Transparent Conductive Oxides Nanostructural Materials For Applications To Photoelectrochemistry

A method for fabricating high quality photonic TCO（transparent conductive oxide）films of macroporous FTO（fluorine doped tin oxide）（mac-FTO）is described.The films were used as electrodes to support photoelectrochemical reactions relevant to energy research.Planar FTO films coated on borosilicate glass and quartz synthesised in this chapter exhibit low sheet resistance（7.6Ω/□）and high transmittance over 85%,making them suitable substrates for supporting structured photonic crystals or photocatalysts.Polystyrene sphere template films with good optical and mechanical quality were deposited on these conductive substrates for preparing 3DOM TCOs.In comparison to a planar electrode,the photonic properties and the enhanced surface area per geometric area exhibit potential to improve the efficiency of photocurrent generation.The mac-FTO films described here are approximately 7μm thick.In addition,the mac-FTO films made by the improved method exhibits much better optical properties when compared with previous reports.Previous literature describing photonic mac-FTO films generally show poor conductivity and optical properties,which limit the performance of structured TCOs in supporting photoelectrochemistry.Pre-soaking the mac-FTO electrodes in OA,followed by deposition of nan-CdS dispersion was found to enhance the loading but decrease the homogeneity.Alternatively,the mac-FTO without OA stabilizer exhibits a homogenous coating but poor infiltration of the CdS nanoparticles.During the calcination,the lig ands were burned off from the nan-CdS@mac-FTO and an enhancement of photocurrent generation was observed.For improvement,decoration of CdS onto mac-FTO through the SILAR method was optimized by controlling the dipping cycles in CdS precursor solutions and the loading of the CdS is tuneable.The homogeneity of the nanoparticles coating was evidenced by electron microscopy and no significant aggregation was observed when using suitable dipping cycles.The shifted stop band position of mac-FTO electrodes were observed by DRUVS which is dependent on the loading level of CdS.The CdS loading was confirmed by EDX analysis and weighing the sample before and after the deposition.The amount of loading CdS in mac-FTO was significantly improved with high homogeneity.Optimizing the synthesis and processing conditions gives high quality optical and conductive films of mac-FTO.Coating films with dispersed nanoparticles of CdS shows that the mac-FTO supports charge carrier transport to the contact and is not just a structural support for continuous conductive films of photoactive materials.Coating to maximise photocurrent gives over 9 mA cm^-2 for conformally coated CdS@mac-FTO under visible light（>420 nm）through a simple approach,showing an improvement in comparison to previous CdS literature work on structured electrodes.