Copper selenide film electrodes prepared by combined electrochemical/chemical bath depositions with high photo-electrochemical conversion efficiency and stability

Copper selenide (of the type Cu2-xSe) film electrodes, prepared by combined electrochemical (ECD) followed by chemical bath deposition (CBD), may yield high photo-electrochemical (PEC) conversion efficiency (~14.6%) with no further treatment. The new ECD/CBD-copper selenide film electrodes show enhanced PEC characteristics and exhibit high stability under PEC conditions, compared to the ECD or the CBD films deposited separately. The electrodes combine the advantages of both ECD-copper selenide electrodes (in terms of good adherence to FTO surface and high surface uniformity) and CBD-copper selenide electrodes (suitable film thickness). Effect of annealing temperature, on the ECD/CBD film electrode composition and efficiency, is discussed.The results of this work are partly based on K. Murtada M.Sc. Thesis, under direct supervision of H.S. Hilal. Other experimental measurements and calculations, including dark current experiments, film thickness measurement, electrical conductivity, SEM analysis, XRD &AFM analysis revisions were performed by A. Zyoud after the thesis completion. Additional film electrode stability experiments under PEC conditions, were also performed by A. Zyoud after the Thesis completion. SEM micrographs and EDX spectra were measured by T.W. Kim and H-J.C. at the KIER, Korea. The XRD patterns were measured by D-H. Park and H. Kwon at PUK. M.H.S. Helal and H. Bsharat contributed with literature search, discussions and modeling. M. Faroun measured AFM micrographs at Al-Quds University. H.S. Hilal acknowledges financial support from ANU, Islamic Development Bank, Al-Maqdisi Project and Union of Arab Universities. T.W. Kim and H-J. Choi acknowledge financial support from the framework of the Research and Development Program of the Korea Institute of Energy Research (B6-2523)

Enhancement of electromagnetically deposited pristine CdTe film electrode photoelectrochemical characteristics by annealing temperature and cooling rate

Photoelectrochemical (PEC) characteristics of CdTe film electrodes, known to have low conversion efficiency when used in their pristine form, can be significantly enhanced by carefully controlling their annealing temperature and cooling rate. Pristine CdTe films were electrodeposited onto FTO/Glass substrates which were used as anodes. To reach films with optimal characteristics, different applied preparation potentials were intentionally examined, namely 1.0, 1.1 and 1.2 V, vs. Ag/AgCl reference electrode (or 1.2, 1.3 and 1.4 V NHE, respectively) where the 1.1 V applied potential showed best PEC characteristics, and was thus followed unless otherwise stated. To study effect of annealing temperature, three temperatures (150, 200 and 250 ºC) were attempted to enhance PEC characteristics of the deposited films. Effect of cooling rate, on PEC performance of pre-annealed films, was also studied using quenching and slow cooling. Films quenched from annealing at all temperatures showed lower PEC performance compared to non-annealed electrode. Film electrodes slowly cooled from 150 or 200 ºC show enhanced PEC performance compared to quenched or non-annealed films. Film slowly cooled from 250 ºC exhibited lower PEC performance than the quenched counterpart. Annealing at 250 ºC lowered PEC for both quenching and slow cooling. As a low band gap semiconductor film electrode, it is recommended to slowly cool CdTe from low annealing temperatures, and to quickly cool them from relatively higher annealing temperature. The annealing temperature and cooling rate effects on CdTe film PEC performance are attributed to their effects on other physical characteristics, namely crystallinity, morphology and chemical composition. The optimal conversion efficiency (6.9%) was observed for film deposited at 1.1 V applied potential when annealed at 200 ºC and slowly cooled to room temperature