Fabrication and Characterization of  Copper System Compound Semiconductor  Solar Cells

Motoyoshi, Ryosuke; Oku, Takeo; Suzuki, Atsushi; Kikuchi, Kenji; Kikuchi, Shiomi; Jeyadevan, Balachandran; Cuya, Jhon

doi:https://doi.org/10.1155/2010/562842

Advances in Materials Science and Engineering

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Research Article | Open Access

Volume 2010 | Article ID 562842 | https://doi.org/10.1155/2010/562842

Fabrication and Characterization of Copper System Compound Semiconductor Solar Cells

Ryosuke Motoyoshi,¹Takeo Oku,¹Atsushi Suzuki,¹Kenji Kikuchi,¹Shiomi Kikuchi,¹Balachandran Jeyadevan,¹and Jhon Cuya¹

Academic Editor: Meilin Liu

Received19 Mar 2010

Revised14 Jun 2010

Accepted12 Jul 2010

Published20 Sept 2010

Abstract

Copper system compound semiconductor solar cells were produced by a spin-coating method, and their cell performance and structures were investigated. Copper indium disulfide- (CIS-) based solar cells with titanium dioxide () were produced on F-doped (FTO). A device based on an FTO/CIS/ structure provided better cell performance compared to that based on FTO//CIS structure. Cupric oxide- (CuO-) and cuprous oxide- (-) based solar cells with fullerene () were also fabricated on FTO and indium tin oxide (ITO). The microstructure and cell performance of the CuO/ heterojunction and the : bulk heterojunction structure were investigated. The photovoltaic devices based on FTO/CuO/ and ITO/: structures provided short-circuit current density of 0.015 and 0.11 , and open-circuit voltage of 0.045 V and 0.17 V under an Air Mass 1.5 illumination, respectively. The microstructures of the active layers were examined by X-ray diffraction and transmission electron microscopy.

1. Introduction

Chalcopyrite semiconductors are expected as one of the alternative materials to silicon solar cells. The features of chalcopyrite semiconductors include high optical absorption efficiency, low light degradation, and high radiation resistance. Copper indium disulfide, CuInS₂ (CIS) is a well-known p-type chalcopyrite semiconductor. CIS is a suitable material for high-efficiency solar cells because its bandgap (1.5 eV) is close to the ideal energy gap, which is well matched with the solar spectrum. In addition, the band structure shows direct transition, which provides a high efficiency. The highest efficiency of 12% as the absorber layer has been obtained for the CIS solar cells by using the expensive vacuum evaporation technique [1]. Most of the efficient CIS-based solar cells have been prepared by using CdS as buffer layers.

Cd-free CIS-based solar cells with TiO₂ and In₂O₃ have been fabricated by an evaporation method [2–4] and reported to show efficiencies of 3~9.5% [3, 4]. Titanium dioxide (TiO₂) as an n-type semiconductor has also been used as electrode materials for dye-sensitized solar cells [5]. TiO₂ is also a safe and low-cost material for environmentally harmonized solar cells. A low-cost method is essential for the mass production of CIS-based solar cells, and spin coating is a more economical method compared with vacuum evaporation [6–8]. CIS thin films deposited by sol-gel spin-coating methods have also been investigated and reported [9, 10]. The resulting structure closely resembles that of polymeric bulk heterojunction cells (polymer/) fabricated using organic materials [11–13]. The bulk heterojunction structures contribute to increase the p-n heterojunction interface for photoelectric conversion region in the devices. The aim of the present work was to investigate whether the /CIS structure by penetration of CIS nanocrystals into the porous layer could function as a bulk heterojunction structure.

Oxide semiconductors are one of the alternatives to silicon solar cells. Features of oxide semiconductors are high optical absorption and low cost of raw materials. Copper oxides (CuO and ) are well-known p-type oxide semiconductors. CuO and are suitable materials for high-efficiency solar cells because those direct bandgaps (1.5 eV and 2.0 eV) are close to the ideal energy gap for solar cells, and are well matched with the solar spectrum. The highest efficiency of 2% has been obtained for solar cells by using a high-temperature annealing method and an expensive vacuum evaporation technique [14]. Heterojunction solar cells with and ZnO have been fabricated by electrodeposition and photochemical deposition methods [15–17], and an efficiency of 0.001% was reported [17]. However, p-n heterojunction interface area for photoelectric conversion is small. One of improvements is to increase the p-n heterojunction interface by blending of p-type and n-type semiconductors, which are called bulk heterojunction solar cells [6–8]. Although CuO is used as a hole transfer layer and a barrier layer for dye-sensitized solar cells [18, 19], few solar cells with CuO used as a p-type semiconductor active layer have been investigated. The advantage of CuO is a simple production method.

Fullerene is a good acceptor material for solar cells, and has been used as n-type semiconductor active layer for organic thin film solar cells [12, 20]. A low-cost method is essential for mass production of CuO-based solar cells, and spin coating is a more economical method compared to vacuum evaporation [6, 7]. CuO thin films deposited by sol-gel spin-coating methods have also been investigated and reported [21].

The purpose of the present work was to prepare copper-based semiconductor solar cells by using a spin-coating method, and to investigate the microstructures and photovoltaic properties for /CIS and CuO/C₆₀ and : structures. The solar cells were investigated by microstructure analysis, optical absorption, and electronic property measurements.

2. Experimental Procedures

2.1. Fabrication of Dioxide/Copper Indium Disulfide Solar Cells

Two types of solar cells with /CIS and CIS/ structures were fabricated as shown in Figures 1(a) and 1(b), respectively. and CIS layers were coated on precleaned F-doped (FTO) glass plates (Asahi Glass, 9.3 Ω/□) by using a spin-coating method. layers with a thickness of 10 m were prepared by squee-gee coating using a paste (0.6 g/mL) of fine powders (P25, Sigma Aldrich) in an acetylacetone/polyethylene glycol solution and were annealed at for 30 minutes in air [22]. Copper acetate monohydrate, (0.5 mol/L, Sigma Aldrich, 99.99%) and indium acetate, In (0.5 mol/L, Sigma Aldrich, 99.99%) were dissolved into 2-propanol/monoethanolamine with a ratio of 4 : 1 and 1-propanol/diethanolamine with a ratio of 4 : 1, respectively, and the two solutions were then mixed. The molar ratio of Cu:In was 1 : 1. Cu-In layers of CIS precursor substance were prepared by spin coating at 1000 rpm using a mixed Cu-In solution. The Cu-In films were annealed at under an atmosphere for 30 minutes. The films were sulfurated by dipping in sulfur solution (1.0 mol/L) in o-dichlorobenzene. After annealing at for 30 minutes. in a (95%)/ (5%) mixture gas, CIS layers with a thickness of 100 nm were formed from the Cu-In films.

(a)

(b)

(c)

(d)

2.2. Fabrication of Copper Oxide/Fullerene Solar Cells

CuO and layers were coated on precleaned FTO glass plates (Asahi Glass, 9.3 Ω/□) by using a spin-coating method. Copper acetate monohydrate, (0.5 mol/L, Sigma Aldrich, 99.99%) was dissolved into 2-propanol/monoethanolamine. Cu layers of CuO precursor substance were prepared by spin coating at 1000 rpm using the mixture Cu solution. After annealing at under air atmosphere for 3 hours, CuO layers with a thickness of 100 nm were formed from the Cu(II) films. layers with a thickness of 100 nm were prepared on a CuO layer by spin coating using a solution (16 mg/mL) with powders (Material Technologies Research, 99.98%) in o-dichlorobenzene, and were annealed at for 30 minutes in atmosphere.

nanoparticles were synthesized by reducing copper-amine complex with 1-heptanol in the presence of tetramethyl ammonium hydroxide. The details of the synthesis scheme were as follows: Copper acetate and oleylamine were introduced into 1-heptanol and heated under a nitrogen atmosphere at for one hour to remove the moisture in the system. Then, tetramethyl ammonium hydroxide (TMAOH) dissolved in 1-hepatanol (15) was introduced and the suspension was heated at for 2 hours. Next, the suspension was cooled to room temperature and nanoparticles were recovered by centrifuging. Finally, the nanoparticles were washed with methanol to remove excess oleylamine, and the nanoparticles (100 mg) were dispersed in toluene (10 mL). A thin layer of polyethylenedioxythiophene doped with polystyrene-sulfonic acid (PEDOT:PSS) (Sigma Aldrich) was spin-coated at 2000 rpm on precleaned indium tin oxide (ITO) glass plates (Geomatec Co., Ltd., 10 Ω/□). After annealing at for 10 minutes in atmosphere, semiconductor layers were prepared on a PEDOT layer by spin coating using a mixed solution of a toluene with nanoparticle and a solution (16 mg/mL) with powders (Material Technologies Research, 99.98%) in o-dichlorobenzene. The thickness of the bulk heterojunction structure was approximately 150 nm. The : layers were annealed at for 30 minutes in atmosphere.

For all the present copper system compound semiconductor solar cells, aluminum (Al) metal contacts with a thickness of 100 nm were deposited as top electrodes, and annealed at for 20 minutes in atmosphere. Schematic illustrations of the present solar cells are shown in Figure 1.

2.3. Measurements of Solar Cells

The current density-voltage () characteristics (Hokuto Denko Corp., HSV-100) of the solar cells were measured both in the dark and under illumination at 100 mW/ by using an AM 1.5 solar simulator (San-ei Electric, XES-301S) in atmosphere. The solar cells were illuminated through the side of the FTO and ITO substrates, and the illuminated area was 0.16 Optical absorption of the solar cells was investigated by means of UV-visible spectroscopy (Hitachi, Ltd., U-4100). The microstructures of the CIS, copper oxides, and thin films were investigated by X-ray diffractometer (XRD, PHILIPS X’Pert-MPD System) with radiation operating at 40 kV and 40 mA, scanning electron microscopy (SEM, Hitachi, Ltd., S-3200N), energy dispersive X-ray analysis (EDX, EMAX-5770W), and transmission electron microscopy (TEM) operating at 200 kV (Hitachi, Ltd., H-8100).

3. Results and Discussion

3.1. CIS/ Solar Cells

The characteristics of the /CIS and CIS/ structures in the dark and under illumination were measured. The photocurrent was observed under illumination and both structures showed characteristic curves with open-circuit voltage and short-circuit current. The measured parameters of these solar cells are summarized in Table 1. A solar cell with the CIS/TiO₂ structure provided power conversion efficiency of %, fill factor (FF) of 0.25, short-circuit current density of mA/cm², and open-circuit voltage of V, which is better than those of the /CIS device.

Figure 2 shows the measured optical absorption of the solar cells. The /CIS structure shows high absorption at 444, 510, 606, and 738 nm, which correspond to 2.8, 2.4, 2.0, and 1.7 eV, respectively. The CIS/ structure also shows high optical absorption at 420, 488, 590, and 710 nm, which correspond to 2.6, 2.5, 2.1, and 1.7 eV, respectively. The absorption peaks at 444 nm and 420 nm for the /CIS and CIS/ structures were due to and the other peaks were due to CIS. As shown in Figure 2, the optical absorption between 400 nm and 800 nm for the /CIS solar cell is higher than that of CIS/ structure. The increase in film thickness of the CIS layer in the /CIS structure through the penetration of the CIS nanocrystals into the porous layer results in the increase in the optical absorption of solar cells in the /CIS structure.

Microstructures of the CIS thin film were investigated by XRD, as shown in Figure 3(a). Diffraction peaks corresponding to CIS and indium oxide were observed for the CIS thin film. The crystallite size was estimated using the Scherer equation: = 0.9 / cosθ, where and θ represent the wavelength of the X-ray source, the full width at half maximum (FWHM), and the Bragg angle, respectively [23]. From the FWHM of the 112 peak, the crystallite size of CIS was determined to be 13.1 nm. Elemental analysis of the CIS thin film was investigated by SEM and EDX. The atomic concentrations of the CIS thin film were copper (28.0%), indium (26.0%) and sulfur (46.0%).

(a)

(b)

(c)

Preparation conditions of the /CIS structure were different from those of the CIS/ structure, and influence of different annealing temperatures of the layer was investigated. Figures 3(b) and 3(c) show X-ray diffraction patterns of the thin films on the glass substrates annealed at for 30 minutes in air, and for 30 minutes in atmosphere and annealed at for 30 minutes in air, respectively. The X-ray diffraction patterns indicate an anatase phase with a tetragonal system, and there was a slight amount of the rutile phase. The particle size of the anatase phase was estimated to be 26.1 nm from the Scherrer’s equation. No differences between Figures 3(b) and 3(c) were observed on the crystalline structures of the layer.

Figures 4(a) and 4(b) show a TEM image and an electron diffraction pattern of the /CIS composite film, respectively. The TEM image indicated nanocrystals in the CIS matrix. Debye-Scherrer rings, which indicate polycrystalline structures of and 112 reflection of the CIS crystal can be seen in Figure 4(b). Enlarged high-resolution electron microscopy (HREM) images of the and CIS in Figure 4(a) are shown in Figures 4(c) and 4(d), respectively, revealing the lattice fringes of the 101 of the and the 112 of the CIS crystals.

(a)

(b)

(c)

(d)

Figures 5(a) and 5(b) show the microstructures of FTO//CIS/Al and FTO/CIS//Al, respectively. As shown in Figure 5(a), the porous layer has a composite structure with CIS nanocrystals. Therefore, the p-n junction interface area, which is the photoelectron conversion region in the /CIS solar cells, becomes larger compared to the ordinary heterojunction structure, leading to an increase in efficiency. As shown in Figure 2, the optical absorption between 400 nm and 800 nm for the /CIS solar cell is higher than that of CIS/ structure. The increase of the CIS layer thickness in the /CIS structure through the penetration of the CIS nanocrystals into the porous layer would result in the increase of the optical absorption of /CIS solar cells. Charge separation for the /CIS solar cell would be higher from high optical absorption. However, the carrier recombination of electrons and holes would occur at the FTO/ interface for the /CIS structure, and the energy conversion efficiency would not be improved by an increase of the p-n heterojunction interface in the present work.

(a)

(b)

(c)

(d)

Energy level diagrams of /CIS and CIS/ solar cells are summarized as shown in Figures 5(c) and 5(d), respectively. Previously reported values were used for the energy levels [24, 25]. It has been reported that is nearly proportional to the bandgap of the semiconductors [26].

Compared to a Si semiconductor with an indirect transition band structure, the CIS with a direct transition band structure is the more suitable for the optical absorption property. In addition, the ultrathin film of the CIS layers could provide an efficient charge injection because of the high optical absorption. Although (CIGS) has been mainly used as a p-type inorganic semiconductor for solar cells [27], CIS was applied instead of CIGS in the present work. Advantages of the present CIS are the low-cost reagent and the simple fabrication process. and CIS have stable properties against sunlight, and prevent photodeterioration for the solar cells. CIS-based solar cells are expected to provide a long life time.

CIS-based solar cells prepared by a spin-coating method without vacuum evaporation were investigated in the present work. The low conversion efficiency of the present solar cells is due to presence of impure compounds in the active layer. The defects produced by inadequate crystals would cause carrier recombination. Optimization of the CIS microstructures can increase the efficiency of solar cells. There could be carrier recombination of electrons and holes at the rear surface of the n-type electrode (FTO). Solar cells with a buffer layer fabricated by addition of ultrathin or ZnO n-type semiconductor layers between FTO and have been reported [28, 29]. Energy conversion efficiency could be improved by addition of the buffer layers to inhibit carrier recombination at the contact surfaces.

3.2. CuO/ Solar Cells

characteristics of the CuO/ structures in the dark and under illumination were investigated. The photocurrent was observed under illumination, and the CuO/ structure showed characteristic curves with short-circuit current and open-circuit voltage. Measured parameters of these solar cells are summarized in Table 1. A solar cell with a CuO/ structure provided of FF of 0.25, of 0.015 mA and of 0.045 V.

Figure 6 shows the measured optical absorption of the CuO/ solar cell. The absorption peaks around 350 nm in the CuO/ structure were due to CuO, and absorption peaks around 338 nm, 440 nm, and 606 nm correspond to

Figure 7 shows an X-ray diffraction pattern of the CuO thin films on glass substrates annealed at for 3 hours in air. Diffraction peaks corresponding to CuO were observed for the CuO thin film, which consisted of a tenorite phase with monoclinic system (space group of C2/c and lattice parameters of nm, nm, nm, and ). The crystallite size was estimated using Scherrer’s equation. From the FWHM of the peak, the crystallite size of CuO was determined to be 16.0 nm. Figures 8(a) and 8(b) show a TEM image and an electron diffraction pattern of the CuO thin film annealed at respectively. The TEM image indicated CuO nanocrystals with sizes of 1020 nm, which agree well with XRD results. Debye-Scherrer rings in Figure 8(b) indicate polycrystalline structures of CuO.

(a)

(b)

Energy level diagram of CuO/ solar cells is summarized as shown in Figure 9. Previously reported values were used for the energy levels [20, 30, 31]. Compared to the Si semiconductor with an indirect transition band structure, CuO with a direct transition bandgap is more suitable for the optical absorption property. Although has been mainly used as a p-type oxide semiconductor for solar cells [14–17], CuO was applied instead of in the present work. The advantages of the present CuO are low-cost reagent and the simple fabrication process.

CuO-based solar cells prepared by a spin-coating method without vacuum evaporation were investigated in the present work. The low conversion efficiency of the present solar cells would be due to carrier recombination by the defects produced by inadequate crystalline, and presence of CuO compounds with heterogeneous grain size in the active layer. Formation of the high-quality CuO thin films could increase the efficiency of solar cells.

3.3. : Solar Cells

The CuO/ solar cell was a heterojunction structure. To increase the interfacial area of p-n junction, / bulk heterojunction solar cells were prepared. The characteristics of the : structure in the dark and under illumination were measured. The photocurrent was observed under illumination, and the : structure showed photovoltaic properties. The measured parameters of the solar cells are summarized in Table 1. A solar cell with a : structure provided of FF of 0.23, of 0.11 mA and of 0.17 V.

Figure 10 shows optical absorption of the : solar cells. An absorption peak around 324 nm for the : structure is due to , and the absorption peak around 362 nm and 476 nm corresponds to .

Microstructures of the : thin films were investigated by XRD, as shown in Figure 11. Diffraction peaks corresponding to and were observed for the : thin film, and they consisted of a cuprite phase with cubic system (space group of Pn3m and a lattice parameter of = 0.4250 nm), and a phase with cubic system (space group of Fm3m and a lattice parameter of = 1.4166 nm). The crystallite sizes of and were determined to be 7.2 nm and 25.7 nm, respectively.

Figures 12(a) and 12(b) show a TEM image and a selected area diffraction pattern of the : thin film annealed at respectively. The TEM image indicated aggregated nanocrystals with sizes of 1020 nm. Line broadening of the Debye-Scherrer rings in Figure 12(b) indicates nanocrystal structures of . peaks [32] were not observed in this pattern, which would be due to dispersion of crystals. Optimization of the nanocomposite structure with and would increase the efficiencies of the solar cells.

(a)

(b)

Energy level diagram of the : solar cell is summarized as shown in Figure 13. Previously reported values were used for the energy levels [11, 31, 33]. with a direct transition bandgap is more suitable for the optical absorption property compared to Si. Although ZnO has been mainly used as an n-type oxide semiconductor for solar cells [14–17], was applied instead of ZnO in the present work. Advantages of the present are a good acceptor for solar cells and the simple fabrication process.

Compared to previously reported -based heterojunction solar cells [14], copper oxide-based bulk heterojunction and heterojunction solar cells prepared by a spin-coating method without a vacuum system were investigated in the present work, as listed in Table 2. The present copper oxide-based bulk heterojunction and heterojunction solar cells have simple fabrication process and good cost performance.

The low conversion efficiency of the present solar cells would be due to aggregation of nanoparticle in the active layer, which would cause carrier recombination. Formation of the : thin films with homogeneous distribution of nanoparticles could increase the efficiency of solar cells.

4. Conclusions

Copper system compound semiconductor solar cells were produced and characterized. A device based on the CIS/ structure provided of FF of 0.25, of mA/ and of V, which showed better performance compared to that of a device based on the /CIS structure. The devices based on the CuO/ and : structures were fabricated by a spin-coating method which provided of % and FF of 0.25 and 0.23, of 0.015 mA and 0.11 mA and of 0.045 V and 0.17 V, respectively. X-ray diffraction analysis indicated the formation of CIS, CuO, and nanocrystal structures, respectively.

Energy level diagrams of CIS/ CuO/ and : solar cells were proposed. Separated holes could transfer from the valence band of the copper system compound semiconductors to the transparent conducting oxide electrodes, and separated electrons could transfer from the conduction band of the copper system compound semiconductors to the Al electrodes, respectively.

Formation of the high-quality in active layers with inorganic nanoparticles would improve the efficiencies of the solar cells. The bulk heterojunction structure with dispersed inorganic nanoparticles in present work was effective for the improvement of current density.

Acknowledgment

This paper is partly supported by Takahashi Industrial and Economic Research Foundation.

References

T. Ohashi, Y. Hashimoto, and K. Ito, “Solar cells with $Cu ({In}_{1 - x} {Ga}_{x}) S_{2}$ thin films prepared by sulfurization,” Solar Energy Materials and Solar Cells, vol. 67, no. 1-4, pp. 225–230, 2001.
View at: Publisher Site | Google Scholar
M. Nanu, J. Schoonman, and A. Goossens, “Solar-energy conversion in ${TiO}_{2}$ / ${CuInS}_{2}$ nanocomposites,” Advanced Functional Materials, vol. 15, no. 1, pp. 95–100, 2005.
View at: Publisher Site | Google Scholar
F. Lenzmann, M. Nanu, O. Kijatkina, and A. Belaidi, “Substantial improvement of the photovoltaic characteristics of ${TiO}_{2}$ / ${CuInS}_{2}$ interfaces by the use of recombination barrier coatings,” Thin Solid Films, vol. 451-452, pp. 639–643, 2004.
View at: Publisher Site | Google Scholar
T. T. John, M. Mathew, C. S. Kartha, K. P. Vijayakumar, T. Abe, and Y. Kashiwaba, “ ${CuInS}_{2}$ / ${In}_{2} S_{3}$ thin film solar cell using spray pyrolysis technique having 9.5% efficiency,” Solar Energy Materials and Solar Cells, vol. 89, no. 1, pp. 27–36, 2005.
View at: Publisher Site | Google Scholar
H.-J. Koo, Y. J. Kim, Y. H. Lee, W. I. Lee, K. Kim, and N.-G. Park, “Nano-embossed hollow spherical ${TiO}_{2}$ as bifunctional material for high-efficiency dye-sensitized solar cells,” Advanced Materials, vol. 20, no. 1, pp. 195–199, 2008.
View at: Publisher Site | Google Scholar
G. Yu and A. J. Heeger, “Charge separation and photovoltaic conversion in polymer composites with internal donor/acceptor heterojunctions,” Journal of Applied Physics, vol. 78, no. 7, pp. 4510–4515, 1995.
View at: Publisher Site | Google Scholar
F. Padinger, R. S. Rittberger, and N. S. Sariciftci, “Effects of postproduction treatment on plastic solar cells,” Advanced Functional Materials, vol. 13, no. 1, pp. 85–88, 2003.
View at: Publisher Site | Google Scholar
Y. Hayashi, I. Yamada, S. Takagi, A. Takasu, T. Soga, and T. Jimbo, “Influence of structure and $C_{60}$ composition on properties of blends and bilayers of organic donor-acceptor polymer/ $C_{60}$ photovoltaic devices,” Japanese Journal of Applied Physics, vol. 44, no. 3, pp. 1296–1300, 2005.
View at: Publisher Site | Google Scholar
S.-Y. Lee and B.-O. Park, “ ${CuInS}_{2}$ thin films deposited by sol-gel spin-coating method,” Thin Solid Films, vol. 516, no. 12, pp. 3862–3864, 2008.
View at: Publisher Site | Google Scholar
T. Todorov, E. Cordoncillo, J. F. Sánchez-Royo, J. Carda, and P. Escribano, “ ${CuInS}_{2}$ films for photovoltaic applications deposited by a low-cost method,” Chemistry of Materials, vol. 18, no. 13, pp. 3145–3150, 2006.
View at: Publisher Site | Google Scholar
T. Oku, S. Nagaoka, A. Suzuki et al., “Formation and characterization of polymer/fullerene bulk heterojunction solar cells,” Journal of Physics and Chemistry of Solids, vol. 69, no. 5-6, pp. 1276–1279, 2008.
View at: Publisher Site | Google Scholar
T. Oku, T. Noma, A. Suzuki, K. Kikuchi, and S. Kikuchi, “Fabrication and characterization of fullerene/porphyrin bulk heterojunction solar cells,” Journal of Physics and Chemistry of Solids, vol. 71, no. 4, pp. 551–555, 2010.
View at: Publisher Site | Google Scholar
R. Motoyoshi, A. Suzuki, K. Kikuchi, and T. Oku, “Formation and characterization of copper tetrakis (4-cumylphenoxy) phthalocyanine:perylene solar cells,” Synthetic Metals, vol. 159, no. 13, pp. 1345–1348, 2009.
View at: Publisher Site | Google Scholar
A. Mittiga, E. Salza, F. Sarto, M. Tucci, and R. Vasanthi, “Heterojunction solar cell with 2% efficiency based on a ${Cu}_{2} O$ substrate,” Applied Physics Letters, vol. 88, no. 16, Article ID 163502, 2006.
View at: Publisher Site | Google Scholar
M. Izaki, T. Shinagawa, K.-T. Mizuno, Y. Ida, M. Inaba, and A. Tasaka, “Electrochemically constructed p- ${Cu}_{2} O$ /n-ZnO heterojunction diode for photovoltaic device,” Journal of Physics D, vol. 40, no. 11, article no. 010, pp. 3326–3329, 2007.
View at: Publisher Site | Google Scholar
S. S. Jeong, A. Mittiga, E. Salza, A. Masci, and S. Passerini, “Electrodeposited ZnO/ ${Cu}_{2} O$ heterojunction solar cells,” Electrochimica Acta, vol. 53, no. 5, pp. 2226–2231, 2008.
View at: Publisher Site | Google Scholar
M. Izaki, K.-T. Mizuno, T. Shinagawa, M. Inaba, and A. Tasaka, “Photochemical construction of photovoltaic device composed of p-copper(I) oxide and n-zinc oxide,” Journal of the Electrochemical Society, vol. 153, no. 9, pp. C668–C672, 2006.
View at: Publisher Site | Google Scholar
S. Anandan, X. Wen, and S. Yang, “Room temperature growth of CuO nanorod arrays on copper and their application as a cathode in dye-sensitized solar cells,” Materials Chemistry and Physics, vol. 93, no. 1, pp. 35–40, 2005.
View at: Publisher Site | Google Scholar
P. Raksa, S. Nilphai, A. Gardchareon, and S. Choopun, “Copper oxide thin film and nanowire as a barrier in ZnO dye-sensitized solar cells,” Thin Solid Films, vol. 517, no. 17, pp. 4741–4744, 2009.
View at: Publisher Site | Google Scholar
A. Takeda, T. Oku, A. Suzuki, K. Kikuchi, and S. Kikuchi, “Fabrication and characterization of inorganic-organic hybrid solar cells based on ${CuInS}_{2}$ ,” Nippon Seramikkusu Kyokai Gakujutsu Ronbunshi/Journal of the Ceramic Society of Japan, vol. 117, no. 1369, pp. 967–969, 2009.
View at: Google Scholar
L. Armelao, D. Barreca, M. Bertapelle, G. Bottaro, C. Sada, and E. Tondello, “A sol-gel approach to nanophasic copper oxide thin films,” Thin Solid Films, vol. 442, no. 1-2, pp. 48–52, 2003.
View at: Publisher Site | Google Scholar
L. N. Lewis, J. L. Spivack, S. Gasaway et al., “A novel UV-mediated low-temperature sintering of ${TiO}_{2}$ for dye-sensitized solar cells,” Solar Energy Materials and Solar Cells, vol. 90, no. 7-8, pp. 1041–1051, 2006.
View at: Publisher Site | Google Scholar
N.-G. Park, M. G. Kang, K. S. Ryu, K. M. Kim, and S. H. Chang, “Photovoltaic characteristics of dye-sensitized surface-modified nanocrystalline ${SnO}_{2}$ solar cells,” Journal of Photochemistry and Photobiology A, vol. 161, no. 2-3, pp. 105–110, 2004.
View at: Publisher Site | Google Scholar
E. Arici, N. S. Sariciftci, and D. Meissner, “Hybrid solar cells based on nanoparticles of ${CuInS}_{2}$ in organic matrices,” Advanced Functional Materials, vol. 13, no. 2, pp. 165–170, 2003.
View at: Publisher Site | Google Scholar
Q. Qiao and J. T. McLeskey Jr., “Water-soluble polythiophenenanocrystalline ${TiO}_{2}$ solar cells,” Applied Physics Letters, vol. 86, no. 15, Article ID 153501, 3 pages, 2005.
View at: Publisher Site | Google Scholar
M. A. Green, K. Emery, D. L. King, Y. Hishikawa, and W. Warta, “Solar cell efficiency tables (version 28),” Progress in Photovoltaics: Research and Applications, vol. 14, no. 5, pp. 455–461, 2006.
View at: Publisher Site | Google Scholar
M. A. Contreras, K. Ramanathan, J. AbuShama et al., “Diode characteristics in state-of-the-art $ZnO / CdS / Cu ({In}_{1 - x} {Ga}_{x}) {Se}_{2}$ solar cells,” Progress in Photovoltaics: Research and Applications, vol. 13, no. 3, pp. 209–216, 2005.
View at: Publisher Site | Google Scholar
M. Valdés, M. A. Frontini, M. Vázquez, and A. Goossens, “Low-cost 3D nanocomposite solar cells obtained by electrodeposition of ${CuInSe}_{2}$ ,” Applied Surface Science, vol. 254, no. 1, pp. 303–307, 2007.
View at: Publisher Site | Google Scholar
M. Krunks, A. Katerski, T. Dedova, I. Oja Acik, and A. Mere, “Nanostructured solar cell based on spray pyrolysis deposited ZnO nanorod array,” Solar Energy Materials and Solar Cells, vol. 92, no. 9, pp. 1016–1019, 2008.
View at: Publisher Site | Google Scholar
K. Nakaoka, J. Ueyama, and K. Ogura, “Photoelectrochemical behavior of electrodeposited CuO and ${Cu}_{2} O$ thin films on conducting substrates,” Journal of the Electrochemical Society, vol. 151, no. 10, pp. C661–C665, 2004.
View at: Publisher Site | Google Scholar
F. Caballero-Briones, J. M. Artés, I. Díez-Pérez, P. Gorostiza, and F. Sanz, “Direct observation of the valence band edge by in situ ECSTM-ECTS in p-type ${Cu}_{2} O$ layers prepared by copper anodization,” Journal of Physical Chemistry C, vol. 113, no. 3, pp. 1028–1036, 2009.
View at: Publisher Site | Google Scholar
V. P. Dravid, S. Liu, and M. M. Kappes, “Transmission electron microscopy of chromatographically purified solid state $C_{60}$ and $C_{70}$ ,” Chemical Physics Letters, vol. 185, no. 1-2, pp. 75–81, 1991.
View at: Google Scholar
C.-W. Chu, V. Shrotriya, G. Li, and Y. Yang, “Tuning acceptor energy level for efficient charge collection in copper-phthalocyanine-based organic solar cells,” Applied Physics Letters, vol. 88, no. 15, Article ID 153504, 2006.
View at: Publisher Site | Google Scholar

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Copyright © 2010 Ryosuke Motoyoshi et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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