Inverted Configuration of Cu(In,Ga)S-2/In2S3 on 3D-ZnO/ZnSnO3 Bilayer System for Highly Efficient Photoelectrochemical Water Splitting

Introducing a zinc stannate, ZnSnO3 (ZTO), layer on hydrothermally grown 3D-zinc oxide (ZnO) nanosheet thin films has been proven to have a quenching effect on the photoluminescence emissions, indicating very slow recombination of photoinduced electron-hole pairs in photoelectrochemical water splitting (PEC) reactions. Motivated by this, the ZnO/ZTO bilayer system has been used as the electron transport layer for copper indium gallium sulfide (CIGS)-based photoelectrodes in PEC applications. Furthermore, the poor photoresistivity of CIGS has been improved via indium sulfide (In2S3) deposition. Consequently, the photoelectrode obtained from the inverted configuration, ZnO/ZTO/CIGS/In2S3, has generated a photo-current density of 6.4 mA cm(-2) at 0.4 V (vs Ag/AgCl), exceeding the performance of ZnO NS/CIGS/In2S3 photoelectrodes by three folds. The highest ABPE and IPCE efficiencies have been calculated as 4.2% and 57%, respectively. More importantly, two cost-effective nonvacuum techniques for large-scale thin film fabrications such as chemical bath deposition (CBD) and ultrasonic spray pyrolysis (USP) methods have been adopted to acquire photoelectrodes with inverted configurations providing an advantageous approach for low-cost photoelectrode design for sustainable energy production.