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Organic photovoltaic cells are now approaching commercially viable efficiencies, particularly for applications that make use of their unique potential for flexibility and semitransparency.sup.1-3. However, their reliability remains a major concern, as even the most stable devices reported so far degrade within only a few years.sup.4-8. This has led to the belief that short operational lifetimes are an intrinsic disadvantage of devices that are fabricated using weakly bonded organic materials--an idea that persists despite the rapid growth and acceptance of organic light-emitting devices, which can achieve lifetimes of several million hours.sup.9. Here we study an extremely stable class of thermally evaporated single-junction organic photovoltaic cells. We accelerated the ageing process by exposing the packaged cells to white-light illumination intensities of up to 37 Suns. The cells maintained more than 87 per cent of their starting efficiency after exposure for more than 68 days. The degradation rate increases superlinearly with intensity, leading to an extrapolated intrinsic lifetime, T.sub.80, of more than 4.9 × 10.sup.7 hours, where T.sub.80 is the time taken for the power conversion efficiency to decrease to 80 per cent of its initial value. This is equivalent to 27,000 years outdoors. Additionally, we subjected a second group of organic photovoltaic cells to 20 Suns of ultraviolet illumination (centred at 365 nanometres) for 848 hours, a dose that would take 1.7 × 10.sup.4 hours (9.3 years) to accumulate outdoors. No efficiency loss was observed over the duration of the test. Overall, we find that organic solar cells packaged in an inert atmosphere can be extremely stable, which is promising for their future use as a practical energy-generation technology. Organic photovoltaic cells containing an intrinsically stable organic absorber layer that are likely to be stable for many decades under illumination are demonstrated., Author(s): Quinn Burlingame [sup.1] , Xiaheng Huang [sup.1] , Xiao Liu [sup.1] , Changyeong Jeong [sup.1] , Caleb Coburn [sup.2] , Stephen R. Forrest [sup.1] [sup.2] [sup.3] Author Affiliations: (1) [...]

Of the many materials and methodologies aimed at producing low-cost, efficient photovoltaic cells, inorganic-organic lead halide perovskite materials (1-17) appear particularly promising for next-generation solar devices owing to their high [...]

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.solener.2010.02.010 Byline: Lanlan Lu (a), Renjie Li (a), Ke Fan (a), Tianyou Peng (a)(b) Keywords: Dye-sensitized solar cell; ZnO film; Annealing temperature; Energy conversion Abstract: Dye-sensitized solar cells (DSSCs) were fabricated by using porous ZnO electrodes derived from home-made ZnO nanoparticles. Electrochemical impedance spectra and open-circuit photovoltage decay curves measurements were performed to investigate the photoelectrochemical characteristics of ZnO films annealed at different temperatures. The experimental results indicate that the effects of the bulk traps and the surface states within the ZnO films on the recombination processes of the photoinjected electrons in DSSCs depend on the annealing temperature. The DSSC based on the ZnO electrode annealed at 400[degrees]C exhibits an optimal energy conversion efficiency of 3.92% under the illumination of one sun simulated sunlight because the farthest decrease in the effects of both bulk traps and surface states at this film can maintain a lower charge recombination probability. This result indicates that the ZnO film electrode has promising application in the field of DSSCs, and the optimization of porous film fabrication condition is efficient for the improvement of ZnO-based DSSC's performances. Author Affiliation: (a) College of Chemistry and Molecular Science, Wuhan University, Wuhan 430072, PR China (b) State Key Laboratory of Rare Earth Materials Chemistry and Applications, Peking University, Beijing 100871, China Article History: Received 29 October 2009; Revised 20 January 2010; Accepted 22 February 2010 Article Note: (miscellaneous) Communicated by: Associate Editor Sam-Shajin Sun

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.solener.2010.01.007 Byline: M. Ben Rabha, B. BessaA[macron]s Keywords: Solar cells; Silicon; Porous silicon; Grooving Abstract: Photovoltaic properties of buried metallic contacts (BMCs) with and without application of a front porous silicon (PS) layer on multicrystalline silicon (mc-Si) solar cells were investigated. A Chemical Vapor Etching (CVE) method was used to perform front PS layer and BMCs of mc-Si solar cells. Good electrical performance for the mc-Si solar cells was observed after combination of BMCs and thin PS films. As a result the current-voltage (I-V) characteristics and the internal quantum efficiency (IQE) were improved, and the effective minority carrier diffusion length (Ln) increases from 75 to 110[mu]m after BMCs achievement. The reflectivity was reduced to 8% in the 450-950nm wavelength range. This simple and low cost technology induces a 12% conversion efficiency (surface area=3.2cm.sup.2). The obtained results indicate that the BMCs improve charge carrier collection while the PS layer passivates the front surface. Author Affiliation: Laboratoire de PhotovoltaA[macron]que, Centre de Recherches et des Technologies de l'Energie, Technopole de Borj-Cedria, BP 95, 2050 Hammam-Lif, Tunisia Article History: Received 24 August 2009; Revised 4 January 2010; Accepted 6 January 2010 Article Note: (miscellaneous) Communicated by: Associate Editor Nicola Romeo

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.solener.2009.12.012 Byline: Gi-Won Lee (a)(b), Donghwan Kim (b), Min Jae Ko (a), Kyungkon Kim (a), Nam-Gyu Park (a)(c) Keywords: Dye-sensitized; Solar cell; Measurement; Absorption range dependence; Mask; Over photocurrent Abstract: We have investigated the change in photocurrent density (J.sub.SC) of dye-sensitized solar cell (DSSC) before and after covering an aperture mask on the cell, especially its dependence on solar absorption range in dye. Four different dyes having absorption threshold at 460nm (P5), 520nm (TA-St-CA), 680nm (N719) and 820nm (N749) are tested. J.sub.SC of the DSSC without mask decreases after mask, where the decreasing rate (a[sup.3]J.sub.SC = J.sub.SC (no mask) -J.sub.SC (with mask)/J.sub.SC (no mask)) becomes larger when dye absorption threshold decreases. a[sup.3]J.sub.SC at the given TiO.sub.2 film thickness of 10[mu]m is determined to be about 20%, 15% and 13% for P5, TA-St-CA and N719-N749, respectively, which is reduced to 14% (TA-St-CA), 11.3% (N719) and 10.5% (N749) after increasing the thickness to 20[mu]m, except for P5 dye remaining unchanged. According to the analysis based on IPCE and photon flux data, the over photocurrents observed for the unmasked dye-sensitized solar cells and their dependence on dye absorption range are found to be attributed to diffuse light leaving the dye-adsorbed TiO.sub.2 active area. Author Affiliation: (a) Solar Cell Research Center, Materials Science and Technology Division, Korea Institute of Science and Technology (KIST), Seoul 136-791, Republic of Korea (b) Department of Material Engineering, Korea University, Seoul 136-701, Republic of Korea (c) School of Chemical Engineering, Sungkyunkwan University, Suwon 440-746, Republic of Korea Article History: Received 25 August 2009; Revised 10 December 2009; Accepted 18 December 2009 Article Note: (miscellaneous) Communicated by: Associated Editor Sam-Shajin Sun

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.solener.2009.08.014 Byline: Santolo Daliento (a), Laura Lancellotti (b) Keywords: Concentrator cell; Series resistance; Numerical simulations Abstract: This paper deals with the modeling of series resistance components in silicon concentrator solar cells. The main components of the macroscopic series resistance are analyzed by means of one-dimensional (1D), two-dimensional (2D), and three-dimensional (3D) numerical simulations. It is shown that the contribution of the lateral current flux, flowing along the emitter region, and of the transverse current flux, flowing along the metal grid, cannot be neglected and, hence, the operation of solar cells subjected to high current densities cannot be described by simple one-dimensional models. The percentage weight of 2D and 3D components on the total value of the series resistance is evaluated and rules for the proper design of the cell geometries are given. An analysis of the effectiveness of the most popular methods for the extraction of the series resistance from the I-V curves of solar cells is also proposed. Author Affiliation: (a) Department of Electronic Engineering and TLC, University of Naples 'Federico II', Via Claudio 21, 80125 Napoli, Italy (b) ENEA Research Center, Localita Granatello, 80055 Portici, Italy Article History: Received 15 April 2009; Revised 29 July 2009; Accepted 16 August 2009 Article Note: (miscellaneous) Communicated by: Associate Editor Igor Tyukhov

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.solener.2009.07.009 Byline: Colin Powell, Timothy Bender, Yuri Lawryshyn Keywords: Organic photovoltaics; Payback period; Cost of production; Large-scale organic solar cells Abstract: Organic solar cells are an emerging photovoltaic technology that is inexpensive and easy to manufacture, despite low efficiency and stability. A model, named TEEOS (Technical and Economic Evaluator for Organic Solar), is presented that evaluates organic solar cells for various solar energy applications in different geographic locations, in terms of two financial indicators, payback period and net present value (NPV). TEEOS uses SMARTS2 software to estimate broadband (280-4000nm) spectral irradiance data and with the use of a cloud modification factor, predicts hourly irradiation in the absence of actual broadband irradiance data, which is scarce for most urban locations. By using the avoided cost of electricity, annual savings are calculated which produce the financial indicators. It is hoped that these financial indicators can help guide certain technical decisions regarding the direction of research for organic solar cells, for example, increasing efficiency or increasing the absorptive wavelength range. A sample calculation using solar hats is shown to be uneconomical, but a good example of large-scale organic PV production. Author Affiliation: Department of Chemical Engineering and Applied Chemistry, Faculty of Engineering and Applied Science, University of Toronto, 200 College Street, Toronto, Ont., Canada M5S 3E5 Article History: Received 16 March 2009; Revised 29 June 2009; Accepted 23 July 2009 Article Note: (miscellaneous) Communicated by: Associate Editor Sam-Shajin Sun

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.solener.2009.06.003 Byline: M. Venkatachalam (a), M.D. Kannan (a), N. Muthukumarasamy (b), S. Prasanna (a), S. Jayakumar (a), R. Balasundaraprabhu (a), M. Saroja (c) Keywords: CIGS; Electron beam deposition; Solar cells Abstract: CIGS bulk with composition of CuIn.sub.0.85Ga.sub.0.15Se.sub.2 was synthesized by direct reaction of elemental copper, indium, gallium and selenium. CIGS thin films were then deposited onto well-cleaned glass substrates using the prepared bulk alloy by electron beam deposition method. The structural properties of the deposited films were studied using X-ray diffraction technique. The as-deposited CIGS films were found to be amorphous. On annealing, the films crystallized with a tetragonal chalcopyrite structure. An intermediate Cu-rich phase precipitated at 200[degrees]C and dissociated at higher annealing temperatures. Average grain size calculated from the XRD spectra indicated that the films had a nano-crystalline structure and was further corroborated by AFM analysis of the sample surface. The chemical constituents present in the deposited CIGS films were identified using energy dispersive X-ray analysis. CIGS based solar cells were then fabricated on molybdenum and ITO coated glass substrates and the efficiencies have been evaluated. Author Affiliation: (a) Thin Film Center, Department of Physics, PSG College of Technology, Coimbatore, India (b) Department of Physics, Coimbatore Institute of Technology, Coimbatore, India (c) Department of Electronics, Erode Arts College, Erode, India Article History: Received 27 April 2008; Revised 20 May 2009; Accepted 3 June 2009 Article Note: (miscellaneous) Communicated by: Associate Editor Takhir Razykov

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.solener.2009.05.009 Byline: G. Peharz, G. Siefer, A.W. Bett Keywords: Spectrum; Monitoring; Spectrometric; Rating; PV; Module Abstract: A method to quantify spectral effects on the electric parameters of multi-junction solar cells is presented. The method is based on measuring the short circuit current of at least two monitor cells. Ideally these monitor cells have the same spectral responses as the subcells in the investigated multi-junction solar cell. In contrast to the subcells, the current of the individual monitor cells can be measured separately. This allows conclusions to be drawn about the spectral impact on the current mismatch of the multi-junction solar cell. A spectrometric evaluation method is then applied. The method has been tested experimentally with three concentrator modules using III-V triple-junction solar cells. These modules were measured outdoors for several months under variable solar spectral conditions. In parallel, the IV curves of the modules and the current of two component cells were measured. A spectral parameter Z was derived from the monitor cell current signals, which was correlated to the short circuit current and the fill factor of the modules. A linear correlation was found between Z and the normalized short circuit current of the concentrator modules. Translation equations were derived from the linear correlation. These enable the calculation of a module's short circuit current under any spectral conditions. In particular, the short circuit currents of the modules were derived for direct normal irradiance of 850W/m.sup.2 and spectral conditions corresponding to the AM1.5d low AOD spectrum. This is an important step towards comparing the performance of modules which show strong spectral sensitivity. Future rating methods can benefit from the presented simple method for quantifying spectral impacts on multi-junction solar cells. Furthermore, the method can be of interest for tuning the spectrum of pulsed solar simulators. Author Affiliation: Fraunhofer-Institut fur Solare Energiesysteme, HeidenhofstraAe 2, 79110 Freiburg, Germany Article History: Received 7 August 2008; Revised 4 May 2009; Accepted 20 May 2009 Article Note: (miscellaneous) Communicated by: Associate Editor Frank Vignola

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.solener.2009.03.015 Byline: Yongsheng Chen (a)(b), Jianhua Wang (b)(c), Shi-e Yang (a), Jingxiao Lu (a), Jinhua Gu (a), Xiaoyong Gao (a), Xuejun Guo (a), Chenhai Shen (a), Weidong Man (c) Keywords: Transient depletion; Microcrystalline silicon; Thin film; Raman crystallinity Abstract: In is paper, the transient behavior of silane molecules in the initial plasma ignition stage on the properties of microcrystalline silicon films is studied using tailored initial SiH.sub.4 density method, and the results are analyzed by Raman spectroscopy and spectroscopic ellipsometry. Compared with standard plasma ignition conditions, tailored initial SiH.sub.4 density conditions result higher crystallinity in the interface between substrate and bulk film. Finally, tailored and standard conditions are used in i-layer deposition processes of p-i-n and n-i-p solar cells. It is demonstrated that tailored initial SiH.sub.4 density conditions is helpful for the efficiency improvement of n-i-p solar cells and standard plasma ignition conditions for p-i-n solar cells. Author Affiliation: (a) Key Laboratory of Material Physics, Department of Physics, Zhengzhou University, College street No. 75 Zhengzhou, Zhengzhou 450052, China (b) Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031, China (c) Department of Materials Science and Engineering, Wuhan Institute of Technology, Wuhan 430073, China Article History: Received 3 September 2008; Accepted 12 March 2009 Article Note: (miscellaneous) Communicated by: Associate Editor Nicola Romeo

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.solener.2008.11.002 Byline: M. Ben Rabha (a), W. Dimassi (b), M. Bouaicha (b), H. Ezzaouia (b), B. Bessais (a) Keywords: Polycrystalline silicon; Porous silicon; Passivation; LBIC mapping; IQE mapping Abstract: In the present work, we report on the effect of introducing a superficial porous silicon (PS) layer on the performance of polycrystalline silicon (pc-Si) solar cells. Laser-beam-induced current (LBIC) mapping shows that the PS treatment on the emitter of pc-Si solar cells improves their quantum response and reduce the grain boundaries (GBs) activity. After the porous silicon treatment, mapping investigation shows an enhancement of the LBIC and the internal quantum efficiency (IQE), due to an improvement of the minority carrier diffusion length and the passivation of recombination centers at the GBs as compared to the reference substrate. It was quantitatively shown that porous silicon treatment can passivate both the grains and GBs. Author Affiliation: (a) Laboratoire de Nanomateriaux et des Systemes pour l'Energie, Centre de Recherches et des Technologies de l'Energie - Technopole de Borj-Cedria BP 95, 2050 Hammam-Lif, Tunisia (b) Laboratoire de photovoltaique, des semiconducteurs et des nanostructures, Centre de Recherches et des Technologies de l'Energie - Technopole de Borj-Cedria BP 95, 2050 Hammam-Lif, Tunisia Article History: Received 23 June 2008; Revised 22 October 2008; Accepted 3 November 2008 Article Note: (miscellaneous) Communicated by: Associate Editor Dr. Takhir Razykov

Cumulative electrostatic discharges (ESDs) on spacecraft solar cells result in the degradation of their performances. In this paper, silicon solar cells are tested in inverted voltage gradient situation obtained in plasma. ESDs occurring on the cells are detected by both electrical and optical signatures. To be representative of flight ESDs, the test setup must avoid unwanted coupling with ground arcs. The degradation is then evaluated by measuring the current--voltage characteristic of the cell in darkness. The equivalent shunt resistance allows quantifying this degradation, which can be attributed to material deposition on the cell edge or to local cell carbonization due to arcing. Visual inspection of the cells allows us to correlate ESD location and local degradation of the cell. The important parameter for solar cell degradation is the amount of energy dissipated during the discharge. A model of the plasma expansion from the cathode spot is compared to measurement. This model explains the current rise during the first phase of the discharge, which is the same for normal ESDs and coupling with ground ESDs. Index Terms--Arcing, electrostatic discharges (ESDs), plasma expansion model, solar cell degradation.

The absorbers are identified for multiple transition solar cells that are implemented with nanostructured heterojunctions. The InAs/GaAsSb is suited for further examination of a quantum dot intermediate-band solar cell.

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.solener.2005.12.004 Byline: N.H. Rafat Keywords: Vertical multi-junction; Solar cell; Edge illumination Abstract: The series connected silicon vertical multi-junctions (VMJs) solar cells have been suggested as means for ensuring high voltage high efficiency solar cells. This study includes a review of some previously published work concerning the edge-illuminated VMJs solar cells. We introduce a simple one-dimensional analysis to study the high voltage series connected silicon VMJs solar cells. The cell, under study, consists of 40 VMJs. Each junction (unit cell) has dimensions of 250[mu]mx0.78cmx500[mu]m. We calculate the short circuit current, the open circuit voltage and the efficiency for an ideal cell, having perfect carrier collection at short circuit conditions, and for real cells. An optimization with respect to the base doping, the emitter doping, the surface recombination velocity and the number of junctions is done for the real cell. A conversion efficiency of 20% has been calculated under AM1.5 light spectrum for real cells having a base doping of 10.sup.16 cm.sup.-3 and an emitter doping of 10.sup.17 cm.sup.-3. Author Affiliation: Department of Mathematics and Engineering Physics, Faculty of Engineering, Cairo University, Giza, Egypt Article History: Received 23 May 2005; Revised 15 November 2005; Accepted 7 December 2005 Article Note: (miscellaneous) Communicated by: Associate Editor T.M. Razykov

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.solener.2005.10.008 Byline: Arturo Morales-Acevedo Keywords: CdTe solar cells; Conversion efficiency; Research perspectives Abstract: Polycrystalline thin film CdTe continues to be a leading material for the development of cost effective and reliable photovoltaics. The two key properties of this material are its band gap (1.5eV), close to the ideal for photovoltaic conversion efficiency (1.45eV), and its high optical absorption coefficient. Thin film CdTe solar cells are typically hetero-junctions with CdS being the n-type partner, or window layer. Efficiencies as high as 16.5% have been achieved, but still there is some potential for increasing them. We make an analysis of the typical CdS/CdTe superstrate solar cell, and from it we establish critical issues and different lines of research in order to improve the current efficiencies. We also show that present record efficiencies are very close to the practical efficiency limit for a CdS/CdTe hetero-junction cell. Author Affiliation: CINVESTAV del IPN, Department of Electrical Engineering, Avenida IPN No. 2508, 07360 Mexico DF, Mexico Article History: Received 16 June 2005; Revised 3 October 2005; Accepted 6 October 2005 Article Note: (miscellaneous) Communicated by: Associate Editor T.M. Razykov

The dye-sensitized solar cells (DSC) were assembled by using natural dyes extracted from black rice, capsicum, erythrina variegata flower, rosa xanthina, and kelp as sensitizers. The [I.sub.Sc] from 1.142 mA to 0.225 mA, the [V.sub.OC] from 0.551 V to 0.412 V, the fill factor from 0.52 to 0.63, and [P.sub.max] from 58 [micro]W to 327 [micro]W were obtained from the DSC sensitized with natural dye extracts. In the extracts of natural fruit, leaves and flower chosen, the black rice extract performed the best photosensitized effect, which was due to the better interaction between the carbonyl and hydroxyl groups of anthocyanin molecule on black rice extract and the surface of Ti[O.sub.2] porous film. The blue-shift of absorption wavelength of the black rice extract in ethanol solution on Ti[O.sub.2] film and the blue-shift phenomenon from absorption spectrum to photoaction spectrum of DSC sensitized with black rice extract are discussed in the paper. Because of the simple preparation technique, widely available and low cheap cost natural dye as an alternative sensitizer for dye-sensitized solar cell is promising. Keywords: Dye-sensitized solar cell; Natural dye; Photosensitizer; Black rice; Anthocyanin; Nanocrystalline Ti[O.sub.2] porous film; Fill factor; Natural pigment

Si-wafers for solar cells were cast in a size of 50 x 46 x 0.5 [mm.sup.3] by a direct casting method. A graphite mold coated by boron nitride (BN) powder was used in order to prevent the reaction between carbon and the molten silicon. Without any coating, the reaction of the Si melt to the graphite mold was very severe. In the case of BN coating, SiC was formed in the shape of tiny islands on the surface of the Si wafer by the reaction between the Si-melt and the carbon of the graphite mold at high temperature. The grain size was about 1 mm. The efficiency of the Si solar cell was about 0.5% under AM1.5 conditions. It was lower than that of a Si solar cell fabricated with a common single- (sc, 3.0%) and poly-crystalline (pc, 1.0%) Si wafer, which showed much lower efficiency than that of other commercial pc- or sc-Si solar cell (10-15%). Keywords: Silicon wafer; Direct casting; BN coating; Si solar cell

Si[N.sub.x]:H anti-reflective coating (ARC) layers were successfully grown by an in-line plasma enhanced chemical vapor deposition (PECVD) system with an extremely high throughput. Film thickness and refractive index of the as-grown samples were evaluated as functions of growth parameters, such as growth pressure, total gas flow rate, radio frequency (RF) power and Si[Hsub.4] to N[H.sub.3] gas ratio. It was found that we could achieve high quality films with proper growth conditions and proper post-deposition annealing. Keywords: In-line PECVD; Si[N.sub.x]:H; Anti-reflection coating; Throughput

Thin films of cadmium oxide (CdO) were synthesized by layer-by-layer deposition method on indium doped tin oxide (ITO) substrates. Post-deposition annealing at 250 [degrees]C for 24 h produced pure phase CdO films by removal of trace amount of cadmium hydroxide, as confirmed from X-ray diffractogram. First time employment of CdO in place of Ti[O.sub.2] in dyesensitized solar cells is reported to check feasibility and cell performance. A dye-sensitized nanocrystalline CdO photo-electrode was obtained by adsorbing cis-dithiocyanato (4,4'-dicarboxylic acid-2,2'-bipyridide) ruthenium (II) (N3) dye by keeping at 45 [degrees]C for 20 h. The efficiency of dye-sensitized nanocrystalline CdO thin film solar cell was increased from 0.24% to 2.95% due to dye adsorption. This must be highest reported conversion efficiency for other metal oxides than Ti[O.sub.2]based dye-sensitized solar cells. Keywords: Thin films; Cadmium oxide; Morphology; Structural properties; Dye-sensitized solar cell

CIGS films were prepared on Mo-coated glass by sputtering and selenization processes. The metallic precursors were selenized under higher pressure in selenium vapor instead of [H.sub.2]Se. In order to improve the performance of CIGS thin film solar cells, the morphologies of CIGS thin films were studied carefully by various temperature profiles. The relationship between temperature decrease rate and fill factor (FF) of solar ceils was investigated thoroughly. On the other hand the value of open circuit voltage ([V.sub.oc]) was improved by increasing the gallium content near the surface of CIGS thin film. A glass/Mo/CIGS/CdS/ZnO cell was fabricated and the conversion efficiency of 9.4% was obtained without antireflective film. Keywords: Selenization; CIGS solar cell; Solid Se source

R.F. sputter deposition of Sb doped CdTe thin films was carried out with targets containing different amounts of antimony ([C.sub.T]: 0, 2.5, 10 and 20 at.%). The substrates were kept at different temperatures ([T.sub.s]) of 200, 275, 350 and 450 [degrees]C. Three different argon pressure values: 2.5, 5 and 15 mTorr were used. The lowest dark resistivity (p) at room temperature (RT) was 9.0 x [10.sup.5] [omega] cm, which is one of the lowest values reported in the literature for Sb doped CdTe. Highly transparent (~90%) and conductive (p = 3.7 x [10.sup.-4] [omega] cm) F doped CdO (n-type) thin films, prepared at room temperature by the sol-gel method, were employed as window and top-contact. The configuration of the fabricated solar cell was (Au-Cu)/p-CdTe/n-CdO/glass. Open-circuit voltage ([V.sub.oc]) and short-circuit current density ([J.sub.sc]) at room temperature have the highest values for high [T.sub.s], low [P.sub.g] and [C.sub.T] = 10 at.%. Despite the fact that [V.sub.oc] and [J.sub.sc] are lower than those reported in the literature, we think this work is useful as a basis for the search of more competitive CdTe/ CdO based PV devices. Keywords: Thin films; Solar cells; Growth parameters

Charge transport properties of the Schottky diodes fabricated on n-CdTe layers electrodeposited on stainless steel foil are investigated. The small area Au-CdTe contacts facilitated the investigation of the role of shunt and series resistances on the I-V characteristics of the thin-film CdTe device. The charge transport mechanism in these diodes is found to be generation-recombination in the depletion layer and over-barrier electron flow at low and higher bias voltages, respectively. By using this model a quantitative theoretical analysis of the current-voltage characteristics of the diodes is possible. Keywords: Solar cells; CdTe; Electrodeposition; Charge transport

Recently, the clean electric power generation systems have attracted a great deal of social attention to exploit the clean-energy resources such as solar arrays, wind generators, fuel cells, and so forth. In this case, a multiple-input dc--dc converter is useful to combine the several input power sources and to supply the regulated output voltage for the load from the power sources. The novel solar-cell power supply system using the buck--boost-type two-input dc--dc converter is proposed, in which a solar array and a commercial ac line are employed as power sources and are combined by two input windings of the energy-storage reactor. Also, its operation principle and performance characteristics are discussed. Furthermore, the solar-cell optimum-operating-point tracker is proposed and examined. It is confirmed by the experiment that the proposed solar-cell power supply system has excellent performance characteristics. Index Terms--DC--DC converter, multiple-input, optimum operating, phase shift, solar array.

Thin CuIn[S.sub.2] films were prepared by sulfurization of Cu/In bi-layers. First, the precursor layer was electroplated onto the treated surface of Mo-coated glass. Observation of the cross-section prepared by focused ion beam (FIB) etching revealed that the void-free film was initially formed on the top surface of the precursor layer and continued to grow until the advancing front of the film reached the Mo layer. The nucleation of voids near the bottom of the CuIn[S.sub.2] film followed. To determine whether the condition of the Cu/In alloy influences the CuIn[S.sub.2] quality we investigated the Cu/In alloy state using FIB. We found that the annealed precursor of low Cu/In ratio (1.2) has several voids in the mid position in the layer compared with Cu-rich precursor (1.6). The cross-sectional view of the Cu-rich absorber layer is uniform compared with the low copper absorber layer. Thin film solar cells were fabricated using the CuIn[S.sub.2] film (Cu/In ratio: 1.2) as an optical absorber layer. It was found that the optimization of a sulfurization period is important in order to improve the cell efficiency. We have not yet obtained good results with high Cu-rich absorber because of a blister problem. This blister was found before sulfurization. So, we are going to solve this blister problem before sulfurization. Keywords: CuIn[S.sub.2]; Thin film; Electroplating; Sulfurization; Solar cell; Focused ion beam

The influence of the overlap of the three absorption coefficients on the efficiency of the intermediate band solar cell (IBSC) is studied. It is concluded that in contrast with the single gap solar cell in the radiative limit, the thickness of the ISBC becomes a parameter to be optimized.

A model for the analysis of interference reflection data of nanoporous TiO2 dye-sensitized solar cells (DSSC) is presented. It is shown that the interference reflection technique allows one to monitor very precisely the evolution of the depletion layer of the fluor-doped SnO2 (FTO) conducting substrate at the DSSC back contact with the position of the Fermi level.

Analysis of efficient solar cells shows that the contributions of the counter electrode to the energy losses are larger than expected. Correlations between 2-electrode and 3-electrode measurements provide information regarding the quality of the counter electrode and possible potential drops in the systems.

The application of the drift-diffusion model for the illustration of the operation of the quantum dot intermediate band solar cell (QD-IBSC) and its validity limits are described. The conditions of small contribution of the electron and hole drift currents in comparison to the total current are discussed.

Rapid thermal firing (RTF) of screen-printed contacts, with high heating and cooling rates, is found to improve String Ribbon solar cell efficiency. Such screen-printed String Ribbon cells with independently confirmed efficiencies as high as 14.7% are achieved through an understanding and implementation of hydrogen passivation of defects.