Nano-porous silicon photo-electrodes for solar fuel by using visible sunlight

Splitting of water using visible range band gap photo-electrodes for solar fuel such as hydrogen fuel is studied. Hydrogen is knowing for future fuel due to easily attainable and environment friendly behavior. Hydrogen can be extracted using sun light by photo-electrochemical (PEC) process, which is considered as one of the prominent method to split water thorough sun light.  To be more precise the band edges to decompose water into its molecules should be with appropriate band gap of 1.23 eV and on practicality ~1.9 to 2.0 eV is required. Porous silicon (PS) with band gap of approximately 2.0 eV is reported by showing suitability as per the requirement. Nano-porous formation was prepared on p-type silicon with low resistivity of about 1 Ω.cm. Electro-chemical etching was established for formation of PS with pores diameter of around 50 µm. To deal with the high resistance and dielectric surface behavior of PS different materials for example conductive polymers “poly-pyrrole, poly-aniline and ploy-thiophene”, conductive oxides “TiO₂” and graphene were studied, to be selected for the most suitable applicant to make PS surface applicable as photo-electrode for oxidation of water. The deposition of TiO₂ was investigated with different depths and overall PEC process was carried out by using Pt wire as counter electrode. The inclusive analysis applied thorough measuring the current over the period of time and observed the uniformity of the pores on the silicon sample through various characterization techniques. The results showed good stability with proper band gap and morphology of porous structure. The whole study object was to carry out the comparative analysis by considering different morphologies of PS, to be most suitable for further prospective, to utilize the maxima of PS properties such as quantum confinement effect, stability, suitable band gap etc. The further analysis are to achieve higher current densities, which could lead to higher Solar to Hydrogen (STH) efficiency.