title: Tailoring Photoelectrochemical Performance and Stability of Cu(In,Ga)Se2Photocathode via TiO2-Coupled Buffer Layers.
abstract: We report on the photoelectrochemical (PEC) performance and stability of Cu(In,Ga)Se2(CIGS)-based photocathodes for photocatalytic hydrogen evolution from water. Various functional overlayers, such as CdS, TiO2, ZnxSnyOz, and a combination of the aforementioned, were applied on the CIGS to improve the performance and stability. We identified that the insertion of TiO2overlayer on p-CIGS/n-buffer layers significantly improves the PEC performance. A multilayered photocathode consisting of CIGS/CdS/TiO2/Pt exhibited the best current-potential characteristics among the tested photocathodes, which demonstrates a power-saved efficiency of 2.63%. However, repeated linear sweep voltammetry resulted in degradation of performance. In this regard, we focused on the PEC durability issues through in-depth chemical characterization that revealed the degradation was attributed to atomic redistribution of elements constituting the photocathode, namely, in-diffusion of Pt catalysts, out-diffusion of elements from the CIGS, and removal of the metal-oxide layers; the best-performing CIGS/CdS/TiO2/Pt photocathode retained its initial performance until the TiO2overlayer was removed. It was also found that the durability of CIGS photocathodes with a TiO2-coated metal-oxide buffer layer such as ZnxSnyOzwas better than those with a TiO2-coated CdS, and the degradation mechanism was different, suggesting that the stability of a CIGS-based photocathode can be improved by careful design of the structure.
authors.affiliation: Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST) , Daejeon 34141, Republic of Korea.
authors.forename: Bonhyeong
authors.initials: B
authors.lastname: Koo
authors.affiliation: Center for Nanomaterials and Chemical Reactions (CNCR), Institute for Basic Science (IBS) , Daejeon 34141, Republic of Korea.|Department of Molecular Medicine, School of Medicine, Kyungpook National University , Daegu 41404, Republic of Korea.
authors.forename: Sung-Wook
authors.initials: SW
authors.lastname: Nam
authors.affiliation: IBM T. J. Watson Research Center, Yorktown Heights, New York 10598, United States.
authors.forename: Richard
authors.initials: R
authors.lastname: Haight
authors.affiliation: Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST) , Daejeon 34141, Republic of Korea.
authors.forename: Suncheul
authors.initials: S
authors.lastname: Kim
authors.affiliation: Graduate School of Energy, Environment, Water, and Sustainability (EEWS), Korea Advanced Institute of Science and Technology (KAIST) , Daejeon 34141, Republic of Korea.
authors.forename: Seungtaeg
authors.initials: S
authors.lastname: Oh
authors.affiliation: Graduate School of Energy, Environment, Water, and Sustainability (EEWS), Korea Advanced Institute of Science and Technology (KAIST) , Daejeon 34141, Republic of Korea.
authors.forename: Minhyung
authors.initials: M
authors.lastname: Cho
authors.affiliation: Graduate School of Energy, Environment, Water, and Sustainability (EEWS), Korea Advanced Institute of Science and Technology (KAIST) , Daejeon 34141, Republic of Korea.
authors.forename: Jihun
authors.initials: J
authors.lastname: Oh
authors.affiliation: Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST) , Daejeon 34141, Republic of Korea.|Center for Nanomaterials and Chemical Reactions (CNCR), Institute for Basic Science (IBS) , Daejeon 34141, Republic of Korea.
authors.forename: Jeong Yong
authors.initials: JY
authors.lastname: Lee
authors.affiliation: Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST) , Daejeon 34141, Republic of Korea.
authors.forename: Byung Tae
authors.initials: BT
authors.lastname: Ahn
authors.affiliation: Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST) , Daejeon 34141, Republic of Korea.
authors.forename: Byungha
authors.identifier: http://orcid.org/0000-0001-6845-0305
authors.initials: B
authors.lastname: Shin
keywords: Cu(In,Ga)Se2 photocathode; overlayer; photoelectrochemical hydrogen evolution; solar water splitting; stability