Characterization of CuxOy - ZnO:A1 P-N junction for solar cell applications

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Keheze, Fanuel Mugwang'a
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Semiconductors thin films have found applications in various optoelectronics devices. Of much interest is the application in solar cells. Consequently, this has led to a continuous search for new semiconductor materials for solar cell applications. Various elements and compourids have been used to fabricate thin film semiconductors for solar cell applications like Si, AI, GaAs, CuInSe2, CuO among others. In this work, Cu.O, and ZnO:Al thin films on plain glass substrates have been deposited as single thin films for property characterization by reactive DC Magnetron Sputtering and evaporation techniques using an Edward Auto 306 Magnetron Sputtering System respectively. A CuXOy-ZnO:Al p-n junction was fabricated by reactive DC magnetron sputtering and reactive thermal evaporation technique on a glass slide with silver as contacts. Transmittance and reflectance data in the range 300 nm-2500 nm were obtained using UV-VIS NIR Spectrophotometer Solid State 3700 DUV for all the thin films samples that were prepared. Transmittance values of above 70% for Copper Oxide and above 80 % for AlO were observed. The optical measurements were simulated using SCOUT 98 software to determine optical constants and optical bad gap of the thin films. Band gap values of 1.62 eV _ 2.54 eV are observed for Copper Oxide and 3.18 eV - 3.42 eV for AlO. The surface sheet resistivities at room temperature of 298 K were found to vary with the deposition parameters and film thickness. Urbach energy for AlO was found to increase with doping levels from 2.08 x 10-4 to 2.18x 10-4 and varied between 0.6 x 10-4 to 1.92 x 10-4 for Copper Oxide. Current-Voltage (I-V) characteristic of the fabricated pn junction was obtained using solar simulator. From the I-V characteristic the following parameters were determined; open circuit voltage Voc = 0.579 V and the short circuit current Isc = 1.12 mA/m2 resulting in 0.42 % solar cell efficiency.
Department of Physics, 99 p. The TK 2960 .K4 2011
Solar cells, Photovoltaic power Systems, Solar batteries