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N Junction (n + junction)

Distribution by Scientific Domains
Physics and Astronomy40%

Selected Abstracts

One-Dimensional Microwires Formed by the Co-Assembly of Complementary Aromatic Donors and Acceptors

ADVANCED FUNCTIONAL MATERIALS, Issue 11 2009
Jie-Yu Wang
Abstract A truxene derivative (Tr3) with a C3 symmetric conjugated plane is synthesized; this derivative is a perfect match, in both size and structure, with its oxidized counterpart, the truxenone derivative (TrO3), a new electron acceptor that was recently reported. The complementary pair, Tr3 and TrO3, sets a good platform for the investigation of aromatic donor,acceptor interactions. Detailed 1H NMR experiments, photoluminescence spectroscopy, as well as differential scanning calorimetry are performed to investigate the interaction between Tr3 and TrO3, from solution to mesophase. One-dimensional microbelts readily formed from a 1:1 mixture of Tr3 and TrO3. Scanning electron microscopy, powder X-ray diffraction, as well as fluorescence microscopy are performed to elucidate their co-assembly structure in the solid state. Moreover, modulation of the co-assembly structure is easily realized by changing the concentration or mixing ratio. The present system opens the possibility of forming 1D heterostructures via electron donor,acceptor interaction, and its potential application as P,N junction and photowaveguide materials in optoelectronic devices. [source]

p,n-Junction-Based Flexible Dye-Sensitized Solar Cells

ADVANCED FUNCTIONAL MATERIALS, Issue 2 2010
Liping Heng
Abstract In this paper, a new type of flexible working electrode, TiO2/CuI/Cu, is reported, in which the p,n junction of TiO2,CuI is introduced into dye-sensitized solar cells (DSSCs) for the first time. The devices give a high conversion efficiency of up to 4.73% under 1 sun illumination. The excellent performance is ascribed to the existence of the p,n junction, which forms a single directional pathway for electron transport which benefits the charge separation, and improves the efficiency of the flexible solar cells as a result. [source]

Off-axis electron holography of electrostatic potentials in unbiased and reverse biased focused ion beam milled semiconductor devices

JOURNAL OF MICROSCOPY, Issue 3 2004
A. C. TWITCHETT
Summary Off-axis electron holography in the transmission electron microscope (TEM) is used to measure two-dimensional electrostatic potentials in both unbiased and reverse biased silicon specimens that each contain a single p,n junction. All the specimens are prepared for examination in the TEM using focused ion beam (FIB) milling. The in situ electrical biasing experiments make use of a novel specimen geometry, which is based on a combination of cleaving and FIB milling. The design and construction of an electrical biasing holder are described, and the effects of TEM specimen preparation on the electrostatic potential in the specimen, as well as on fringing fields beyond the specimen surface, are assessed. [source]

Laser-doping of silicon carbide for p,n junction and LED fabrication

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 4 2007
Sachin Bet
Abstract The high melting point and the limited diffusion of impurities in silicon carbide have greatly restricted the use of conventional ion implantation and furnace to incorporate and activate dopants. A laser doping technique overcomes these obstacles for doping silicon carbide and other wide band gap semiconductors. This paper presents the work on fabrication of p,n junction diodes and blue light emitting diodes using laser doping technique. A p,n junction was created by laser doping a silicon carbide wafer with aluminum (p-type) and nitrogen (n-type). Optical interferometer profilometer scan showed that there was no damage on the surface post laser doping. Secondary ion mass spectrometry (SIMS) was carried to estimate the dopant concentration and depth. The effects of laser doping on the current,voltage characteristics were studied. The junctions were characterized by capacitance,voltage and electroluminescence measurements. A broad electroluminescence peak was observed around 498.8 nm wavelength, characterizing the p,n junction as a blue light-emitting diode. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Room temperature electroluminescence from multilayer GeSi heterostructures

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 6 2006
A. A. Tonkikh
Abstract Details of silicon diodes with Ge/Si multilayer quantum dot heterostructures embedded in the Si p,n junction grown by molecular beam epitaxy emitting in the range of 1.4,1.7 µm at room temperature and continuous injection pumping are discussed. Output power of the light emitting diode reaches 1 µW/cm2 at applied current density of 2 A/cm2. Photoluminescence and transmission electron microscopy show that the origin of intense luminescence is defect free stacked Ge quantum dot array formed inside the structure. It is shown that doping by antimony improves structure quality and increases photoluminescence efficiency at room temperature. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Development of thin-film Cu(In,Ga)Se2 and CdTe solar cells

PROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 2-3 2004
A. Romeo
Abstract Cu(In,Ga)Se2 and CdTe heterojunction solar cells grown on rigid (glass) or flexible foil substrates require p -type absorber layers of optimum optoelectronic properties and n -type wide-bandgap partner layers to form the p,n junction. Transparent conducting oxide and specific metal layers are used for front and back electrical contacts. Efficiencies of solar cells depend on various deposition methods as they control the optoelectronic properties of the layers and interfaces. Certain treatments, such as addition of Na in Cu(In,Ga)Se2 and CdCl2 treatment of CdTe have a direct influence on the electronic properties of the absorber layers and efficiency of solar cells. Processes for the development of superstrate and substrate solar cells are reviewed. Copyright © 2004 John Wiley & Sons, Ltd. [source]

Characterisation of CuInS2/ Zn(Se,O)/ZnO solar cells as a function of Zn(Se,O) buffer deposition kinetics in a chemical bath

PROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 7 2002
A. M. Chaparro
Thin-film solar cells of CuInS2/Zn(Se,O)/ZnO configuration have been studied from the point of view of their dependence on the Zn(Se,O) chemical bath deposition (CBD) conditions. The kinetics of deposition of the Zn(Se,O) buffer is followed during cell processing with a quartz crystal microbalance (QCM). Two different CBD growth mechanisms yield buffer layers with different properties. Under a predominant electroless deposition reaction, the resulting buffer layer has mixed ZnSe,ZnO composition. The solar cells with this buffer type show higher fill factor (FF) and lower open-circuit voltage (Voc). Under a chemical growth regime, the buffer layer has higher ZnSe proportion, giving rise to cells with higher VOC, but lower FF and stability. The parameters of this second type of cell also show major dependence on illumination effects (light-soaking effects). Electron-beam-induced current (EBIC) and cathodoluminescence (CL) measurements are carried out to characterise the CuInS2/Zn(Se,O) junctions formed under the two buffer growth regimes. Cross-sectional EBIC shows a wider space charge region (SCR) than expected for p-CuInS2 in contact with Zn(Se,O), and the p,n junction is driven within the CuInS2 phase. These results reflect a chemical modification of CuInS2, most probably caused by the ammonia of the bath solution. CL shows more defective interfaces when Zn(Se,O) is deposited under the chemical mechanism (slower deposition rate, hence longer contact time of the CuInS2 with the bath solution) than under the electroless kinetics (faster deposition rate). Copyright © 2002 John Wiley & Sons, Ltd. [source]

Impact of Ground-State Charge Transfer and Polarization Energy Change on Energy Band Offsets at Donor/Acceptor Interface in Organic Photovoltaics

ADVANCED FUNCTIONAL MATERIALS, Issue 5 2010
Kouki Akaike
Abstract The fullerene (C60)/copper phthalocyanine (CuPc) interface is one of the widely used donor/acceptor (DA) interfaces for organic photovoltaics (OPVs), and information on the electronic structure at the interface is essential for fully understanding the energetics of excitons and carriers in OPVs. Here, an investigation into the energy levels at the C60/CuPc interface is made using UV photoelectron, X-ray photoelectron, and inverse photoemission spectroscopies. The vacuum level and core levels rise with C60 deposition on the CuPc film, which indicates that the interfacial dipole is formed with the negative charge on the C60 side. The interfacial dipole can be formed by the electron transfer from CuPc to C60 in the ground state at the interface, which is indicated by the analysis of the UV,vis,NIR absorption spectrum of the CuPc/C60 blended film. On the other hand, the highest occupied and lowest unoccupied molecular orbitals of CuPc and C60 shift in opposite directions at the interface. This is attributed to the changes of the polarization energies of CuPc and C60 at the interface. The formation of the interfacial dipole and the change of the polarization energy result in the anomalous energy band offsets at the C60/CuPc interface, which are entirely different from those in inorganic p,n junctions. [source]

Influence of laser shock waves on As implanted HgCdTe

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 4 2007
V. Yakovyna
Abstract The principal purpose of our research is to show that low-temperature treatment of materials can be successfully used instead of annealing. Laser shock waves (LSW) were chosen as an alternative to form p-n junctions in HgCdTe after arsenic ions were implanted. Electrical characteristics of As implanted HgCdTe bulk crystals were studied to determine the effect of LSW generated by nanosecond laser irradiation pulses. The samples were of n -type conductivity immediately after the implantation. Then LSW processing was performed under increasingly growing laser beam power density and shock wave pressure. The experiment demonstrated that a threshold shock wave pressure should be reached to ensure the p -to- n conductivity conversion in the surface layer of samples. On the whole the results provide evidence that LSW combined with ion implantation can be used to form p - n junctions in HgCdTe. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]