Characterization of SnSe-CdO: Sn PN Junction for Solar Cell Applications
Makori, N. E.
Njoroge, W. K.
Karimi, P. M.
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Solar energy has a great potential of meeting a large fraction of energy needs using photovoltaics. While most photovoltaic cells in use today are Silicon-based, cells of other semiconductor materials have been manufactured. Considerable research has been focused in search of thin-film photovoltaic cells with high conversion efficiency. In our early studies, we reported optimization of Tin Selenide (SnSe) and Tin doped Cadmium Oxide (CdO:Sn) thin films for solar cell applications. SnSe and CdO:Sn thin films were successfully deposited by thermal and reactive thermal evaporation respectively using Edward’s Auto 306 Magnetron Sputtering System. Their optical and electrical properties were studied using Solid Spec-3700 DUV Spectrophotometer and Four-Point-Probe respectively. Transmittance of SnSe thin films deposited had transmittance ranging 0.01% to 45% while the band gap values obtained were in the range of 1.71eV to 1.76eV. SnSe thin films showed decrease of resistivity from 181Ωcm to120Ωcm with increase in film thickness from 112nm to 148nm. The optical properties of CdO:Sn showed high transparency in the visible region which varied with Sn doping. CdO and CdO:Sn had a transmittance of 70% to 85% and 50% to 89% respectively within the visible range of the electromagnetic spectrum. Band gap energy for undoped CdO was 2.43eV while that of tin doped CdO was in the range of 3.19eV to 3.29eV for tin doping of 1% to 7%. Resistivity of CdO was 42Ωcm while that of tin doped CdO ranged between 16Ωcm to 93Ωcm. In this study, the optimized thin films were used to fabricate SnSe-CdO:Sn P-N junction. SnSe of film thickness 148nm and 3% Sn doped CdO were used in the fabrication of the junction whose parameters are; Isc = 0.993mA, Voc = 273mV, Imax = 0.905mA, Vmax = 207mV, FF = 0.69 and η = 0.59%.