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Sheet Resistance (sheet + resistance)
Selected AbstractsMetal Ion Implantation for the Fabrication of Stretchable Electrodes on ElastomersADVANCED FUNCTIONAL MATERIALS, Issue 3 2009Samuel Rosset Abstract Here, the use of low-energy metal ion implantation by filtered cathodic vacuum arc to create highly deformable electrodes on polydimethylsiloxane (PDMS) membranes is reported. Implantation leads to the creation of nanometer-size clusters in the first 50,nm below the surface. When the elastomer is stretched, these small clusters can move relative to one another, maintaining electrical conduction at strains of up to 175%. Sheet resistance versus ion dose, resistance versus strain, time stability of the resistance, and the impact of implantation on the elastomer's Young's modulus are investigated for gold, palladium, and titanium implantations. Of the three tested metals, gold has the best performance, combining low and stable surface resistance, very high strain capabilities before loss of electrical conduction, and low impact on the Young's modulus of the PDMS membrane. These electrodes are cyclically strained to 30% for more than 105 cycles and remain conductive. In contrast, sputtered or evaporate metals films cease to conduct at strains of order 3%. Additionally, metal ion implantation allows for creating semi-transparent electrodes. The optical transmission through 25-µm-thick PDMS membranes decreases from 90% to 60% for Pd implantations at doses used to make stretchable electrodes. The implantation technique presented here allows the rapid production of reliable stretchable electrodes for a number of applications, including dielectric elastomer actuators and foldable or rollable electronics. [source] Preparation and characterization of transparent PANI-SIO2 hybrid conducting filmsPOLYMER ENGINEERING & SCIENCE, Issue 5 2010Li Wei Dodecylbenzene sulfonic acid-doped polyaniline (DBSA-PANI) was prepared with 3-glycidoxypropyltrimethoxysilane (GPTMS) through a sol,gel route without water and ethanol. Acetic acid was used to play both the roles of reagent and catalyst during the hydrolysis-condensation reaction of GPTMS, which affected the structure of precursors. On the other hand, m -cresol can adjust the acidity of solution and it was also a secondary dopant in DBSA-PANI to enhance conductivity of hybrid films. The conductivity and visible light transmittance vary with the molar ratio of acetic acid to GPTMS and m -cresol to GPTMS. Sheet resistance of the new hybrid films made by a dipping process reaches 5.1 k,/, and visible light transmittance is higher than 75%. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers [source] Spin- and Spray-Deposited Single-Walled Carbon-Nanotube Electrodes for Organic Solar CellsADVANCED FUNCTIONAL MATERIALS, Issue 14 2010Sungsoo Kim Abstract Organic bulk-heterojunction solar cells using thin-film single-walled carbon-nanotube (SWCNT) anodes deposited on glass are reported. Two types of SWCNT films are investigated: spin-coated films from dichloroethane (DCE), and spray-coated films from deionized water using sodium dodecyl sulphate (SDS) or sodium dodecyl benzene sulphonate (SDBS) as the surfactant. All of the films are found to be mechanically robust, with no tendency to delaminate from the underlying substrate during handling. Acid treatment with HNO3 yields high conductivities >1000,S,cm,1 for all of the films, with values of up to 7694,±,800,S,cm,1 being obtained when using SDS as the surfactant. Sheet resistances of around 100,,,sq,1 are obtained at reasonable transmission, for example, 128,±,2,,,sq,1 at 90% for DCE, 57,±,3,,,sq,1 at 65% for H2O:SDS, and 68,±,5,,,sq,1 at 70% for H2O:SDBS. Solar cells are fabricated by successively coating the SWCNT films with poly(3,4-ethylenedioxythiophene):poly(styrene sulphonate) (PEDOT:PSS), a blend of regioregular poly(3-hexylthiophene) (P3HT) and 1-(3-methoxy-carbonyl)-propyl-1-phenyl-(6,6)C61 (PCBM), and LiF/Al. The resultant devices have respective power conversions of 2.3, 2.2 and 1.2% for DCE, H2O:SDS and H2O:SDBS, with the first two being at a virtual parity with reference devices using ITO-coated glass as the anode (2.3%). [source] Physical properties of Dy and La doped SnO2 thin films prepared by a cost effective vapour deposition techniqueCRYSTAL RESEARCH AND TECHNOLOGY, Issue 10 2006J. Joseph Abstract Stannous oxide (SnO2) thin film is one of the most widely used n-type transparent semi-conductor films in electronics, electro-optics and solar energy conversion. By achieving controlled non-stoichiometry, we can get good transparency and high electrical conductivity simultaneously in SnO2 thin films. Dy and La doped SnO2 thin films have been prepared by a cost effective vapour deposition technique. The structural, photo-electronic, optical and electrical properties of the doped and undoped films were studied. The results of X-ray Diffraction studies reveals the polycrystalline nature of the films with preferential orientation along the (101), (211) and (301) planes and their average grain size variation for different deposition temperature. Photoconductivity and Photovoltaic studies of the films were also performed. The optical properties of these films were studied by measuring their optical transmission as a function of wavelength. The optical transmission is found to be increased on Dy doping and decreased on La doping. The band gap, refractive index and thickness of the films were calculated from U-V transmittance and Absorption graphs. The optical band gap of undoped film is found to be 4.08 eV, but on doping it shifts to lower energies and then increases on increasing the concentration of both dopants. Its electrical parameters such as sheet resistance, resistivity, mobility, Hall coefficient, and carrier concentration were determined by Four Probe, Van der Pauw and Hall Probe method. On doping with Dy, carrier conversion takes place from n-type to p-type and p-conductivity dominates. On La doping no carrier conversion takes place but resistivity decreases. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Conductance Enhancement Mechanisms of Printable Nanoparticulate Indium Tin Oxide (ITO) Layers for Application in Organic Electronic Devices,ADVANCED ENGINEERING MATERIALS, Issue 4 2009Michael Gross We present and discuss several methods to enhance the electrical properties of nanoparticle dispersion derived ITO-layers. A maximum conductance of 132,,,1,cm,1 was achieved and films with a sheet resistance down to 5,,/, were produced. To demonstrate their applicability as electrodes in optoelectronic elements we assembled functioning polymer LED-s on them. [source] Oxygen-Terminated Nanocrystalline Diamond Film as an Efficient Anode in PhotovoltaicsADVANCED FUNCTIONAL MATERIALS, Issue 8 2010Candy Haley Yi Xuan Lim Abstract The potential of using p-doped nanocrystalline diamond as the anode for organic solar cells, because of its outstanding photostability and well-matched energetics with organic dyes, is demonstrated. The interface dipole and open-circuit potential can be tuned by varying the surface termination on diamond. Oxygenated nanocrystalline diamond (O-NCD) exhibits the best photocurrent conversion among all the surface-treated electrodes studied in this work because of its large open-circuit potential. The good energy alignment of the valence band of O-NCD with the HOMO of poly(3-hexylthiophene), as well as its p-doped characteristics, suggest that O-NCD can replace the hole transport layer, such as PEDOT:PSS, needed for efficient performance on indium tin oxide (ITO) electrodes. If the sheet resistance and optical transparency on NCD can be further optimized, chemical-vapor-deposited diamond electrodes may offer a viable alternative to ITO and fluorinated tin oxide (FTO). [source] Efficient Reduction of Graphite Oxide by Sodium Borohydride and Its Effect on Electrical ConductanceADVANCED FUNCTIONAL MATERIALS, Issue 12 2009Hyeon-Jin Shin Abstract The conductivity of graphite oxide films is modulated using reducing agents. It is found that the sheet resistance of graphite oxide film reduced using sodium borohydride (NaBH4) is much lower than that of films reduced using hydrazine (N2H4). This is attributed to the formation of CN groups in the N2H4 case, which may act as donors compensating the hole carriers in reduced graphite oxide. In the case of NaBH4 reduction, the interlayer distance is first slightly expanded by the formation of intermediate boron oxide complexes and then contracted by the gradual removal of carbonyl and hydroxyl groups along with the boron oxide complexes. The fabricated conducting film comprising a NaBH4 -reduced graphite oxide reveals a sheet resistance comparable to that of dispersed graphene. [source] Atomistic analysis of B clustering and mobility degradation in highly B-doped junctionsINTERNATIONAL JOURNAL OF NUMERICAL MODELLING: ELECTRONIC NETWORKS, DEVICES AND FIELDS, Issue 4-5 2010Maria Aboy Abstract In this paper we discuss from an atomistic point of view some of the issues involved in the modeling of electrical characteristics evolution in silicon devices as a result of ion implantation and annealing processes in silicon. In particular, evolution of electrically active dose, sheet resistance and hole mobility has been investigated for high B concentration profiles in pre-amorphized Si. For this purpose, Hall measurements combined with atomistic kinetic Monte Carlo atomistic simulations have been performed. An apparent anomalous behavior has been observed for the evolution of the active dose and the sheet resistance, in contrast to opposite trend evolutions reported previously. Our results indicate that this anomalous behavior is due to large variations in hole mobility with active dopant concentration, much larger than that associated to the classical dependence of hole mobility with carrier concentration. Simulations suggest that hole mobility is significantly degraded by the presence of a large concentration of boron-interstitial clusters, indicating the existence of an additional scattering mechanism. Copyright © 2009 John Wiley & Sons, Ltd. [source] Room-Temperature Conducting LaNiO3 Thick-Film Coatings Prepared by Aerosol DepositionJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2008Jong-Jin Choi Metallic conductive LaNiO3 thick films with a thickness of 0.5,10 ,m were fabricated by a room-temperature-operating powder deposition process,aerosol deposition method. The coated LaNiO3 layers were fairly dense without pores or cracks, and maintained their phase stability due to low-temperature consolidation. The as-deposited LaNiO3 film consisted of ,10-nm-diameter grains, with a sheet resistance of 10,100 ,/,, while the post-annealed LaNiO3 film had a sheet resistance of 4.45 ,/,, which is the lowest value ever reported for an LaNiO3 film. This excellent conductivity result was attributed to the high crystal stability and dense microstructure. [source] Electrical resistance variation of carbon-nanotube networks due to surface modification of glass substratePHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 8 2010Eui Yun Jang Abstract This study presents the effect of the wettability between a glass substrate and carbon-nanotube (CNT) colloidal solution on the density of CNT networks in a dip-coating process. The surface roughness and the density of functional groups of the glass substrate were modified by using an oxygen-plasma treatment, and then we observed the density of CNT networks with respect to different surface conditions due to the surface modification. It is confirmed that the surface chemical property and the surface morphology of the glass substrate determines the density of CNT networks formed by the dip-coating method. The change of surface free energy induced by hydroxylation and hydration enhances the wettability between a glass substrate and CNT colloidal solution. Moreover, the effective area on which silanol groups can be formed is dependent on the roughness of the surface of the substrate. Eventually, the change of the surface free energy due to the hydroxylation, hydration, and surface roughness effect on the density of the coated CNTs, which determines the sheet resistance of CNT networks. [source] Surface treatments of indium-tin oxide substrates for polymer electroluminescent devicesPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 15 2006Z. Y. Zhong Abstract In this work, three different sets of processing techniques (wet, dry, and combined treatments) were utilized to modify the surfaces of indium-tin oxide (ITO) substrates for polymer electroluminescent devices (PELDs), and the influence of surface treatments on the surface properties of ITO substrates were investigated by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), contact angle, and four-point probe. The surface energies of ITO substrates were also calculated from the measured contact angles. Experimental results show that the surface properties of the ITO substrates strongly depend on the surface treatments. Oxygen plasma treatment effectively improves the ITO surface properties since plasma decreases the surface roughness and sheet resistance, improves the surface stoichiometry and wetting. Furthermore, the PELDs with the differently treated ITO substrates as hole-injecting electrodes were fabricated and characterized. We observe that the optical and electrical characteristics of devices are greatly influenced by the surface treatments on ITO substrates. Oxygen plasma treatment decreases turn-on voltage, increases brightness and efficiency, and thereby improves the device performance of PELDs. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Strain-engineered novel III,N electronic devices with high quality dielectric/semiconductor interfacesPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 1 2003M. Asif Khan Abstract Since the early demonstration of 2D-electron gas [M. A. Khan et al., Appl. Phys. Lett. 60, 3027 (1992)] and a heterojunction field effect transistor (HFET) [M. Asif Khan et al., Appl. Phys. Lett. 63, 1214 (1993)] in III,N materials, rapid progress has been made to improve the DC and RF performance of GaN,AlGaN based HFETs. Stable and impressive microwave powers as high as 4,8 W/mm have been reported for device operation frequencies from 10 to 35 GHz. The key reason for these high performance numbers is an extremely large sheet carrier densities (>1 × 1013 cm,2) that can be induced at the interfaces in III,N hetereojunction [A. Bykhovsk et al., J. Appl. Phys. 74, 6734 (1993); M. Asif Khan et al., Appl. Phys. Lett. 75, 2806 (1999)]. These are instrumental in screening the channel dislocations thereby retaining large room temperature carrier mobilities (>1500 cm2/Vs) and sheet resistance as low as 300 ,/sq. These numbers and the high breakdown voltages of the large bandgap III,N material system thus enable rf-power approximately 5,10 times of that possible with GaAs and other competitor's technologies. We have recently introduced a unique pulsed atomic layer epitaxy approach to deposit AlN buffer layers and AlN/AlGaN superlattices [J. Zhang et al., Appl. Phys. Lett. 79, 925 (2001); J. P. Zhang et al., Appl. Phys. Lett. 80, 3542 (2002)] to manage strain and decrease the dislocation densities in high Al-content III,N layers. This has enabled us to significantly improve GaN/AlGaN hetereojunctions and the device isolation. The resulting low defect layers are not only key to improving the electronic but also deep ultraviolet light-emitting diode devices. For deep UV LED's they enabled us to obtain peak optical powers as high as 10 mW and 3 mW for wavelengths as short as 320 nm and 278 nm. Building on our past work [M. Asif Khan et al., Appl. Phys. Lett. 77, 1339 (2000); X. Hu et al., Appl. Phys. Lett. 79, 2832 (2001)] we have now deposited high quality SiO2/Si3N4 films over AlGaN with low interface state densities. They have then been used to demonstrate III,N insulating gate transistors (MOSHFET (SiO2) and MISHFET (Si3N4) with gate leakage currents 4,6 order less than those for conventional GaN,AlGaN HFETs. The introduction of the thin insulator layers (less then 100 Å) under the gate increases the threshold voltage by 2,3 V. In addition, it reduces the peak transconductance gm. However the unity cut-off frequency, the gain and the rf-powers remain unaffected as the gm/Cgs (gate-source capacitance) ratio remains unchanged. In addition to managing the defects and gate leakage currents we have also employed InGaN channel double heterojunction structures (AlInGaN,InGaN,GaN) to confine the carriers thereby reducing the spillover into trappings states. These InGaN based MOS-DHFETs exhibited no current-collapse, extremely low gate leakage currents (<10,10 A/mm) and 10,26 GHz rf-powers in excess of 6 W/mm. We have also demonstrated the scalability and stable operation of our new and innovative InGaN based insulating gate heterojunction field effect transistor approach. In this paper we will review the III,N heterojunction field-effect transistors progress and pioneering innovations including the excellent work from several research groups around the world. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Insertion loss and linearity of III-nitride microwave switchesPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 10 2010Jianyu Deng Abstract We report the insertion loss and linearity characteristics of novel microwave switches based on III-Nitride heterostructure field-effect transistors (HFETs) and Metal-Oxide-Semiconductor HFETs (MOSHFETs). The high mobility and large sheet carrier density make nitride-based microwave switches ideal candidates for high power, low loss and high linearity microwave switching applications. The demonstrated SPDT switch achieved the third order intermodulation power of -68 dBm for 250 micron devices at 1 GHz and 10 dBM input power and the extrapolated IP3 of >80 dBm with <0.25 dB insertion loss and >35 dB isolation for 2GHz operation for 3mm devices. Further improvements of the insertion loss and linearity are expected from new material and contact development, which will achieve lower 2DEG sheet resistance and contact resistance. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Optimization of the ohmic contact processing in InAlN//GaN high electron mobility transistors for lower temperature of annealingPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 1 2010Karol Abstract In this article, we optimized the ohmic contact processing in InAlN/GaN high electron mobility transistors for the lower temperature of annealing by recessing of metalliza-tion to approach the 2DEG at the InAlN/GaN interface. The ohmic contacts which were recessed down to 5 nm depth and annealed at 700 °C 2 min. exhibited the contact resistance of 0,39 ,mm while the channel sheet resistance was 210 ,/square. These values are comparative to values of contacts processed at more conventional an-nealing conditions (800 °C, 2 min). Moreover we applied the recessed ohmic contact technology to fabricate Schottky barrier (SB) HEMTs and MOSHEMTs with Al2O3 dielectric film. For MOSHEMTs, we measured the maximal reduction of the gate leakage current by about 6 orders of magnitude if compared with SB HEMTs. The maximal drain current of MOSHEMTs was about 750 mA/mm at VGS = 0 V and the maximal extrinsic transconductance (gme) reached 101 mS/mm. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Enhancement in electrical properties of GaN heterostructure field-effect transistor by Si atom deposition on AlGaN barrier surfacePHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue S2 2009Norio Onojima Abstract This study demonstrates that deposition of Si atoms on AlGaN barrier surfaces in GaN heterostructure field-effect transistors (HFETs) can modulate the electrical properties of the two-dimensional electron gas (2DEG). The results of Hall measurements performed using the eddy current and four-point van der Pauw methods showed that the sheet resistance of an AlGaN/GaN HFET sample without surface passivation increased from that of the unprocessed sample after post-metallization annealing at 820 °C for ohmic contacts. In contrast, the sheet resistance of the Si-deposited sample did not increase even after annealing. Furthermore, eddy current measurements for unprocessed wafers with and without Si deposition revealed that the sheet resistance can be reduced by depositing Si atoms, regardless of annealing. The effect of Si deposition on devices having a thin Al-rich barrier layer was found to be significant. The deposition of Si atoms (2 nm) on the AlN barrier surface in an AlN/GaN HFET (AlN 2 nm) resulted in a remarkable decrease in the sheet resistance from 60356 to 388 ,/sq. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Processing approaches of AlGaN/GaN Metal Insulator Semiconductor Hetero Field Effect Transistors (MISHFET) on Si (111) substratesPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue S2 2009Martin Eickelkamp Abstract We report on the fabrication of AlGaN/GaN MISHFETs using SiO2 and SiN as gate dielectrics. In particular, two different passivation procedures are investigated with respect to the resulting electrical properties. A fluorine based ICP etch step, as used here to remove the gate dielectric prior to passivation layer deposition, is shown to deteriorate the sheet carrier concentration and mobility. Depositing the passivation layer upon the gate dielectric, on the other hand, slightly decreases the sheet resistance as compared to a conventional HFET. Gate diode characteristics reveal significant reduction of gate leakage currents in both, reverse and forward biasing regions, of 1-2 and up to 6 orders of magnitude, respectively. All devices exhibit more pronounced current collapse compared to a conventional passivated HFET. In addition, a clear depencency on the processing scheme is observed. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Analysis of electrical properties of insulators (Si3N4, SiO2, AlN, and Al2O3)/0.5 nm Si3N4/AlGaN/GaN heterostructuresPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2007Narihiko Maeda Abstract The electrical properties in AlGaN/GaN heterostructures with Si- and Al-based insulators (Si3N4, SiO2, AlN, and Al2O3) have been examined and analyzed. By insulators deposition, significant increase in the two-dimensional electron gas (2DEG) density (Ns) was observed with the order of Ns(Al2O3) > Ns(AlN) , Ns(SiO2) > Ns(Si3N4) > N0 (N0: Ns without insulators). As the result, the decrease in the sheet resistance (R) was observed; the smallest order of R was R(Al2O3) < R(AlN) < R(Si3N4) < R0 , R(SiO2) (R0: R without insulator). The insulators deposition effect has thus been shown to be significant and different among insulators. The increase in Ns was analyzed in terms of the change in the potential profile, and the observed differences in Ns among insulators have been interpreted. The band engineering including insulators is indispensable in understanding and designing AlGaN/GaN HFETs, since insulators are commonly used for the surface passivation as well as for the gate insulators, and the insulators deposition is to alter the essential device parameters such as the source resistance. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Study of the activation process of Mg dopant in GaN:Mg layersPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 3 2006B. Paszkiewicz Abstract GaN:Mg layers with different concentration of Mg dopant were grown by metalorganic vapour phase epitaxy. The incorporation of Mg was verified by secondary ion mass spectroscopy. In order to dissociate Mg-related complexes and thus electrically activate the acceptor dopant, the as-grown layers were annealed in pure N2 at ,800 °C for 30 minutes. The influence of the post-growth annealing on the layer properties was studied by photoluminescence (PL) and impedance spectroscopy. Impedance spectroscopy measurement showed that the annealed samples reveal higher charge concentrations and lower sheet resistance. Moreover, the relaxation time of hole traps decreased in annealed samples by one order of magnitude compared to as-grown samples. The changes in the electrical properties have been correlated with the changes in the PL spectra. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] High Productive Deposited Mo Layers for Back Ohmic Contacts of Solar CellsPLASMA PROCESSES AND POLYMERS, Issue S1 2009Jens-Peter Heinß Abstract In the paper, thin molybdenum (Mo) layers produced by magnetron sputtering [state of the art in production for photovoltaic applications (PV)] are compared with those produced by high-rate electron beam (EB) deposition technology. Stainless steel and borofloat glass served as substrate materials. Mo layers deposited by DC-magnetron sputtering were produced as a reference and investigated by analysis of structure and specific electrical resistance. Alternative layers prepared by high-rate EB-deposition with a rate up to 240,nm·s,1 were characterised by inquests of mechanical properties, sheet resistance and cell efficiency. A strong dependency of specific electrical resistance on residual gas conditions was determined. The specific electrical resistance dropped from 18 to 11,µ,·cm. Compactness of Mo layers increased with implementation of plasma activation. The layer formation became denser and comparable to the magnetron sputtered Mo layers. [source] Influence from front contact sheet resistance on extracted diode parameters in CIGS solar cellsPROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 2 2008Ulf Malm Abstract The extraction of one-diode model parameters from a current,voltage (J,V) curve is problematic, since the model is one-dimensional while real devices are indeed three-dimensional. The parameters obtained by fitting the model curve to experimental data depend on how the current is collected, and more specifically the geometry of the contact. This is due to the non-uniform lateral current flow in the window layers, which leads to different parts of the device experiencing different front contact voltage drop, and hence different operating points on the ideal J,V curve. In this work, finite element simulations of three-dimensional contact structures are performed and compared to experimental data on Cu(In,Ga)Se2 -based solar cell devices. It is concluded that the lateral current flow can influence the extracted parameters from the one-diode model significantly if the resistivity of the front contact material is high, or if there is no current collecting grid structure. These types of situations may appear in damp heat-treated cells and module type cells, respectively. Copyright © 2007 John Wiley & Sons, Ltd. [source] Optimizing the diffused regions of interdigitated backside buried contact solar cellsPROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 3 2007Jiun-Hua Guo Abstract Recombination and a number of other important factors must be considered in the optimization of the diffused regions of high-efficiency silicon solar cells. In this paper, we examine issues related to the four types of diffusions used in rear-junction, interdigitated backside buried contact solar cells made on n-type silicon wafers: the phosphorus-diffused front-surface field (FSF), the boron-diffused emitter, and the boron and the phosphorus diffused contact regions. Dark saturation current density, effective lifetime, implied open-circuit voltage and sheet resistance are characterized for the optimization of the above-mentioned diffused regions. Diffusion uniformity and the avoidance of the diffusion-induced dislocations are also discussed for the heavily diffused, metal coated contact diffusions. It is found that the optimal sheet resistances of the FSF for planar and textured surfaces are 120,,/, and 105,,/, respectively, whereas the optimal post-processing sheet resistance for the boron emitter is approximately 100,,/,. Moreover, sheet resistance as heavy as 10,20,,/, for the boron groove diffusion and 5,10,,/, for the phosphorus groove diffusion have been achieved without introducing the diffusion-induced misfit dislocations. Careful consideration of the issues discussed here led to an absolute efficiency improvement on the planar n-type IBBC solar cell of more than 0·6%. Copyright © 2006 John Wiley & Sons, Ltd. [source] Flexible, Stretchable, Transparent Conducting Films Made from Superaligned Carbon NanotubesADVANCED FUNCTIONAL MATERIALS, Issue 6 2010Chen Feng Abstract A straightforward roll-to-roll process for fabricating flexible and stretchable superaligned carbon nanotube films as transparent conducting films is demonstrated. Practical touch panels assembled by using these carbon nanotube conducting films are superior in flexibility and wearability,and comparable in linearity,to touch panels based on indium tin oxide (ITO) films. After suitable laser trimming and deposition of Ni and Au metal, the carbon nanotube film possesses excellent performance with two typical values of sheet resistances and transmittances (208,, ,,1, 90% and 24,, ,,1, 83.4%), which are comparable to ITO films and better than the present carbon nanotube conducting films in literature. The results provide a route to produce transparent conducting films more easily, effectively, and cheaply, an important step for realizing industrial-scale applications of carbon nanotubes for transparent conducting films. [source] Electron transport properties of low sheet-resistance two-dimensional electron gases in ultrathin AlN/GaN heterojunctions grown by MBEPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2008Yu Cao Abstract A study of the transport properties of polarizationinduced 2DEGs at MBE-grown single AlN/GaN heterostructures with different growth rates is reported. It is observed that faster growth rates lead to high mobilities, approaching , 1600 cm2/Vs at 300 K and , 6000 cm2/Vs at low temperatures for ultrathin (2.3 nm AlN/GaN) heterojunctions. By using a theoretical model in conjunction with experimentally measured transport properties, it is concluded that the 300 K sheet resistances of very high density 2DEGs at AlN/GaN heterojunctions are currently limited (, 170 , /,) by interface roughness scattering, and can be further reduced by improving the growth conditions. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Formation of Boron-doped region using spin-on dopant: investigation on the impact of metallic impuritiesPROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 5 2008J. Jourdan Abstract Investigation on the electrical properties of p+ -doped regions formed by spin-on-dopant (SOD) technique was achieved. Using this technique, boron-diffused regions were formed on both p-type and n-type float zone wafers. Homogeneous sheet resistances were obtained for both types of wafers. Bulk properties were investigated by measuring effective carrier lifetime. An iron contamination was observed after the boron diffusion step and interstitial iron concentrations were deduced from lifetime measurements. More investigations proved that the iron was initially present within the SOD film. A phosphorus diffusion allows to remove this bulk contamination, leading to an improvement of effective lifetime values. Nevertheless, the corresponding emitter saturation current density was estimated on n-type wafers and presented a high value. It is likely that this poor electrical quality is the consequence of a high iron concentration which remains in the diffused region. Some possibilities are suggested to avoid or to limit this contamination. Copyright © 2008 John Wiley & Sons, Ltd. [source] Screen-print selective diffusions for high-efficiency industrial silicon solar cellsPROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 1 2008Matthew Edwards Abstract Screen-print diffusion pastes present an industrially applicable alternative to conventional techniques of dopant deposition. Several commercially available screen-print dopant pastes are assessed for their suitability in forming heavy selective diffusions for use under metal contacts in silicon solar cells. Pastes are assessed in terms of their ease of application, their ability to form heavy diffusions with low sheet resistances, and their ability to maintain high post-diffusion wafer lifetimes. Potential for the use of dopant pastes in high-efficiency solar cell devices is investigated using photoconductance (PC) measurements and photoluminescence (PL) images. It is found that under certain conditions, screen-print dopant pastes, particularly phosphorus paste, have potential to form effective selective diffusions without significantly compromising performance in high-efficiency solar cells. Copyright © 2007 John Wiley & Sons, Ltd. [source] Optimizing the diffused regions of interdigitated backside buried contact solar cellsPROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 3 2007Jiun-Hua Guo Abstract Recombination and a number of other important factors must be considered in the optimization of the diffused regions of high-efficiency silicon solar cells. In this paper, we examine issues related to the four types of diffusions used in rear-junction, interdigitated backside buried contact solar cells made on n-type silicon wafers: the phosphorus-diffused front-surface field (FSF), the boron-diffused emitter, and the boron and the phosphorus diffused contact regions. Dark saturation current density, effective lifetime, implied open-circuit voltage and sheet resistance are characterized for the optimization of the above-mentioned diffused regions. Diffusion uniformity and the avoidance of the diffusion-induced dislocations are also discussed for the heavily diffused, metal coated contact diffusions. It is found that the optimal sheet resistances of the FSF for planar and textured surfaces are 120,,/, and 105,,/, respectively, whereas the optimal post-processing sheet resistance for the boron emitter is approximately 100,,/,. Moreover, sheet resistance as heavy as 10,20,,/, for the boron groove diffusion and 5,10,,/, for the phosphorus groove diffusion have been achieved without introducing the diffusion-induced misfit dislocations. Careful consideration of the issues discussed here led to an absolute efficiency improvement on the planar n-type IBBC solar cell of more than 0·6%. Copyright © 2006 John Wiley & Sons, Ltd. [source] | ||||||||||||||||