title: BiVO4/WO3/SnO2Double-Heterojunction Photoanode with Enhanced Charge Separation and Visible-Transparency for Bias-Free Solar Water-Splitting with a Perovskite Solar Cell.
abstract: Coupling dissimilar oxides in heterostructures allows the engineering of interfacial, optical, charge separation/transport and transfer properties of photoanodes for photoelectrochemical (PEC) water splitting. Here, we demonstrate a double-heterojunction concept based on a BiVO4/WO3/SnO2triple-layer planar heterojunction (TPH) photoanode, which shows simultaneous improvements in the charge transport (∼93% at 1.23 V vs RHE) and transmittance at longer wavelengths (>500 nm). The TPH photoanode was prepared by a facile solution method: a porous SnO2film was first deposited on a fluorine-doped tin oxide (FTO)/glass substrate followed by WO3deposition, leading to the formation of a double layer of dense WO3and a WO3/SnO2mixture at the bottom. Subsequently, a BiVO4nanoparticle film was deposited by spin coating. Importantly, the WO3/(WO3+SnO2) composite bottom layer forms a disordered heterojunction, enabling intimate contact, lower interfacial resistance, and efficient charge transport/transfer. In addition, the top BiVO4/WO3heterojunction layer improves light absorption and charge separation. The resultant TPH photoanode shows greatly improved internal quantum efficiency (∼80%) and PEC water oxidation performance (∼3.1 mA/cm2at 1.23 V vs RHE) compared to the previously reported BiVO4/WO3photoanodes. The PEC performance was further improved by a reactive-ion etching treatment and CoOxelectrocatalyst deposition. Finally, we demonstrated a bias-free and stable solar water-splitting by constructing a tandem PEC device with a perovskite solar cell (STH ∼3.5%).
authors.affiliation: School of Advanced Materials Science & Engineering, Sungkyunkwan University , Suwon 440-746, Korea.
authors.forename: Ji Hyun
authors.initials: JH
authors.lastname: Baek
authors.affiliation: School of Advanced Materials Science & Engineering, Sungkyunkwan University , Suwon 440-746, Korea.
authors.forename: Byeong Jo
authors.initials: BJ
authors.lastname: Kim
authors.affiliation: Department of Mechanical Engineering and Materials Science, University of Pittsburgh , Pittsburgh, Pennsylvania 15261, United States.
authors.forename: Gill Sang
authors.initials: GS
authors.lastname: Han
authors.affiliation: Department of Materials Science & Engineering and Energy Systems Research, Ajou University , Suwon 443-749, Korea.
authors.forename: Sung Won
authors.initials: SW
authors.lastname: Hwang
authors.affiliation: School of Mechanical Engineering, Hanyang University , Seoul 133-791, Korea.
authors.forename: Dong Rip
authors.initials: DR
authors.lastname: Kim
authors.affiliation: Department of Materials Science & Engineering and Energy Systems Research, Ajou University , Suwon 443-749, Korea.
authors.forename: In Sun
authors.identifier: http://orcid.org/0000-0001-5622-7712
authors.initials: IS
authors.lastname: Cho
authors.affiliation: School of Advanced Materials Science & Engineering, Sungkyunkwan University , Suwon 440-746, Korea.
authors.forename: Hyun Suk
authors.initials: HS
authors.lastname: Jung
keywords: BiVO4/WO3/SnO2; charge transport; double-heterojunction photoanode; tandem PEC device; transmittance