Microwave-assisted low temperature fabrication of ZnO thin film electrodes for solar energy harvesting

• Published in: Thin solid films Vol. 590; pp. 293 - 298
• Main Authors: Nirmal Peiris, T.A., Sagu, Jagdeep S., Hazim Yusof, Y., Upul Wijayantha, K.G.
• Format: Journal Article
• Language: English
• Published: 01-09-2015
• Subjects: Annealing; Electrodes; Microwaves; Photocurrent; Photoelectric effect; Thin films; Zinc; Zinc oxide
• ISSN: 0040-6090
• DOI: 10.1016/j.tsf.2015.08.008

Metallic Zn thin films were electrodeposited on fluorine-doped tin oxide (FTO) glass substrates and oxidized under air by conventional radiant and microwave post-annealing methods to obtain ZnO thin film electrodes. The temperature of each post-annealing method was varied systematically and the photoelectrochemical (PEC) performance of electrodes was evaluated. The best photocurrent density achieved by the conventional radiant annealing method at 425 degree C for 15min was 93 mu Acm-2 at 1.23V vs. NHE and the electrode showed an incident photon-to-electron conversion efficiency (IPCE) of 28.2%. X-ray diffractogram of this electrode showed that the oxidation of Zn to ZnO was not completed during the radiant annealing process as evident by the presence of metallic Zn in the electrode. For the electrode oxidized from Zn to ZnO under microwave irradiation, a photocurrent of 130 mu Acm-2 at 1.23V vs. NHE and IPCE of 35.6% was observed after annealing for just 3min, during which the temperature reached 250 degree C. The photocurrent was 40% higher for the microwave annealed sample; this increase was attributed to higher surface area by preserving the nanostructure, confirmed by SEM surface topographical analysis, and better conversion yields to crystalline ZnO. Overall, it was demonstrated that oxidation of Zn to ZnO can be accomplished by microwave annealing five times faster than that of conventional annealing, thus resulting in a ~75% power saving. This study shows that microwave processing of materials offers significant economic and performance advantages for industrial scale up.