BiVO4/WO3/SnO2 Double-Heterojunction Photoanode with Enhanced Charge Separation and Visible-Transparency for Bias-Free Solar Water-Splitting with a Perovskite Solar Cell

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• 作者：Ji Hyun Baek ; Byeong Jo Kim ; Gill Sang Han ; Sung Won Hwang ; Dong Rip Kim ; In Sun ChoHyun Suk Jung
• 刊名：ACS Applied Materials & Interfaces
• 出版年：2017
• 出版时间：January 18, 2017
• 年：2017
• 卷：9
• 期：2
• 页码：1479-1487
• 全文大小：641K
• ISSN：1944-8252

文摘

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 BiVO<sub>4sub>/WO<sub>3sub>/SnO<sub>2sub> triple-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 SnO<sub>2sub> film was first deposited on a fluorine-doped tin oxide (FTO)/glass substrate followed by WO<sub>3sub> deposition, leading to the formation of a double layer of dense WO<sub>3sub> and a WO<sub>3sub>/SnO<sub>2sub> mixture at the bottom. Subsequently, a BiVO<sub>4sub> nanoparticle film was deposited by spin coating. Importantly, the WO<sub>3sub>/(WO<sub>3sub>+SnO<sub>2sub>) composite bottom layer forms a disordered heterojunction, enabling intimate contact, lower interfacial resistance, and efficient charge transport/transfer. In addition, the top BiVO<sub>4sub>/WO<sub>3sub> heterojunction 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/cm<sup>2sup> at 1.23 V vs RHE) compared to the previously reported BiVO<sub>4sub>/WO<sub>3sub> photoanodes. The PEC performance was further improved by a reactive-ion etching treatment and CoO<sub>xsub> electrocatalyst 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%).