Ordered transparent conductive oxides (TCOs) for applications to photoelectrochemistry

• Main Author: Zhang, Menglong
• Other Authors: Douthwaite, Richard
• Published: University of York 2016
• Subjects: 541
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.696079

A method for fabricating high quality photonic TCO (transparent conductive oxide) films of macroporous FTO (fluorine doped tin oxide) (mac-FTO) and hollow sphere AZO (aluminum doped zinc oxide) (hs-AZO) is described. The films were used as electrodes to support photoelectrochemical reactions relevant to energy research. Methods have been developed for conformal coating the TCO electrodes with photoactive materials including CdS, Fe2O3 and C3N4. Previous literature describing photonic mac-FTO films generally show poor conductivity and optical properties, which limit the performance of structured TCOs in supporting photoelectrochemistry. 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. The new hs-AZO TCO also supports photocurrents up to 7.8 mA cm-2 after CdS coating. Both FTO and AZO show significant photocurrent enhancement in comparison to planar FTO analogues. In addition to CdS, methods were developed to conformally coat the organic photocatalyst C3N4 and the metal oxide Fe2O3 onto mac-FTO which showed enhanced photocurrent compared to planar analogues. Enhancements were typically in the range x (CdS), y (C3N4), and z (Fe2O3) which reflect the increase in surface area and greater loading of photoactive material. Potential photonic enhancements were not determined, however there is clearly scope for increasing the photocurrent per illuminated surface area using structured TCO electrodes.