The development of devices with high efficiencies can only be attained by tandem structures which are important to the advancement of thin-film photoelectrochemical (PEC) and photovoltaic (PV) technologies. FSEC PV Materials Lab has developed a PEC cell using multiple bandgap tandem of thin film PV cells and a photocatalyst for hydrogen production by water splitting. CdS/CdTe solar cell, a promising candidate for low-cost, thin-film PV cell is used as one of the thin film solar cells in a PEC cell. This research work focuses on developing various back contacts with good transparency in the infrared region (~750 - 1150 nm) for a CdS/CdTe solar cell. CdS/CdTe solar cells were prepared with three different configurations, Glass/SnO2:F/CdS/CdTe/ZnTe:Cu/ITO/Ni-Al (series 1), Glass/SnO2:F/CdS/CdTe/Cu2Te/ITO/Ni-Al (series 2), Glass/SnO2:F/CdS/CdTe/Br-Me etching/Cu/ITO/Ni-Al (series 3). The back contact preparation process for a CdS/CdTe solar cell involves the deposition of a primary p-type back contact interface layer followed by the deposition of transparent and conducting ITO and a Ni-Al outer metallization layer. Back contact interface layers were initially optimized on glass substrates. A ZnTe:Cu layer for a series 1 cell was deposited using hot wall vacuum evaporation (HWVE). Cu2Te and Cu thin films for series 2 and series 3 cells were deposited by vacuum evaporation. HWVE technique produced highly stoichiometric ZnTe:Cu thin films with cubic phase having {111} texture orientation. All the back contact interface layers demonstrated better transparency in the infrared region on glass substrate. Formation of crystalline phase and texture orientation were studied using X-ray diffraction (XRD). The composition was analyzed by electron probe microanalysis (EPMA). Transparency measurements were carried out by optical transmission spectroscopy. Thickness measurements were carried out using a DEKTAK surface profile measuring system. Finally, completed solar cells for all the series were characterized for current-voltage (I-V) measurements using the I-V measurement setup developed at the FSEC PV Materials Lab. The PV parameters for the best series 1 cell measured at an irradiance of 1000 W/m2 were: open circuit voltage, Voc = 630 mV, short circuit current, Isc = 7.68 mA/ cm2, fill factor, FF = 37.91 %, efficiency, ç = 3.06 %. The PV parameters for the best series 2 cell measured were: Voc = 690 mV, Isc = 8.7 mA/ cm2, FF = 45.19 %, ç = 4.8 %. The PV parameters for the best series 3 cell measured were: Voc = 550 mV, Isc = 9.70 mA/ cm2, FF = 42.25 %, ç = 5.63 %. The loss in efficiency was attributed to the possible formation of a non-ohmic contact at the interface of CdTe and back contact interface layer. Decrease in the fill factor was attributed to high series resistance in the device.
| Identifer | oai:union.ndltd.org:ucf.edu/oai:stars.library.ucf.edu:etd-1427 |
| Date | 01 January 2005 |
| Creators | Avachat, Upendra Sureshchandra |
| Publisher | STARS |
| Source Sets | University of Central Florida |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | Electronic Theses and Dissertations |
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