| 1. |
- Jayathilaka, K. M. D. C., et al.
(författare)
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Annealing effects of the untreated and sulfur-treated electrodeposited n-type and p-type cuprous oxide thin films
- 2016
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Ingår i: Physica status solidi. B, Basic research. - : Wiley. - 0370-1972 .- 1521-3951. ; 253:4, s. 765-769
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Tidskriftsartikel (refereegranskat)abstract
- The n-type and p-type cuprous oxide thin films were electrodeposited potentiostatically in acetate and lactate baths, respectively. Sulfur treatment of n-type and p-type cuprous oxide surfaces were achieved using gaseous (NH4)(2)S. Sulfur-treated Cu2O films were annealed in air at 100, 150, 200, 250, 350, and 450 degrees C for unique times to obtain the best photocurrent. Unannealed and annealed samples of sulfur-treated and untreated cuprous oxide were then investigated using high-energy X-ray diffraction (HEXRD). The HEXRD measurements and the pair distribution function (PDF) analysis revealed that the sulfur treatment leads to the formation of crystalline CuS on Cu2O film surfaces. The present study also shows that the sulfur treatment causes minor structural changes in Cu2O samples due to the formation of CuS. It was observed that the sulfur-treated cuprous oxide samples retarded the formation of CuO at higher temperatures showing good thermal stability and enhancement of the photoactivity of the n-type and p-type cuprous oxides.
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| 2. |
- Jayathilaka, K. M. D. C., et al.
(författare)
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Ammonium Sulfide Surface Treatment of Electrodeposited p-Type Cuprous Oxide Thin Films
- 2014
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Ingår i: Electronic Materials Letters. - : Springer Science and Business Media LLC. - 1738-8090 .- 2093-6788. ; 10:2, s. 379-382
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Tidskriftsartikel (refereegranskat)abstract
- The effects of ammonium sulfide surface treatment on electrodeposited p-type polycrystalline cuprous oxide (Cu2O) thin films deposited on Ti substrates were studied. The structural and morphological properties of the films were investigated using scanning electron microscopy, x-ray diffraction, and energy-dispersive x-ray spectroscopy. The changes in the conductivities and photocurrents of the films after the ammonium sulfide treatment were determined Films that had undergone the ammonium sulfide treatment showed reduced resistivities, enhanced spectral photoresponses, and enhanced current-voltage characteristics. The results showed that ammonium sulfide treatment improved the peak output current of the p-type Cu2O films by about 400% compared with those of bare Cu2O films. This improvement is attributed to the passivation of defects in the films by sulfur, showing that sulfur passivation provides a good method for improving of Cu2O-based devices.
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| 3. |
- Jayathilaka, K. M. D. C., et al.
(författare)
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Effect of chlorine doping on electrodeposited cuprous oxide thin films on Ti substrates
- 2015
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Ingår i: Physica status solidi. B, Basic research. - : Wiley. - 0370-1972 .- 1521-3951. ; 252:6, s. 1300-1305
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Tidskriftsartikel (refereegranskat)abstract
- Highly photoactive Cl-doped Cu2O films were electrodeposited potentiostatically on Ti substrates. Optimum deposition potential was determined by Linear-Sweep Voltammetry measurements. The influence of chlorine doping on grain size, crystallite shape and orientation was examined using scanning electron microscopy and X-ray diffraction. X-ray photoelectron spectroscopy confirmed the presence of Cl due to doping. Mott-Schottky electrochemical impedance analysis showed the p-type conductivity for undoped Cu2O films and n-type conductivity for Cl-doped Cu2O films. Analysis also showed that the carrier concentration of Cu2O thin films varied with Cl concentration of the deposition bath. Spectral responses of the resulting films were investigated in a photo-electrochemical cell to optimize the CuCl2 concentration of the deposition bath to obtain highly photoactive films. Photocurrent measurements further confirmed that the conductivity of these Cl-doped Cu2O films was n-type while undoped films showed p-type conductivity at a bath pH 9.3. The resistivity of Cu2O films decreased with the Cl concentration and the resistivity obtained for the Cl-doped Cu2O films with the highest photoactivity was about 10(2)cm at 30 degrees C. The low resistance and high photoactivity of Cl-doped cuprous oxide thin films make them more suitable for solar cell and other applications.
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| 4. |
- Jayathilaka, K. M. D. C., et al.
(författare)
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Sulfidation of electrodeposited microcrystalline/nanocrystalline cuprous oxide thin films for solar energy applications
- 2012
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Ingår i: Semiconductor Science and Technology. - : IOP Publishing. - 0268-1242 .- 1361-6641. ; 27:12, s. 125019-
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Tidskriftsartikel (refereegranskat)abstract
- Grain size of polycrystalline semiconductor thin films in solar cells is optimized to enhance the efficiency of solar cells. This paper reports results on an investigation carried out on electrodeposited n-type cuprous oxide (Cu2O) thin films on Ti substrates with small crystallites and sulfidation of them to produce a thin-film solar cell. During electrodeposition of Cu2O films, pH of an aqueous acetate bath was optimized to obtain films of grain size of about 100 nm, that were then used as templates to grow thicker n-type nanocrystalline Cu2O films. XRD and SEM analysis revealed that the films were of single phase and the substrates were well covered by the films. A junction of Cu2O/CuxS was formed by partially sulfiding the Cu2O films using an aqueous sodium sulfide solution. It was observed that the photovoltaic properties of nano Cu2O/CuxS heterojunction structures are better than micro Cu2O/CuxS heterojunction solar cells. Resulting Ti/nano Cu2O/CuxS/Au solar cell structure produced an energy conversion efficiency of 0.54%, V-oc = 610 mV and J(sc) = 3.4 mA cm(-2), under AM 1.5 illumination. This is a significant improvement compared to the use of microcrystalline thin film Cu2O in the solar cell structure where the efficiency of the cell was limited to 0.11%. This improvement is attributed mainly to the increased film surface area associated with nanocrystalline Cu2O films.
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| 5. |
- Jayathilaka, K. M. D. C., et al.
(författare)
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Surface treatment of electrodeposited n-type Cu2O thin films for applications in Cu2O based devices
- 2014
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Ingår i: Physica Status Solidi. Rapid Research Letters. - : Wiley. - 1862-6254 .- 1862-6270. ; 8:6, s. 592-595
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Tidskriftsartikel (refereegranskat)abstract
- In this Letter, we report the effects of ammonium sulfide [(NH4)(2)S] surface treatment on electrical and optical characteristics of the electrodeposited n-type Cu2O thin films on Ti substrates. Films characterized structurally and morphologically before and after the surface treatment were compared using conductivity, spectral photoresponse and current-voltage (I-V) measurements. The ammonium sulfide surface treatment time showed an impact on optical and electrical characteristics of the films. Treated Cu2O films exhibited enhanced conductivity giving rise to a 50-fold increase in the photocurrent and improved I-V characteristics. It was found that the sulfur passivation resulted in a nearly ohmic behaviour for Au or Ni contacts made with n-type Cu2O whereas Ag or Cu contacts showed nearly Schottky behaviour. The results showed that ammonium sulfide treatments were very effective to passivate defects and improve the optical and electrical properties of polycrystalline n-type Cu2O thin films that may provide a solid platform for Cu2O based devices of enhanced quality. [GRAPHICS] .
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