title: Photovoltaic Performance and Interface Behaviors of Cu(In,Ga)Se2 Solar Cells with a Sputtered-Zn(O,S) Buffer Layer by High-Temperature Annealing.
abstract: We selected a sputtered-Zn(O,S) film as a buffer material and fabricated a Cu(In,Ga)Se2 (CIGS) solar cell for use in monolithic tandem solar cells. A thermally stable buffer layer was required because it should withstand heat treatment during processing of top cell. Postannealing treatment was performed on a CIGS solar cell in vacuum at temperatures from 300-500 °C to examine its thermal stability. Serious device degradation particularly in VOC was observed, which was due to the diffusion of thermally activated constituent elements. The elements In and Ga tend to out-diffuse to the top surface of the CIGS, while Zn diffuses into the interface of Zn(O,S)/CIGS. Such rearrangement of atomic fractions modifies the local energy band gap and band alignment at the interface. The notch-shape induced at the interface after postannealing could function as an electrical trap during electron transport, which would result in the reduction of solar cell efficiency.
authors.affiliation: †Electronics and Telecommunications Research Institute (ETRI), 218 Gajeong-ro, Yuseong-gu, Daejeon 305-700, Republic of Korea.
authors.forename: Jae-Hyung
authors.initials: JH
authors.lastname: Wi
authors.affiliation: ‡Korea University of Science and Technology (UST), 217 Gajeong-ro, Yuseong-gu, Daejeon 305-350, Republic of Korea.|§Korea Research Institute of Standards and Science (KRISS), 267 Gajeong-ro, Yuseong-gu, Daejeon 305-340, Republic of Korea.
authors.forename: Tae Gun
authors.initials: TG
authors.lastname: Kim
authors.affiliation: ‡Korea University of Science and Technology (UST), 217 Gajeong-ro, Yuseong-gu, Daejeon 305-350, Republic of Korea.|§Korea Research Institute of Standards and Science (KRISS), 267 Gajeong-ro, Yuseong-gu, Daejeon 305-340, Republic of Korea.
authors.forename: Jeong Won
authors.initials: JW
authors.lastname: Kim
authors.affiliation: †Electronics and Telecommunications Research Institute (ETRI), 218 Gajeong-ro, Yuseong-gu, Daejeon 305-700, Republic of Korea.
authors.forename: Woo-Jung
authors.initials: WJ
authors.lastname: Lee
authors.affiliation: †Electronics and Telecommunications Research Institute (ETRI), 218 Gajeong-ro, Yuseong-gu, Daejeon 305-700, Republic of Korea.
authors.forename: Dae-Hyung
authors.initials: DH
authors.lastname: Cho
authors.affiliation: †Electronics and Telecommunications Research Institute (ETRI), 218 Gajeong-ro, Yuseong-gu, Daejeon 305-700, Republic of Korea.
authors.forename: Won Seok
authors.initials: WS
authors.lastname: Han
authors.affiliation: †Electronics and Telecommunications Research Institute (ETRI), 218 Gajeong-ro, Yuseong-gu, Daejeon 305-700, Republic of Korea.|‡Korea University of Science and Technology (UST), 217 Gajeong-ro, Yuseong-gu, Daejeon 305-350, Republic of Korea.
authors.forename: Yong-Duck
authors.initials: YD
authors.lastname: Chung
keywords: Cu(In,Ga)Se2; Zn(O,S); bottom cell; depth profiling; energy band alignment; thermal annealing