The photovoltaic effect of the p–n heterojunction organic photovoltaic device using a nano template method

Characteristics of ITO/polypyrrole (PPy) nano fibers/poly(3-hexylthiophene)/Al photovoltaic devices prepared by nano template method were studied. PPy nano fibers on ITO glass were formed through nano pores of polymer membrane template using home made special sample holder by electrochemical polymerization in an electrolyte solution of pyrrole and lithium perchlorate as a dopant in acetonitrile. Ordered structure with enhanced interfacial area formed by nano template method enable to fabricate polymeric photovoltaic device with improved photo-conversion efficiency. This nano fiber structures film possesses increased interfacial area, large charge separation area (photoactive zone) and secured charge transportation route. The effect of altering energy levels of PPy by changing doped state was also studied. Device made with nano fiber structure showed enhanced photovoltaic effect than that of overlayed film device.     

Electron transport simulation in bulk wurtzite ZnO and its n+–n–n+ diode,compared with GaN

We study the electron transport within bulk wurtzite ZnO and its n⁺–n–n⁺ diode by the Ensemble Monte Carlo method. In bulk ZnO we study the steady state and transient situation with three valley model for the conduction band and compare the results with GaN. Our results show that ZnO's threshold field occurs at a higher applied electric field than GaN. Also, velocity overshoot in ZnO occurs at higher electric fields, too. But the overshoot relaxation time is about 0.3 ps for both of them. As the results show, the role of the third valley is tiny, so for a diode we use two valley conduction bands. For anode voltage ranges from 0.25 to 3 V, we simulate the profiles of the electron density, electric field, potential, average electron velocity, and compare the results with that for GaN. Our results show, as we expect, electron velocity in active layer in the GaN diode is faster than in ZnO.     

TEM-based phase retrieval of p–n junction wafers using the transport of intensity equation

Two cross-sectional specimens of pattered silicon wafers implanted with either arsenic or phosphor are investigated in the transmission electron microscope (TEM). Phase retrieval using the transport of intensity equation (TIE) is suggested as a means for nano-scale sensing of dopants in such p--n junction wafers. Improvements in TIE phase retrieval are proposed and implemented using a through-focus series of large numbers of images. Polynomial fitting to robustly estimate the required intensity defocus-derivative is shown to enhance data quality, resulting in phase maps that portray detail over a broad range of spatial-frequencies in a realistic manner.     

Preparation and photovoltaic property of a new hybrid nanocrystalline SnO2/Polypyrrole p–n heterojunction

Hybrid photovoltaic structures based on transparent conductive SnO₂ and electrically conductive polypyrrole (PPy) were prepared. Nanocrystalline SnO₂ is considered an n-type barrier and window layer on p-type PPy layer in cell structures. The surface morphology and thickness of the layers were studied using scanning electron microscopy. The optical absorbance data showed an increase of absorbance in contrast with PPy and SnO₂. There was a red shift in absorbance wavelengths and a decrease in band gaps for the prepared PV structures. To investigate the electrical properties of the obtained structures, current-voltage characteristic was measured. The best structure showed an open-circuit voltage of 0.170?V, a short-circuit current density of 0.017?mA/cm², a fill factor of 0.36 and power conversion efficiency of 0.076.     

Measurement of PV asymmetry in +p→d+γ and ■+d→n+p

The measurement of parity-violating (PV) observables in few-nucleon system can shed light on our current understanding of the weak interaction between nucleons.Theoretical models describe the nucleonnucleon weak interaction at low energies use a series of undetermined parameters.Two parity violating measurements have been considered: the capture of polarized slow neutrons on hydrogen (n + p → d + γ) at Los Alamos National Laboratory for first phase and Oka Ridge National Laboratory for second phase and the helicity dependence of the deuteron photodisintegration cross section using circularly polarized photons (γ + d → n + p) at Shanghai Institute of Applied Physics.The goal of both experiments is to constraint the weak meson-nucleon couplings to a precision of 1 ×10-8 .The introduction of both experiments is presented.     

Non-monotonic dependence of current upon i-width in silicon p–i–n diodes

Silicon p–i–n diodes with different i-region widths are fabricated and tested. It is found that the current shows the non-monotonic behavior as a function of i-region width at a bias voltage of 1.0 V. In this paper, an analytical model is presented to explain the non-monotonic behavior, which mainly takes into account the diffusion current and recombination current contributing to the total current. The calculation results indicate that the concentration ratio of p-region to n-region plays a crucial role in the non-monotonic behavior, and the carrier lifetime also has a great influence on this abnormal phenomenon.     

Measurement of PV asymmetry in(→n)+p→d+γ and (→γ)+d→n+p

The measurement of parity-violating(PV)observables in few-nucleon system can shed light on our current understanding of the week interaction between nucleons.Theoretical models describe the nucleonnucleon weak interaction at low energies use a series of undetermined parameters.Two parity violating measurements have been considered: the capture of polarized slow neutrons on hydrogen((n)+p→d+γ)at Los Alamos National Laboratory for first phase and Oka Ridge National Laboratory for second phase and the helicity dependence of the deuteron photodisintegration cross section using circularly polarized photons((γ)+d→n+p*)at Shanghai Institute of Applied Physics.The goal of both experiments is to constraint the weak meson-nucleon couplings to a precision of 1 × 10-8.The introduction of both experiments is presented.     

Study of the Isospin Mixing in 6Li with α + p + n Three-Body Model

We calculate the isospin mixing probabilities for both T = 0 and T = 1 states of ⁶Li systematically, and compare them to clarify the relation between the structure of ⁶Li and the isospin mixing probabilities. As a result, the effect of halo structure on the isospin mixing cannot be seen clearly. The effect of the coupling to the continuum states such as of ⁵He + p and ⁵Li + n is suggested.     

Effect of violating t-invariance of the electromagnetic interaction of hadrons in the processes n + p → d + γ and n + → d + e++e−

T-odd correlations that are possible in the processes n + p d + and n + p d + e⁺ + e^e- and that arise due to the capture of thermal neutrons are determined in terms of threshold amplitudes (for the process n + p d + @#@) or electromagnetic inelastic form factors (for the process n + p d+ e⁺ + e^e§-). The mechanism of these reactions is not given in concrete form, but those general properties of the electromagnetic hadronic current are used that are preserved with three-dimensional reflections.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 8–13, October, 1986.     

Optical and current transport properties of CuO/ZnO nanocoral p–n heterostructure hydrothermally synthesized at low temperature

We demonstrate the synthesis and investigate the electrical and optical characteristics of ‘nanocorals’ (NCs) composed of CuO/ZnO grown at low temperature through the hydrothermal approach. High-density CuO nanostructures (NSs) were selectively grown on ZnO nanorods (NRs). The synthesized NCs were used to fabricate p–n heterojunctions that were investigated by the current density–voltage (J–V) and the capacitance–voltage (C–V) techniques. It was found that the NC heterojunctions exhibit a well-defined diode behavior with a threshold voltage of about 1.52 V and relatively high rectification factor of ～760. The detailed forward J–V characteristics revealed that the current transport is controlled by an ohmic behavior for V≤0.15 V, whereas at moderate voltages 1.46≤V<1.5 the current follows a J? α?exp(βV) relationship. At higher voltages (≥1.5 V) the current follows the relation J? α? V ², indicating that the space-charge-limited current mechanism is the dominant current transport. The C–V measurement indicated that the NC diode has an abrupt junction. The grown CuO/ZnO NCs exhibited a broad light absorption range that is covering the UV and the entire visible parts of the spectrum.     

Enhanced absorption process in the thin active region of GaAs based p–i–n structure

The optical absorption is the most important macroscopic process to characterize the microscopic optical transition in the semiconductor materials. Recently, great enhancement has been observed in the absorption of the active region within a p–n junction. In this paper, Ga As based p–i–n samples with the active region varied from 100 nm to 3 μm were fabricated and it was observed that the external quantum efficiencies are higher than the typical results, indicating a new mechanism beyond the established theories. We proposed a theoretical model about the abnormal optical absorption process in the active region within a strong electric field, which might provide new theories for the design of the solar cells,photodetectors, and other photoelectric devices.     

Numerical simulation of the magnetoresistance effect controlled by electric field in p–n junction

The magnetoresistance effect of a p–n junction under an electric field which is introduced by the gate voltage at room temperature is investigated by simulation. As auxiliary models, the Lombardi CVT model and carrier generationrecombination model are introduced into a drift-diffusion transport model and carrier continuity equations. All the equations are discretized by the finite-difference method and the box integration method and then solved by Newton iteration.Taking advantage of those models and methods, an abrupt junction with uniform doping is studied systematically, and the magnetoresistance as a function of doping concentration, SiO_2 thickness and geometrical size is also investigated. The simulation results show that the magnetoresistance(MR) can be controlled substantially by the gate and is dependent on the polarity of the magnetic field.     

High operating temperature SWIR p+–n FPA based on MBE-grown HgCdTe/Si(0 1 3)

The characteristics of SWIR (1.6–3 μm) 320 × 256 and 1024 × 1024 focal plane arrays (FPA’s) based on n-type In-doped HgCdTe heteroepitaxial layers are reported. The HgCdTe layers were grown by molecular beam epitaxy on silicon substrates with ZnTe and CdTe buffer layers. p–n junctions were formed by arsenic ion implantation into HgCdTe film. Reverse current in the temperature range from 210 to 330 K was found to be limited by the diffusion mechanism. At the same time in the temperature range from 140 to 210 K the reverse current was dominated by the thermal generation of charge carriers through deep traps located in the middle of the band gap. At 170 K NETD was less than 40 mK.     

Description of the gamov-teller β+-decays and (n,p) transitions in spherical nuclei

The results of calculations of the total log (t)-quantities for decays of neutron-deficit nuclei and strength functions of (n, p) transitions are presented. It is shown that in spherical nuclei the ¦g _A/g _V¦1·0 conditions hold for the constants of a weak interaction.Dedicated to the memory of M. Gmitro.