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Liyanage D.,University of Shizuoka | Bandara H.M.N.,University of Peradeniya | Jayaweera V.,SPD Laboratory Inc. | Murakami K.,University of Shizuoka
Applied Physics Express | Year: 2013

Fluorine-doped tin oxide nanorod transparent thin films were fabricated with SnCl4·5H2O, NH4F, and ethylene glycol (EG) using an improved spray pyrolysis deposition technique. The fabricated nanorods showed a low resistance of 15.3Ω/sq and a good transparency of 70.8%. The nanorods have a higher surface area than the conventionally used thin films. © 2013 The Japan Society of Applied Physics.

Jayaweera P.V.V.,SPD Laboratory Inc. | Pitigala P.K.D.D.P.,Georgia State University | Shao J.F.,Georgia State University | Shao J.F.,Lanzhou University | And 6 more authors.
IEEE Transactions on Electron Devices | Year: 2010

A low-cost photoconductive dual-band detector based on a ZnO film sensitized with lead sulfide quantum dots (PbS-QDs) is reported. The UV response arises from the interband absorption of UV radiation by ZnO, and the IR response is due to the absorption in the PbS-QDs. The detector exhibits UV response from 200 to 400 nm with a peak responsivity of 4.0×105 V/W and detectivity D of 5.5× 1011 Jones at 370 nm at room temperature. The observed visiblenear IR response is from 500 to 1400 nm with a responsivity of 5.4×105 V/W and D of 7.3×1011 Jones at 700 nm operating at room temperature. By increasing the PbS-QD size, the IR response can extend up to 2.9 μm. © 2006 IEEE.

Jayaweera P.M.,University of Sri Jayewardenepura | Jayaweera P.V.V.,SPD Laboratory Inc. | Jayasundara U.L.,University of Sri Jayewardenepura | Jayaweera C.D.,University of Sri Jayewardenepura | And 2 more authors.
Transactions of the Institutions of Mining and Metallurgy, Section C: Mineral Processing and Extractive Metallurgy | Year: 2011

The rate of leaching of iron from ilmenite (FeTiO 3) in hydrochloric acid (HCl) solutions is greatly enhanced by the presence of ultraviolet (UV) light. The magnitude of the air purged UV light illuminated leaching rate is approximately twofold higher than the N 2 purged leaching rate under dark conditions. The enhanced rate is attributed to the photo dissociation of polymeric titanium oxy species via oxidising radicals OH and HO 2 formed through Fe 3+/Fe 2+/H 2O Fenton type reactions. Photo dissociation and consequent non-deposition of polymer species in the pores of ilmenite particles cause the chemical reaction between FeTiO 3 and HCl acid in stirred solutions to become the rate determining step. The addition of H 2O 2 to the reaction mixture, in the presence and absence of UV light, further enhances iron leaching rate, confirming the role of radical species. © 2011 Institute of Materials.

Kumara G.R.A.,SPD Laboratory Inc. | Kawasaki S.,SPD Laboratory Inc. | Jayaweera P.V.V.,SPD Laboratory Inc. | Premalal E.V.A.,University of Shizuoka | Kaneko S.,SPD Laboratory Inc.
Thin Solid Films | Year: 2012

Construction of dye-sensitized solar cell of large area using platinum sputtered titanium metal counter electrode is demonstrated. An impressive increase in the fill factor and consequently the efficiency compared to the conventional platinized conducting glass based counter electrodes result from very low sheet resistance of the titanium plate and a cell of active area 151 cm 2 with parallel silver collecting grids delivered an efficiency of 7.4%. The possibility of using this technique for commercial production of dye-sensitized solar cells was discussed giving details of fabrication procedure. © 2011 Elsevier B.V. All rights reserved.

Yadav P.,Pandit Deendayal Petroleum University | Pandey K.,Pandit Deendayal Petroleum University | Tripathi B.,Pandit Deendayal Petroleum University | Jayaweera P.V.V.,SPD Laboratory Inc. | And 2 more authors.
Solar Energy | Year: 2016

In the present article, the direct current and alternating current characterization techniques are employed to investigate the losses during interfacial charge transport in dye-sensitized solar cell (area: 3.78 cm2) having a power conversion efficiency of 4.32%. The analysis of current-voltage characteristics depicts that the loss in photocurrent density is about 1-1.5% at low forward bias, ~8% at knee voltage and ~79% at open circuit voltage. The electrochemical impedance spectroscopy measurement leads to the direct determination of recombination resistance, chemical capacitance, charge transport resistance and double layer capacitance. The current-voltage characteristics obtained from the impedance parameters allows separating the contributions of different resistive processes on the overall conversion efficiency. The experimental results along with the analytical model provide an insight into the electric power loss mechanism, which is useful for analyzing performance of other upcoming devices with a similar working mechanism like perovskite sensitized solar cells. © 2016 Elsevier Ltd.

Premalal E.V.A.,University of Shizuoka | Dematage N.,University of Shizuoka | Kaneko S.,SPD Laboratory Inc. | Konno A.,University of Shizuoka
Thin Solid Films | Year: 2012

Fluorine-doped tin oxide (FTO) thin films were prepared, at different substrate temperatures, using dilute precursor solutions of di(n-butyl)tin(iv) diacetate (0.1 M DBTDA) by varying the F - concentration in the solution. It is noticed that conductivity of FTO film is increasing by increasing the fluorine amount in the solution. Morphology of SEM image reveals that grain size and its distribution are totally affected by the substrate temperature in which conductivity is altered. Among these FTO films, the best film obtained gives an electronic conductivity of 31.85 × 10 2 Ω - 1 cm - 1, sheet resistance of 4.4 Ω/□ (ρ = 3.14 × 10 - 4 Ω cm) with over 80% average normal transmittance between the 400 and 800 nm wavelength range. The best FTO film consists of a large distribution of grain sizes from 50 nm to 400 nm range and the optimum conditions used are 0.1 M DBTDA, 0.3 M ammonium fluoride, in a mixture of propan-2-ol and water, at 470 °C substrate temperature. The large distribution of grain sizes can be easily obtained using low DBTDA concentration (~ 0.1 M or less) and moderate substrate temperature (470°C). © 2012 Elsevier B.V.

Premalal E.V.A.,University of Shizuoka | Dematage N.,University of Shizuoka | Kaneko S.,SPD Laboratory Inc | Konno A.,University of Shizuoka
Electrochemistry | Year: 2012

Fluorine-doped tin oxide (FTO) thin films were prepared, at different substrate temperatures, using dilute precursor solutions of di(n-butyl)tin(iv) diacetate (0.1 M DBTDA) by varying the F - concentration in the solution. Morphology of SEM image revels that grain size and its distribution are affected by the substrate temperature. At the lowest temperature (400°C) the grain size become the smallest and at the highest temperature grain size become larger while at moderate temperature it has a large distribution of grain sizes. XPS calculation reveals that fluorine doping will decrease when substrate temperature is increased. Carrier concentration measured from hall coefficient analysis is found to be varying with the amount of fluorine doping as well as with the surface area of the film. Mobility becomes the lowest for the lowest grained FTO and it is the highest for the largest grained FTO. The best film, has large distribution of grain sizes (50-400 nm), gives an electronic conductivity of 31.85 Χ 10 2Ω -1cm -1, sheet resistance of 4.4fi/square with over 80% transmittance (400-800 nm). Optimum conditions of the best FTO film were 0.1 M DBTDA, 0.3 M ammonium fluoride, in a mixture of propan-2-ol and water, at 470°C substrate temperature. Dye-sensitized solar cells were fabricated using both the FTO films thus prepared and with the commercial FTO film. The best efficiency of 6.48% was observed for the cell fabricated from the best FTO films prepared at 470°C whereas the cells fabricated from the commercial FTO shows 5.30% light-to-electricity conversion efficiency (Illumination-A.M 1.5, Cell active area-1 cm 2, MPN based electrolyte-I -/I 3 -). © The Electrochemical Society of Japan All rights reserved.

Jayaweera P.V.V.,SPD Laboratory Inc. | Kaneko S.,SPD Laboratory Inc.
Instrumentation Science and Technology | Year: 2012

An electrolyte filling machine, capable of filling liquid electrolyte (including viscous ionic liquid) into an enclosed cell with a single hole, has been developed. This system utilizes a vacuum-aided filling technique and has four major steps in the filling process, namely evacuation, discharging, filling, and returning extra electrolyte. The electrolyte is not open to ambient conditions throughout the filling process, and the return step minimizes the waste of electrolyte. This technique allows air bubble-free filling, better insertion of electrolyte into the mesoporous titanium oxide layer of dye-sensitized solar cells (DSC), and filling time is 40s with a nonvolatile liquid-based electrolyte. Large area DSC modules that are 15*15cm in size were tested using this machine, and conversion efficiency of 7.4% was obtained under the standard air mass (AM) 1.5 simulated sunlight. © 2012 Taylor and Francis Group, LLC.

Cojocaru L.,Tokyo University of Science | Uchida S.,University of Tokyo | Jayaweera P.V.V.,SPD Laboratory Inc. | Kaneko H.,SPD Laboratory Inc. | And 3 more authors.
Chemistry Letters | Year: 2015

For efficient hybrid solar cells based on organometal halide perovskites, the real origin of the IV hysteresis became a big issue and has been discussed widely. In this study, simulated IV curves of different equivalent circuit models were validated with experimental IV curves of a planar perovskite solar cell with the power conversion efficiency (PCE) of 18.0% and 8.8% on reverse scan (from open circuit to short circuit) and forward scan (from short circuit to open circuit), respectively. We found that an equivalent circuit model with a series of double diodes, capacitors, shunt resistances, and single series resistance produces simulated IV curves with large hysteresis matching with the experimentally observed curves. The electrical capacitances generated by defects due to the lattice mismatch at the TiO2/CH3NH3PbI3 and CH3NH3PbI3/spiro-OMeTAD interface are truly responsible for the hysteresis in perovskite solar cells. © 2015 The Chemical Society of Japan.

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