Dark Signals and Photovoltaic Properties of Al/Chlorophyll a/Ag Cells

✍ Scribed by Mabrouki, M. ;Oueriagli, A. ;Outzourhit, A. ;Ameziane, E.L. ;Hotchandani, S. ;LeBlanc, R.M.

• Publisher: John Wiley and Sons
• Year: 2002
• Tongue: English
• Weight: 133 KB
• Volume: 191
• Category: Article
• ISSN: 0031-8965
• DOI: 10.1002/1521-396x(200205)191:1<345::aid-pssa345>3.0.co;2-n

✦ Synopsis

The electrical characteristics of Al/chlorophyll a/Ag (Al/Chl a/Ag) structures, prepared by electrodeposition of chlorophyll a onto vacuum evaporated aluminum and followed by evaporation of silver (Ag) top electrode, are presented. It was found that these cells present a short-circuit current and an open-circuit voltage in the dark which both evolve with the aging time. An analysis of the I-V characteristics suggests that these dark signals are due to electrochemical reactions at the Al/Chl a interface and to thermally detrapped carriers in the Chl a film. Furthermore, the temperature dependence of the I-V characteristics of these cells revealed a change in the conduction mechanisms in the Chl a film around 15 C. This is further confirmed by studying the variations of the photocurrent with temperature. The conversion efficiency of these cells was found to be on the order of 0.1%. A comparison of the action spectra of the cells and the absorption spectra of the Chl a films suggested that the photogeneration of free carriers is governed by the ionization of the photogenerated excitons.