Highly Transparent and Stable N-Type Protective Layers for Spray Pyrolyzed CuO Thin Films for Photoelectrochemical Energy Conversion- a Comparative Study

Various inexpensive and highly transparent n-type semiconducting oxides (ZnO, NiO, BaSnO3, Fe2O3, and Al2O3) are tested for their possible application as a protective layer on CuO photocathode. All the above films are synthesized by a highly scalable chemical spray pyrolysis technique. Optimized thin layers show high charge carrier concentration 1011- 1017 /cm3 and excellent electron mobility, improved charge separation capability. All of them show large and stable photocurrent density of CuO thin film photocathode when used as a protective layer. Time-Resolved Photoluminescence (TRPL) is measured to understand the carrier lifetime in them. The photo-electrochemical behavior of all electrodes is performed in the dark and illumination with neutral (pH ~8) and alkaline (pH ~14) electrolytes. Photostability of all prepared heterojunctions ZnO/CuO, NiO/CuO, BaSnO3/CuO, Fe2O3/CuO, and Al2O3/CuO photocathodes are measured under continuous AM 1.5 G illumination for 300 s. Comparative study of solar to chemical conversion efficiency of fabricated photocathodes are presented.