The heterojunction ITO/CdS/Chl a/Ag (Chl a = chlorophyll a) solar cells have been prepared by sequential electrodeposition of CdS and Chl a onto conductive indium-tin oxide (ITO) electrode followed by vacuum deposition of Ag, and their photovoltaic studies have been carried out. The dark J-V and photovoltaic characteristics, especially the action spectra, suggest the presence of a barrier at CdS/Chl a interface. Various photovoltaic parameters of the cells obtained for the incident light power of 20 μW/cm2 at 740 nm, the maximum of Chl a absorption in red region, are as follows: JSC ≃ 150-200 nA/cm2, VOC ≈ 0.35-0.40 V, ff = 0.26, and η (%) = 0.17. The measurements performed at three wavelengths, namely, 740, 680, and 560 nm, indicate that the cells (illuminated through CdS electrode) perform better for weakly absorbed light at 560 nm. The results further show that the use of CdS instead of Al as rectifying electrode has definitely led to an improvement in the performance of CdS/Chl a over Al/Chl a cells in terms of the decreased internal resistances, decreased dark current and voltage, increased fill factors, and increased power conversion efficiencies. This has been attributed to the elimination of insulating layer of Al2O3 existing at Al/Chl a interface.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry