Browsing by Author "Gajanayake, G.K.U.P."

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    Effect of CdTe nucleation layer on the performance of CdS/CdTe thin film solar cells
    (J Mater Sci, 2023) Gajanayake, G.K.U.P.; Lakmal, A.A.I.; De Silva, D.S.M.; Dassanayake, B. S.
    In this study, an electrodeposited CdTe nucleation layer (ED-CdTe*) was introduced on a chemical bath deposited (CBD) CdS layer prior to close-spaced sublimation (CSS) of the CdTe absorber layer to improve the efficiency of the CdS/CdTe solar cell by reducing the recombination mechanism in the depletion region. The ED-CdTe* nucleation layer grown in 40 s produced the highest efficiency of 9.12% with an open-circuit voltage (VOC) of 640 mV, while the CBD-CdS/CSS-CdTe solar cell delivered 8.07% efficiency, with a VOC of 596 mV. The ideality factor and the reverse saturate current density of the CBD-CdS/ED-CdTe*/CSS-CdTe solar cell were 2.28 and 6.65 × 10–5 mA/cm2, respectively. After being treated with CdCl2, the efficiency of the device with the nucleation layer (40 s) was elevated to 15.6% with a VOC of 761 mV, and that of the device with no nucleation layer was raised up to 14.6% with a VOC of 737 mV. Further, the solar cell with optimal ED-CdTe* nucleation layer showed the highest spectral response within the 400–900 nm wavelength range. The SEM and AFM analysis verified the formation of an ultrathin ED-CdTe* nucleation layer that can catalyse the film formation of CdTe by the CSS method while reducing the interface incongruity between CdS and CdTe layers.
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    Effect of thermal annealing of CBD-CdS on the electrical properties of CBD-CdS/ED-CdTe solar cell
    (Faculty of Science, University of Kelaniya, Sri Lanka, 2020) Gajanayake, G.K.U.P.; De Silva, D.S.M.; Atapattu, H.Y.R.; Thivakarasarma, T.
    Chemical bath deposition, Electrodeposition, Thermal annealing, CdS/CdTe solar cell Thermal annealing is one of the key steps to enhance the optoelectronic properties of the CdS/CdTe solar cells. In this study, the effects of annealing temperature and annealing time of chemical bath deposited (CBD) CdS on the electrical properties of CBD-CdS/electrodeposited (ED) CdTe solar cells were investigated. CBD-CdS layers were prepared using pre-optimized deposition conditions (90 ℃, 55 min) on fluorine doped tin oxide (FTO) glass substrates utilizing a bath consisted of 0.033 mol/L Cd(CH3COO)2, 0.667 mol/L CS(NH2)2 as cadmium and sulfur precursors, respectively and therein, 1 mol/L CH3CO2NH4 and 0.735 mol/L NH4OH were used for pH adjustment. Thereafter, a set of CBD-CdS samples prepared was annealed at different temperatures (350, 375 and 400 ℃) by varying the annealing time (10, 20, 30, and 40 min). Consequently, CdTe thin films were electrodeposited on annealed CBD-CdS substrates using an ED-bath consisted of 1.0 mol/L CdSO4 and 1.0 mmol/L TeO2 at pH of 2.3, temperature of 65 ℃, and potential of -650 mV against a saturated calomel electrode. The prepared glass/FTO/CBDCdS/ED-CdTe samples were air annealed (400 ℃, 20 min) and Cu/Au back contacts were deposited using thermal evaporation technique. The electrical properties of the CBD-CdS samples were investigated by photo-electrochemical cell (PEC) study at the CBD-CdS/electrolyte junction. As per the PEC analysis, CBD-CdS sample annealed at 375 ℃, 30 min has shown the highest short circuit current density (Jsc) of 21.5 μA/cm2 , while the sample annealed at 400 ℃, 10 min shown the highest open circuit voltage (Voc) of 499 mV. The electrical properties of the CBD-CdS/ED-CdTe/Cu/Au devices were investigated under AM 1.5 light source and therein, CBD-CdS sample annealed at 375 ℃, 30 min scored the highest Jsc (14.12 mA/cm2 ) and the one annealed at 400 ℃, 10 min displayed the highest Voc (616 mV). Also, the device annealed at 375 ℃, 30 min showed the lowest series resistance (205 Ω) while the one annealed at 400 ℃, 10 min demonstrated the highest shunt resistance (1401 Ω). Accordingly, the 375 ℃, 30 min and 400 ℃, 10 min were found to be the effective conditions for annealing CBD-CdS that can result in materials with better electrical properties for CBDCdS/ED-CdTe/Cu/Au device fabrication.