Characterization Of SnSe-CdO:Sn P-N Junction For Solar Cell Applications

ABSTRACT

Energy crisis occasioned by a decline in the availability of fossil fuels and increasing carbon dioxide emissions that are causing global warming has enhanced interest in the development of clean and renewable sources of energy. Solar energy has a great potential of meeting a large fraction of energy needs using photovoltaics. While most PV 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 PV cells with high conversion efficiency. In this study, SnSe and CdO:Sn thin films were optimised for photovoltaic 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 Keithley 2400 Source Meter respectively. Transmittance of the SnSe thin films deposited had transmittance ranging between 19-50% while reflectance ranged between 10-50%. The band gap values of SnSe thin films obtained were in the range of 1.71-1.76eV. SnSe thin films showed decrease of resistivity from 181-120Ωcm with increase in film thickness from 112-148nm. The optical properties of CdO:Sn showed high transparency in the visible region which varied with Sn doping, this makes CdO:Sn an excellent candidate for optoelectronic applications as a window layer. CdO and CdO:Sn had a transmittance of 70-85% and 50-89% respectively within the visible range of the electromagnetic spectrum. Reflectance of doped and undoped CdO was between 19-28%. Band gap energy for undoped CdO was 2.43eV while that of tin doped CdO ranged between 3.19-3.29eV for tin doping of 1-7%. Resistivity of CdO and CdO:Sn ranged between 16-93Ωcm. The optimised thin films were used to fabricate SnSe-CdO:Sn P-N junction. The I-V characteristics obtained were; Isc=0.993mA, Voc=273mV, Imax=0.905mA, Vmax=207mV, FF=0.69 and η = 0.59%.