Zinc oxide (ZnO) nanostructures were synthesized in the form of nanoparticles, nanoflowers and nanourchins. Structural. electronic and optical characterization of the samples were done via standard techniques such as X-ray...

In this report, the growth of zinc oxide (ZnO) nanocrystals with various morphologies, nanoflower, nanosheet, and nanorod, on flexible stainless steel (SS) foils to be utilized as photoanodes in photoelectrochemical (PEC) solar cells has been presented. It has been aimed to provide flexibility and adaptability for the next generation systems with the incorporation of SS foils as electrode into PEC cells. Therefore, physical deformation tests have been applied to the prepared ZnO thin film photoanodes. These thin films have been thoroughly characterized before and after straining for better understanding the relationship between the morphology, straining effect and photoelectrochemical efficiency. We observed a notable increase in the maximum incident photon-to-current efficiency (IPCE) and durability of all ZnO photoelectrodes after straining process. The increase in IPCE values by 1.5 and 2.5 folds at 370 nm has been observed for nanoflower and nanorod morphologies, respectively after being strained. The maximum IPCE of 69% has been calculated for the ZnO nanorod structures after straining. Bending of the SS electrodes resulted in the more oriented nanorod arrays compared to its flat counterpart, which improved both the light absorption and also the photo-conversion efficiency drastically. The finite-difference time-domain simulations have also been carried out to examine the optical properties of flat and bent ZnO electrodes. Finally, it has been concluded that SS photoanodes bearing ZnO semiconducting material with nanoflower and nanorod morphologies are very promising candidates for the solar hydrogen generator systems in terms of efficiency, durability, flexibility, and lightness in weight.

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 photocurrent 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.

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