Simple strategies to enhance stability and solar conversion efficiency of metal chalcogenide film electrodes, IAPE, Oxford, UK, March 14-15, 2019
Publication Type
Conference Paper
Authors

Simple Strategies to Enhance Stability and Solar Conversion Efficiency of Metal Chalcogenide Film Electrodes

 

Hikmat S. Hilal

SSERL, Chemistry, An-Najah National University
University Street
Nablus, Palestine
Telephone number, +970-599273460

[email protected]

 

Ahed Zyoud

SSERL, Chemistry, An-Najah National University
University Street
Nablus, Palestine
Telephone number, 00970-59953404

[email protected]

 

 

 

Due to environmental, cost saving and starting material reduction reasons, polycrystalline film electrodes are emerging as alternatives to conventional solid p-n junctions in solar energy conversion. With their ease of preparation, band gap suitability and low cost, metal chalcogenide (MX; M = Cd, Cu, and others; X = S, Se or Te) based film electrodes are widely studied.  Such films, involving nano-size particles, are commonly prepared by chemical bath deposition, electro-deposition or other simple methods, and then used as working electrodes in photo-electrochemical (PEC) processes. However, literature shows that such electrodes suffer low stability and low conversion efficiency (less than 1% in many cases) under PEC processes, which dictates more research on enhancement strategies. Higher efficiency values of about 10% have been reported. According to US Department of Energy, the maximum conversion efficiency for metal chalcogenide film electrodes in 2020 is expected to be about 15%.  In our efforts to enhance both stability and conversion efficiency values for metal chalcogenide film electrodes, we have followed two simple strategies. To enhance film particle characteristics, and to enhance charge transfer inside the film itself, we have used controlled annealing and cooling rate of film electrodes. The basic factor here is the band gap value. Metal chalcogenides have low to medium band gap values. Based on basic physical models, low temperature annealing could enhance film characteristics, while higher temperatures should be avoided. Moreover, slow cooling rate is favourable in some cases and unfavourable in other cases, depending on the film type and the annealing temperature used.  Such practices showed enhanced charge transfer and lowered resistance inside the film itself. To further enhance charge transfer across the solid/liquid junction in PEC processes, metal chalcogenide film electrodes were coated with electro-active materials embedded inside polymeric films. The electro-active materials behaved as charge transfer catalysts at the interface. The catalyst speeds up the hole transfer from the film to the solution redox couple. By this way, the photocurrent density was enhanced. Moreover, no hole accumulation in the space charge layer, of the film surface, occurred. The electrode surface stability to photo-corrosion was thus stabilized under PEC conditions.  By combining both strategies together, metal chalcogenide film electrode stability and efficiency have been remarkably enhanced in these laboratories. Unprecedented conversion efficiency values of ~18% have been observed here for metal chalcogenide films. The results show the value of the described techniques in future applied energy. Details of results and their discussions will be described in this presentation. Theoretical models will also be presented to explain how the modification methods affect both conversion efficiency and film stability.

 

Keywords

Metal chalcogenide film electrodes; Solar energy conversion

Conference
Conference Title
Innovative Applied Energy (IAPE' 19)
Conference Country
United Kingdom
Conference Date
March 14, 2019 - March 15, 2019
Conference Sponsor
Agriculture and Agri-Food Canada
Additional Info
Conference Website