非晶硅太阳电池结构模拟设计

为了从理论上分析提高非晶硅太阳能电池的转化效率,运用微电子和光子结构分析一维器件模拟程序模拟非晶硅太阳电池a-SiC∶H/a-Si∶H/a-Si∶H结构,分析比较了不同前端接触透明导电层的功函数ФITO、禁带宽度、本征层厚度、掺杂浓度、缺陷态密度等因素对太阳电池性能的影响.模拟得到,在功函数达到5.1 eV,禁带宽度1.8 eV,本征层厚度265 nm等最优化条件下,非晶硅太阳能电池转化效率达到9.855%,比一般非晶硅太阳能电池转化效率高近2%.     

Extreme fluxes in solar energetic particle events: Methodological and physical limitations

In this study, all available data on the largest solar proton events (SPEs), or extreme solar energetic particle (SEP) events, for the period from 1561 up to now are analyzed. Under consideration are the observational, methodological and physical problems of energy-spectrum presentation for SEP fluxes (fluences) near the Earth's orbit. Special attention is paid to the study of the distribution function for extreme fluences of SEPs by their sizes. The authors present advances in at least three aspects: 1) a form of the distribution function that was previously obtained from the data for three cycles of solar activity has been completely confirmed by the data for 41 solar cycles; 2) early estimates of extremely large fluences in the past have been critically revised, and their values were found to be overestimated; and 3) extremely large SEP fluxes are shown to obey a probabilistic distribution, so the concept of an “upper limit flux” does not carry any strict physical sense although it serves as an important empirical restriction. SEP fluxes may only be characterized by the relative probabilities of their appearance, and there is a sharp break in the spectrum in the range of large fluences (or low probabilities). It is emphasized that modern observational data and methods of investigation do not allow, for the present, the precise resolution of the problem of the spectrum break or the estimation of the maximum potentialities of solar accelerator(s). This limitation considerably restricts the extrapolation of the obtained results to the past and future for application to the epochs with different levels of solar activity.     

Dry soil diurnal quasi-periodic oscillations in soil 222Rn concentrations

²²²Rn concentrations have been monitored during the dry season in August 2009 and August 2010, in a reworked alluvial-pyroclastic soil of the Pietramelara Plain, in Southern Italy, with the aim of determining the role of atmospheric factors in producing the quasi-periodic oscillations in soil ²²²Rn concentrations reported in the literature. In this study we present the results of a detailed analysis and matching of soil ²²²Rn concentrations, meteorological and solar parameters where the observed oscillations feature a characteristic behavior with second order build-up and depletion limbs, separated by a daily maximum and minimum. All these features are clearly shown to be tied to sunrise and sunset timings and environmental radiative flux regimes. Furthermore, a significant, and previously unreported, second order correlation (r² = 0.73) between daily maximum hourly global radiation and the daily range of soil ²²²Rn concentrations has been detected, allowing estimates of the amplitude of these oscillations to be made from estimated or measured solar radiation data. The correlation has been found to be valid even in the presence of persistent patchy daytime cloudiness. In this case a daytime prolongation of the night-time build up stage and an attenuation or even suppression of daytime depletion is observed (a previously unreported effect). Neither soil cracking, nor precipitation, both suggested in some studies as causative factors for these oscillations, during the dry season appear to be necessary in explaining their occurrence. We also report the results of an artificial shading experiment, conducted in August 2009, that further support this conclusion. As soil ²²²Rn concentrations during the dry season show a characteristic daily cycle, radon monitoring in soils under these conditions necessarily has to be gauged to the timings of the daily maximum and minimum, as well as to the eventual occurrence of cloudiness and to its related effects, in order to avoid erroneous conclusions.     

3He-rich solar flares

A new subgroup of³He rich solar flares is found on reanalysing the global data.³He/H ratio as a function of maximum proton flux at an energy of about 10 MeV shows a break-up of the data into two groups. The first group follows the anticorrelation of³He/H ratio with the proton flux, as expected in the plasma process acceleration models. But the second group has a constant³He/H ratio as a function of maximum proton flux. This is not in conformity with the plasma process models. But this is expected in models where the nuclear spallation reactions are responsible for the production of³He. It is also found that the same break-up into two distinct groups follows if one plots the location of the flares in the solar disc. The first group is more or less confined to the west limb of the Sun, whereas the second group is more widely spread out across the solar disk. Visiting Professor, Tata Institute of Fundamental Research, Bombay, August–September, 1983.     

以太阳为光源测量大气污染物研究中精确跟踪太阳的方法

本文给出了通过计算太阳在天空中移动的轨迹和利用在实验中所采集到的太阳光谱主动精确跟踪太阳的方法,并且通过在以太阳为光源测量大气中污染物浓度的实验研究中的实际应用,证明了该方法的可靠性和实用性.     

Application of stain-etched porous silicon in light emitting diodes and solar cells

Porous silicon/c-Si heterostructures have been formed by the method of stain etching.The properties of light emitting diodes (LED) and solar cells have been studied. The transport mechanism of the diode has been investigated from the current–voltage characteristics measured at different temperatures (296–380 K). A model based on multi-step tunneling of carriers at reverse and low forward bias (<1 V) and on field tunneling across a narrow barrier at higher forward bias (>1.5 V) is proposed for the LED. In the case of the solar cells the porous silicon is formed in between the fingers of the front grid contact. Application of porous silicon in solar cells results in an increase of the short-circuit current and efficiency of the cells by about 30%.     

Photovoltaic and impedance properties of dye-sensitized solar cell based on nature dye from beetroot

The present study involves fabrication and photovoltaic characterization including impedance properties of dye-sensitized solar cells based on natural dye from beetroot. The electrode of the cell was prepared with commercial Fluorine-doped Tin Oxide glass with 100 μm layer of nanostructured TiO₂ whereas, the counter electrode consisted of platinum-coated glass. Fresh juice was extracted from beetroot to use as dye. The dye exhibited high absorption in visible range. Photovoltaic measurements of the solar cell gave a short circuit current density (Jsc) of 130 μA/cm² and an open-circuit voltage (VOC) of 0.38 V under AM 1.5 illumination intensity. The VOC and Jsc showed linear behavior at higher values of illumination intensities. The conductance-voltage, the capacitance-voltage and the series resistance voltage characteristics of the dye solar cell was measured at frequency range from 5 kHz to 5 MHz to study performance of the dye-sensitized solar cells with natural dyes.     

Thermally evaporated CdS/CdTe thin film solar cells: Optimization of CdCl2 evaporation treatment on absorber layer

CdCl₂ treatment is crucial in the fabrication of highly efficient CdS/CdTe thin-film solar cells. This study reports a comprehensive analysis of thermal evaporated CdS/CdTe thin-film solar cells when the CdTe absorber layer is CdCl₂ annealed at temperatures from 340 to 440 °C. Samples were characterized for structural, optical, morphological and electrical properties. The films annealed at 400 °C showed better crystallinity with a cubic zinc blende structure having large grains. Higher refractive index, optical conductivity, and absorption coefficient were recorded for the CdTe films annealed at 400 °C with CdCl₂. Optimum photoactive properties for CdS/CdTe thin-film solar cells were also obtained when samples were annealed at 400 °C for 20 min with CdCl₂, and the best device exhibited V_OC of 668.4 mV, J_SC of 13.6 mA cm⁻², FF of 53.9% and an efficiency of 4.9%.     

Chaotic behavior in stellar dynamos

Slowly rotating main-sequence stars with deep convective zones have activity cycles like the sun's. The solar cycle is aperiodic and modulated to give intervals of reduced activity. A simple sixth-order system, obtained by truncating the dynamo equations, has solutions that mimic this behavior. The transition to chaos is analyzed and the astrophysical significance of these results is discussed.     

A multi-wall carbon nanotube–molecular semiconductor composite for bi-layer organic solar cells

A water-soluble composite of oxidised multi-wall carbon nanotubes and sulphonic acid sodium salt derivatised copper phthalocyanine for application in bi-layer organic solar cells is reported. Measurements of the topography of thin films of this novel material and of the valence electronic structure of its two components are used to rationalise the photovoltaic characteristics of a model organic heterojunction utilising the nanocomposite as the hole-extracting electrode and donor layer.