Physics
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Item Cu2O Homojunction Solar Cells: Efficiency Enhancement with a High Short Circuit Current(2024) Thejasiri, S. A. A. B.; Jayathilaka, K. M. D. C.; Kafi, F. S. B.; Kumara, L. S. R.; Seo, O.; Yasuno, S.; Sakata, O.; Siripala, W.; Wijesundera, R. P.Cu2O homojunction solar cells were fabricated using potentiostatic electrodeposition technique. n-Cu2O thin films were grown in an acetate bath while p-Cu2O thin films were grown in a lactate bath. In the growth of n-Cu2O films, cupric acetate concentration, pH and temperature of the bath, deposition potential and duration (film thickness) and annealing temperature were investigated. In the growth of p-Cu2O on n-Cu2O, concentration of copper sulphate and lactic acid solutions, pH and temperature of the bath, deposition potential and duration were investigated. In addition, the procedure of sulfidation of p-Cu2O film surface using (NH4)2S vapor, before depositing Au front contact, was also optimized to enhance the photoactive performance. The structural, morphological and optoelectronic properties of the Cu2O films were investigated using scanning electron microscopy (SEMs), high energy X-ray diffraction (HEXRD), hard X-ray photoelectron spectroscopy (HAXPES), spectral response and current–voltage (J-V) measurements. The best Cu2O homojunction solar cell exhibited Voc = 460 mV, Jsc = 12.99 mA·cm−2, FF = 42% and η = 2.51%, under AM 1.5 illumination. Efficiency enhancement with the record high Jsc value for the Cu2O homojunction solar cell has mainly been due to the optimization of pH of the n-Cu2O deposition bath and lactic acid concentration of the p-Cu2O deposition bath.Item Fabrication of inverted organic solar cells on stainless steel substrate with electrodeposited and spin coated ZnO buffer layers(Journal of Polymer Engineering, 2022) Namawardana, D. G. K. K.; Wanigasekara, R. M. G.; Wanninayake, W. T. M. A. P. K.; Jayathilaka, K. M. D. C.; Wijesundera, R. P.; Siripala, W.; Malik, M. I.Polymer based organic solar cells (OSCs) are of tremendous interest as suitable candidates for producing clean and renewable energy in recent years. In this study, inverted OSCs on stainless steel (SS) substrate with zinc oxide (ZnO) as the electron selective transport layer (ESTL), are investigated, occupying bulk heterojunction blend of regioregular poly(3-hexylthiophene) (P3HT) and phenyl- C61-butyric acid methyl ester (PCBM) as the active material and poly-(4,3-ethylene dioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) as the hole transport layer (HTL). The device structure is SS/ZnO/P3HT:PCBM/PEDOT:PSS/Au. ZnO films are prepared by spin coating and electrodeposition techniques, followed by annealing under ambient conditions. The insertion of ZnO layer between the SS substrate and active layer has improved short-circuit current ( Jsc), open-circuit voltage (Voc), fill factor (FF), and power conversion efficiency (PCE) compared to those of the reference cell without ZnO layer, achieving the highest efficiency of 0.66% for the device with spin coated ZnO from sol–gel technique. This enhancement can be attributed to the effective electron extraction and the increased crystallinity of ZnO after annealing treatments at higher temperatures as further confirmed by X-ray diffraction (XRD) and scanning electron microscope (SEM) analyses.Item Effect of pre-surface treatments on p-Cu2O/Au Schottky junctions(Journal of the National Science Foundation of Sri Lanka,, 2021) Kafi, F.S.B.; Jayathilaka, K.M.D.C.; Wijesundera, R.P.; Siripala, W.Cuprous oxide (Cu2O) is a suitable semiconducting material in fabrication for low-cost, eco-friendly semiconductor junction devices. Besides the parameterization of the growth conditions of Cu2O, formation of metal contacts impact the overall performance of these type of devices. The existence of unavoidable dangling bonds and/or dislocated surface atoms could lead to form imperfect contacts with metals, for example in Cu2O/Au junction devices. Nevertheless, modification of the Cu2O thin film surfaces prior to make contacts with Au has shown the capability to alter the junction properties. Here we report that, the application of surface treatments; annealing and/or sulphidation on specifically the electrodeposited p-Cu2O thin film surfaces, where p-Cu2O thin films were grown in low cupric ion concentrated acetate bath, has influenced the interfacial properties of particular p-Cu2O/Au Schottky junctions compared to the untreated p-Cu2O/Au Schottky junction. This has been well-established by the results of SEM and C-V characterizations of p-Cu2O/Au Schottky junctions. The subsequent annealing and sulphidation of p-Cu2O thin film surfaces have lowered the built-in potential value by 121 mV compared to the untreated Schottky junction. This result reveals the possibility of employing surface treatments on electrodeposited Cu2O thin films in fabrication of high efficient Cu2O based junction devices.Item A Comparative Study: Sequential and Single-Step-Electrodeposited CZTS Thin Films(Physica Status Solidi, 2022) Fernando, W. T. R. S.; Jayathilaka, K. M. D. C.; Wijesundera, R. P.; Siripala, W.CZTS (Cu2ZnSnS4) is a relatively new and promising semiconductor material suitable for photovoltaic applications due to its favorable optoelectronic properties. Of the many techniques available for growing these films, a comparative study on sequential and single-step electrodeposition methods to grow CZTS films is carried out in this investigation to explore the possibility of improving the quality of the films using the inexpensive electrodeposition technique. Mainly in both methods, potentiostatic electrodeposition technique is adopted for growing CZTS thin films. In both methods, growth conditions of the CZTS films are optimized after measuring the photoresponses in a photoelectrochemical (PEC) cell of the films that resulted at the end of each deposition step. The observed structural and optoelectronic properties of the films reveal that, in general, structurally good and photoactive CZTS films can be prepared using both methods. Moreover, photoresponse and Mott–Schottky measurements on CZTS films in a PEC reveal that CZTS films prepared using the single-step electrodeposition have better photoactive properties and improved doping densities. This important finding shows that when developing CZTS-based solar cells using the inexpensive electrodeposition technique, single-step electrodeposition is more advantageous.Item Fabrication Of Cuprous Oxide Homojunction Solar Cell By Varying The Lactic Acid Ion Concentration Of Thin Film p-Cu2O Deposition Bath.(ECS Transactions, 2022) Thejasiri, A.; Kafi, F. S. B.; Wijesundera, R.; Siripala, W.In this stud y, we have investigated the possibility of improving the Voe, FF and 1J values of Cu20 solar cells while preserving the resulted high Jsc values. Here we report that controlling the growth of p-Cu20 by varying the lactic acid ion concentration of thin film p-Cu20 deposition bath has improved the performance of Cu20 homo junction solar cell while preserving high J sc value. The fabricated surface treated thin film p-n homojunction solar cell has resulted Jsc = 12.95 mA cm-2, Voe = 445 mV, FF = 39.5% and 1J = 2.28%. The efficiency reported here is very significant in respect of Cu20 homojunction solar cells because it clearly demonstrates the possibility of adapting the low cost Cu20 material and fabrication methods in achieving a commercially viable solar cell.Item Effect of pre-surface treatments on p-Cu2O/Au Schottky junctions(Journal of the National Science Foundation of Sri Lanka, 2021) Kafi, F.S.B.; Jayathilaka, K.M.D.C.; Wijesundera, R.P.; Siripala, W.Cuprous oxide (Cu2O) is a suitable semiconducting material in fabrication for low-cost, eco-friendly semiconductor junction devices. Besides the parameterization of the growth conditions of Cu2O, formation of metal contacts impact the overall performance of these type of devices. The existence of unavoidable dangling bonds and/or dislocated surface atoms could lead to form imperfect contacts with metals, for example in Cu2O/Au junction devices. Nevertheless, modification of the Cu2O thin film surfaces prior to make contacts with Au has shown the capability to alter the junction properties. Here we report that, the application of surface treatments; annealing and/or sulphidation on specifically the electrodeposited p-Cu2O thin film surfaces, where p-Cu2O thin films were grown in low cupric ion concentrated acetate bath, has influenced the interfacial properties of particular p-Cu2O/Au Schottky junctions compared to the untreated p-Cu2O/Au Schottky junction. This has been well-established by the results of SEM and C-V characterizations of p-Cu2O/Au Schottky junctions. The subsequent annealing and sulphidation of p-Cu2O thin film surfaces have lowered the built-in potential value by 121 mV compared to the untreated Schottky junction. This result reveals the possibility of employing surface treatments on electrodeposited Cu2O thin films in fabrication of high efficient Cu2O based junction devices.