| AVS 59th Annual International Symposium and Exhibition | |
| Thin Film | Thursday Sessions |
| Session TF-ThP |
| Session: | Thin Film Poster Session |
| Presenter: | M.A. Melendez-Lira, Cinvestav-IPN, Mexico |
| Authors: | K.E. Nieto-Zepeda, Cinvestav-IPN, Mexico E. Mota-Pineda, ESIME-IPN, Mexico M.A. Zapata-Torres, CICATA-Legaria, IPN, Mexico M.A. Melendez-Lira, Cinvestav-IPN, Mexico |
| Correspondent: | Click to Email |
The efficiency of photovoltaic structures based on the CdS/CdTe heterojunction is far from that predicted theoretically. Within the various problems that affect negatively the efficiency of this system is the lack of a methodology to get a controlled doping of the n-type window layer of CdS. The chemical bath deposition methodollogy generally produces uncontrolled n-type CdS films. This paper proposes the use of fluoride as an electron donor to substituting the atoms of S in CdS. With this objective we deposited CdS films using different molar compositions of thiourea doped with fluorine. The molar compositions used are between 0.025 and 0.25 M with variations of 0.025 M.The samples obtained were characterized by UV-Vis transmission spectroscopy, X-ray diffraction and the electric transport by I vs V measurements. Representative samples were characterized by using Atomic Force Microscopy, Scanning Electron Microscopy, Raman, photoluminescence and photoconductivity spectroscopies. The results are discussed considering the presence of defects associated with the molar concentration of thiourea. The crystallographic quality of the samples increases with fluorine doping. There is a growing trend in the band gap values with thiourea concentrations. Raman spectrosocopy results suggest that fluorine is substitutionally incorporated in sulphur sites and photoluminescence spectroscopy indicates that chemical bath deposited samples have a low density of radiative defects. IvsV curves indicated that transport is carried out through a percolation process. Our results indicated that the samples with the best characteristics are those fluorine doped grown with thiourea concentrations between 0.075 y 0.125 M showing that fluorine substitutionally replaces to sulphur and passivates interfacial states.
* This work has been partially supported by CONACyT-Mexico and Instituto de Ciencia y Tecnologia-DF