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Item Effect of temperature on photosensitivity of electrodeposited n-Cu2O/p-CuxS thin film junctions(Faculty of Science, University of Kelaniya, Sri Lanka, 2016) Madusanka, H.D.P.; Kalubowila, K.D.R.N.; Jayathilaka, K.M.D.C.; Jayanetti, J.K.D.S.The purpose of this study was the construction of a standalone microcontroller based ambient light sensing device to interface an ambient light sensor with a temperature correction and to study the effects of temperature on photosensitivity of electrodeposited Cu2O based thin film p-n junction diodes. Environmentally friendly, low cost, nontoxic cuprous oxides have highly acceptable electrical and optical properties. It has a direct energy gap of about 2 eV at room temperature and has a good absorption coefficient. Cuprous oxide has a good mobility for the majority carriers and a diffusion length of the minority carriers is several micrometers. In this study, an electrolytic solution of 0.1M sodium acetate and 0.01M cupric acetate was used to fabricate Cu2O thin films on top of Ti substrates using electrodeposition. Electrodeposition was carried out potentiostatically at a potential of -200 mV with respect to the saturated calomel electrode. A Na2S solution was used to make the n- Cu2O/p-CuxS junction. In order to increase the photocurrent from the fabricated n- Cu2O/p-CuxS junction, the sulphided Cu2O sample was exposed to ammonium sulphide gas. Then the photocurrent of the n-Cu2O/p-CuxS thin film junction was measured by a constructed microcontroller based light sensing device simultaneously monitoring the intensity of light with a luminance meter HS1010. An important observation made in this study was that the photocurrent of the electrodeposited Cu2O/CuxS thin film junctions depended greatly on the variation of temperature during exposure to light. Thus the junction photocurrent was studied by exposing the junctions to light while monitoring the variation in the photocurrent with the temperature using a DS18B20 temperature sensor. The resulting data were plotted using MATLAB software and it was found that the photocurrent of the thin film p-n junction displayed a variation that was very much linear at low intensities of light. The measured output currents obtained from the p-n junctions and the output values obtained from the temperature sensor were used to display the intensity of light with the temperature correction using an electronic circuit.Item Electrodeposited Cu2O homojunction solar cells: Fabrication of a cell of high short circuit photocurrent(Elsevier, 2016) Wijesundera, R.P.; Gunawardhana, L.K.A.D.D.S.; Siripala, W.A Cu2O homojunction solar cell was fabricated using a consecutive electrodeposition method of deposition of an n-Cu2O film followed by a p-Cu2O film, in two different acetate baths. Both n-type and p-type film growth conditions were optimized separately to yield high photocurrents in a photoelctrochemical (PEC) cell. Further, the resulted bi-layer films were investigated in the PEC for the verification of the formation of the p-n homojunction. In addition, p-Cu2O film surfaces of the bi-layers were sulphided using Na2S and (NH4)2S in order to improve the photoresponse of the homojunction before depositing a Au film for the solar cell device. The structural, morphological and optoelectronic properties of the Cu2O films were investigated using X-ray diffraction (XRD), scanning electron micrographs (SEMs), dark and light current–voltage (I-V) and spectral response measurements and observed that the films are of good quality. Incident photon to current efficiency (IPCE) and I-V characteristics of the solar cell device demonstrated that the Cu2O homojunction can produce a high short circuit current density Jsc. However, the overall conversion efficiency of the device is low due to poor fill factor and Voc. The solar cell characteristics of the structure Ti/n-Cu2O/p-Cu2O/Au were Voc=287.0±0.1 mV, Jsc=12.4±0. 1 mA/cm2, FF=25±2% and η=0.89±0.02%, under AM 1.5 illumination. The record high Jsc value of the device demonstrates the prospect being improved the efficiency of Cu2O homojunction solar cells by optimizing deposition, pretreatment and post treatment processes.Item Spectral responses of electrodeposited cuprous oxide thin film electrodes(Journal of the National Science Council of Sri Lanka, 1995) Siripala WPhotoresponse of the electrodeposited cuprous oxide thin film electrodes were investigated in a photoelectrochemical cell. Spectral response measurements reveal that a Schottky-type junction is formed at the junction between the substrate and cuprous oxide resulting in n-type and p-type photosignals in a photoelectrochemical cell. The electrodeposited cuprous oxide is an n-type semiconductor.