwinanri Egyna: Department of Electrical and Electronic Engineering, Tokyo Institute of Technology, Ookayama, Meguro-ku, Tokyo 152-8552, Japan
Kazuyoshi Nakada: Department of Electrical and Electronic Engineering, Tokyo Institute of Technology, Ookayama, Meguro-ku, Tokyo 152-8552, Japan
Akira Yamada: Department of Electrical and Electronic Engineering, Tokyo Institute of Technology, Ookayama, Meguro-ku, Tokyo 152-8552, Japan

Energies, 2021, vol. 15, issue 1, 1-15

Abstract: Despite the potential in single- and multi-junction solar cells application, research into the wide band gap CuIn 1 − x Ga x (Se 1 − y S y ) 2 or CIG(SSe) 2 solar cell material, with E g ≥ 1.5 e V , has yet to be extensively performed to date. In this work, we conducted a numerical study into the role of the n-type layers in CIG(SSe) 2 heterojunction solar cells, specifically concerning the maximum open-circuit voltage of the devices. In the first part of the study, we derived a new ideal open-circuit voltage equation for a thin-film heterojunction solar cell by taking into account the current contribution from the depletion region. The accuracy of the new equation was validated through a simulation model in the second part of the study. Another simulation model was also used to clarify the design rules of the n-type layer in a wide band gap CIG(SSe) 2 solar cell. Our work stressed the importance of a positive conduction band offset on the n-/p-type interface, through the use of a low electron affinity n-type material for a solar cell with a high open-circuit voltage. Through a precise selection of the window layer material, a buffer-free CIG(SSe) 2 design is sufficient to fulfill such conditions. We also proposed the specific roles of the n-type layer, i.e., as a passivation layer and selective electron contact, in the operation of CIGS 2 solar cells.

Keywords: CIGS 2 solar cells; thin-film heterojunction; open-circuit voltage; n-type layer; CuInGaS 2 (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2021
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