Improved charge transfer and photoelectrochemical performance of CuI/Sb2S3/TiO2 heterostructure nanotube arrays

Charge transfer is important for the performance of a photoelectrochemical cell. Understanding photogenerated charge accumulation and separation is mandatory for the design and optimisation of photoelectrochemical cells. Unique stacked and embedded heterostructure of Sb2S3/TiO2 nanotube arrays (NTAs) was fabricated through anodic oxidation with the hydrothermal method. Surface photovoltage spectroscopy, phase spectra and photoluminescence measurements were performed to explore the mechanism by which the inorganic hole transport material CuI affects the charge transfer and photoelectrochemical properties of Sb2S3/TiO2 heterostructure NTAs. The interfacial separation and transport of photoinduced charge carriers were also examined by applying current–voltage characteristics (J–V), incident-photon-to-current conversion efficiency (IPCE) and Mott–Schottky techniques. Results show that CuI acts not only as a hole-conducting and electron-blocking material but also as a light-absorbing material in the ultraviolet range. Efficient charge transfer processes exist in CuI/Sb2S3/TiO2 heterostructure NTAs. The photoelectrochemical performance of CuI/Sb2S3/TiO2 heterostructure NTAs is dramatically improved. Under AM 1.5G illumination at 100 mW/cm2, the short-circuit current density and open-circuit voltage are 3.51 mA/cm2 and 0.87 V, respectively. The photoelectric conversion efficiency of CuI/Sb2S3/TiO2 heterostructure NTAs (0.95%) is 36% higher than that of Sb2S3/TiO2 heterostructure NTAs (0.66%).

CuI provides channels for photogenerated holes and blocks electrons, thereby significantly decreasing the recombination of electron–hole pairs in Sb2S3. CuI/Sb2S3/TiO2 heterostructure NTAs demonstrate effective charge transport, high separation efficiency of photogenerated carriers and improved photoelectrochemical performance. Moreover, CuI/Sb2S3/TiO2 heterostructure NTAs could collect additional charge produced by CuI as large band gap hole conducting material that can absorb light in an ultraviolet region. The η of the CuI/Sb2S3/TiO2 heterostructure NTA electrode (0.95%) is 36% higher than that of the Sb2S3/TiO2 heterostructure NTAs (0.66%).Figure optionsDownload high-quality image (78 K)Download as PowerPoint slide