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학술지 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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이우정, 유혜정, 위재형, 조대형, 한원석, 유지수, 이연진, 송정훈, 정용덕
ACS Applied Materials & Interfaces, v.8 no.34, pp.22151-22158
American Chemical Society(ACS)
16PB2200, 초경량 유연 CIGS 박막 모듈 공정장비 상용화 기술개발, 정용덕
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.
chemical bath deposition, Cu(In,Ga)Se 2, defect layer, light/UV soaking effect, p-n heterojunction, photocarriers
KSP 제안 키워드
Ammonia concentration, Aqueous solution, CIGS solar cell, Chemical bath deposition(CBD), Deep acceptor, Defect layer, Light soaking, Light-induced, P-N junction, Petri net(PN), Photoexcited electrons