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Journal Article
Behavior of Photocarriers in the Light-Induced Metastable State in the p-n Heterojunction of a Cu(In,Ga)Se2 Solar Cell with CBD-ZnS Buffer Layer
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- Authors
- Woo-Jung Lee, Hye-Jung Yu, Jae-Hyung Wi, Dae-Hyung Cho, Won Seok Han, Jisu Yoo, Yeonjin Yi, Jung-Hoon Song, Yong-Duck Chung
- Issue Date
- 2016-08
- Citation
- ACS Applied Materials & Interfaces, v.8, no.34, pp.22151-22158
- ISSN
- 1944-8244
- Publisher
- American Chemical Society(ACS)
- Language
- English
- Type
- Journal Article
- Abstract
- We fabricated Cu(In,Ga)Se2 (CIGS) solar cells with a chemical bath deposition (CBD)-ZnS buffer layer grown with varying ammonia concentrations in aqueous solution. The solar cell performance was degraded with increasing ammonia concentration, due to actively dissolved Zn atoms during CBD-ZnS precipitation. These formed interfacial defect states, such as hydroxide species in the CBD-ZnS film, and interstitial and antisite Zn defects at the p-n heterojunction. After light/UV soaking, the CIGS solar cell performance drastically improved, with a rise in fill factor. With the Zn-based buffer layer, the light soaking treatment containing blue photons induced a metastable state and enhanced the CIGS solar cell performance. To interpret this effect, we suggest a band structure model of the p-n heterojunction to explain the flow of photocarriers under white light at the initial state, and then after light/UV soaking. The determining factor is a p+ defect layer, containing an amount of deep acceptor traps, located near the CIGS surface. The p+ defect layer easily captures photoexcited electrons, and then when it becomes quasi-neutral, attracts photoexcited holes. This alters the barrier height and controls the photocurrent at the p-n junction, and fill factor values, determining the solar cell performance.
- KSP Keywords
- Ammonia concentration, Aqueous solution, Band structure, Barrier height(BH), CIGS solar cell, Chemical bath deposition(CBD), Deep acceptor, Defect layer, Fill factor(F.F.), Light soaking, Light-induced