Metal chalcogenide nanofilm electrodes MX (M=Cd, Cu or others; X=S, Se or Te) are investigated in photoelectrochemical (PEC) as replacement for the more costly p-n photovoltaic junctions. However, such electrodes are unstable and yield low conversion efficiency. We developed simple strategies to enhance both stability and conversion efficiency for such electrodes. Attachment of electro-active species, embedded inside polymeric matrices, to the surface of the electrode permanently affects its photo-electrochemical (PEC) properties. The electro-active species behaves as charge transfer catalyst across the solid/liquid junction. This increases the charge (holes or electrons depending on the type of the SC) transfer rate between the electrode and the redox couple. The SC electrode can thus be stabilized to photo-degradation. The strategy has been effective for various nano-film electrodes (CuS, CuSe, CdSe, CdTe and others). Conversion efficiency is enhanced from ~1.0% to above 10%. Careful pre-annealing the electrodes, before coating, and controlled cooling rate, give extra enhancement in PEC characteristics. Pre-annealed electrodes, coated with electroactive materials inside polymer matrices, yield >18.0% conversion efficiency. The values are higher than US DOE expectation for 2020, and have not been reported earlier for metal chalcogenide film electrodes. This presentation will show a critical survey of our results observed throughout the last 20 years, as compared to literature. Our new model proposed for the efficiency and stability enhancement will also be rigorously presented. Future prospects of this work will also be discussed.
Key Words: Semiconductors; Thin Film Electrodes; Conversion Efficiency; Stability; Charge Transfer Catalysis.