In this work we have synthesized the colloidal particles of transition metal-hydroxide (M= Ni, Co, Mn, Fe) by a simple chemical precipitation method. The surface of spray deposited CdS thin films were modified using nano-colloids to utlize them as water oxidation catalysts (WOC) for the photoelectrochemical cell (PEC). A systematic comparison of the PEC performance of modified and unmodified film is carried out to understand the role of co-catalyst. Ni(OH)2 modification yields 3.4 times higher photocurrent density than bare CdS photoanode, and exhibits hydrogen-evolution rate of 600 μmol/hr. Fe(OH)2 modified film shows best stability of 8 hours as compared to the others.

Titanium oxide photoelectrodes have been used for water splitting for a few decades, but have low solar-to-hydrogen efficiencies. Perovskite halides (e.g., CH3NH3PbI3) have recently emerged as an efficient light absorber system. We try to combine the two materials to create new photoelectrodes to achieve a higher efficiency for hydrogen production. The photoelectrodes are investigated for water-splitting hydrogen production under Xe light irradiation by photoelectrochemical (PEC) reaction. Since perovskite halides are favorable light harvesters under UV and visible light irradiation, the composite films of titania and perovskite halide would achieve efficient water splitting. The hydrogen production rate using the composite films is higher than that using anatase TiO2 electrode. However, the composite films are not stable in water under light irradiation and the perovskite halide gradually decomposes into lead halide.

Our investigations with silane-modified TiO2 have revealed a beneficial effect of functionalization on the photoelectrochemical performance on spin-coated electrodes. However, in order to produce large area photoelectrodes, a more scalable manufacturing technology is required. Inkjet printing can fulfil this role and furthermore allow a finer control over coating morphologies. In this work, inkjet-printed photoelectrodes were prepared with silane-functionalized TiO2 nanoparticles, and investigated as electrodes for photoactivated water splitting. The catalyst layers, having thickness around 700 nm, were printed on FTO-coated glass supports, from cellulose stabilized dispersions. For comparison, electrodes of similar thicknesses were also prepared by spin-coating. After removing the stabilizer at 300 °C under air atmosphere, the electrodes were characterized in photoelectrochemical cells containing 0.5 M H2SO4 as electrolyte and a platinum ring as counter electrode. Under simulated sunlight, the best photocurrent densities for the oxygen evolution reaction were obtained for the inkjet-printed electrodes prepared with functionalized particles (up to 0.26 mA cm-2 at 1.2 V against the standard hydrogen electrode (SHE), compared to 0.18 mA cm-2 for spin coated). Microscopy of the printed electrodes shows structurally homogenous coatings with evenly distributed roughness. Under continuous illumination at 0.7 V (SHE), the electrodes showed no significant drop in photocurrent within five hours.

Today’s conversion of solar energy into electricity is based on silicon, which is pure, eventually crystalline, and its most efficient transitions are away from solar radiation maximum. The continuous search of efficient photovoltaic materials has recently focused on lead-halide organic-inorganic perovskite materials due to the very flexible, sustainable, and forgiving procedure of their fabrication, which is successful even if the concentrations of precursors, and temperature regimes deviate from optimal values. In addition to simple fabrication, this class of materials provides impressively high efficiency of photovoltaic (PV) cells. Attention to these materials helps to understand the mechanisms of their high efficiencies and to identify other materials with same type of properties. This work presents computational analysis of photo-induced processes in perovskite materials at ambient temperatures.