在夹心结构-Si:H膜中的反常光电导响应

在不同场强和照度下,测量了一系列夹心结构-Si∶H膜的光电导响应曲线,发现在较弱场强下,上升曲线和下降曲线有反常现象。作者分析了光电导响应曲线,指出无论是上升曲线还是下降曲线,都可以分解为由两个变化过程组成:一个尖形和一个类指数形。通过对零场和极弱场强响应的研究,表明上述现象可用光照或停止光照后空间电荷分布的变化来解释。本文对具有低迁移率和高电阻率的光敏材料具有普遍的意义。     

非晶硅光电导响应的动力学研究(Ⅰ)强电场下的光电导响应

本文从动力学的观点出发,研究了各种条件下的光电导响应,以及有关的效应。本篇只讨论强电场下的光电导响应。 我们测量了不同照度和电场下的瞬态响应,发现强光区,在一定强电场下,时间常数0随照度F的-0.5次方变化(0=F-0.5)。弱光区时间常数不变,在一定照度下,上升时间随电场指数变化;下降时间不变。由于晶体中的一些概念已不适用于非晶硅的情况,我们从Mott-CFO模型出发,用速率方程推导出弱光和强光照射下的光电导响应公式,较好地解释了实验结果。     

Mapping photovoltaic performance with nanoscale resolution

Photo‐conductive AFM spectroscopy (‘pcAFMs’) is proposed as a high‐resolution approach for investigating nanostructured photovoltaics, uniquely providing nanoscale maps of photovoltaic (PV) performance parameters such as the short circuit current, open circuit voltage, maximum power, or fill factor. The method is demonstrated with a stack of 21 images acquired during in situ illumination of micropatterned polycrystalline CdTe/CdS, providing more than 42 000 I/V curves spatially separated by ~5 nm. For these CdTe/CdS microcells, the calculated photoconduction ranges from 0 to 700 picoSiemens (pS) upon illumination with ~1.6 suns, depending on location and biasing conditions. Mean short circuit currents of 2 pA, maximum powers of 0.5 pW, and fill factors of 30% are determined. The mean voltage at which the detected photocurrent is zero is determined to be 0.7 V. Significantly, enhancements and reductions in these more commonly macroscopic PV performance metrics are observed to correlate with certain grains and grain boundaries, and are confirmed to be independent of topography. These results demonstrate the benefits of nanoscale resolved PV functional measurements, reiterate the importance of microstructural control down to the nanoscale for 'PV devices, and provide a widely applicable new approach for directly investigating PV materials. Copyright © 2015 John Wiley & Sons, Ltd.     

Amorphous silicon-based unipolar detector for color recognition

The device performance of a novel color sensitive diode (p-i-i-i-n-diode)-based on amorphous silicon is discussed. The detectors are developed with regard to the μτ-(carrier mobility×lifetime)-product and the bandgap of the different i-layers resulting in a voltage controlled spectral response. Since the linear independence of the spectral response curves and a linear response of the photocurrent on the incident light intensity is a prerequisite for the generation of a red-green-blue signal, the influence of light intensity on the color separation is examined by spectral response measurements under different monochromatic bias illumination. Additionally, numerical simulations are carried out to study the optoelectronic properties of these devices. Finally, a deconvolution method is presented which allows the transformation of the measured spectral response curves into a red-green-blue signal     

太阳电池IV曲线中一种新光电流泄露机制研究

本论文详细分析了光伏器件中的光电流泄露机制,并在传统单二极管模型基础上,提出了一种新的分析模型以解释太阳电池研究过程中的一些异常IV曲线。新模型中主要考虑了一种位置相关的光电流泄露路径。两个具有明显电流扩展效应的GaInP太阳电池被用来研究光电流的泄露机制。这种新发展的分析模型可以很好的用来解释电池在非均匀辐照下的IV曲线,并提取了有效扩展电阻等重要电池参数。最后文中也强调了实际分析过程中的单二极管模型失效条件。论文中所使用的分析方法也适用于分析均匀光照下的IV曲线的侧向电压分布分析。     

A Back-Illuminated Vertical-Structure Ultraviolet Photodetector Based on an RF-Sputtered ZnO Film

A back-illuminated vertical-structure ZnO ultraviolet (UV) detector was fabricated using an indium-tin oxide (ITO) electrode. Ordered ITO and ZnO films were grown on a quartz substrate by radiofrequency sputtering. At 5 V bias, the dark current was 640 μA and the photocurrent was 16.8 mA under UV illumination (365 nm, 10 μW), indicating a high responsivity of 1616 A/W. The response time measurements showed a rise time of 71.2 ns and a decay time of 377 μs. The ZnO detector performed well and can be used in a focal-plane array for UV image detection.     

Electrical performance increase of concentrator solar cells under Gaussian temperature profiles

Linear solar concentrators focus radiation onto the solar cell achieving a Gaussian illumination profile. Most of these concentrators use an active cooling system to evacuate the energy not converted into electricity to avoid undesirable overheating. Heat sinks can cause different temperature profiles in the cell depending on the cooling mechanism. Two temperature patterns are most common: the Gaussian and the anti‐Gaussian. The effect of these temperature curves on the cell's electrical parameters has been analysed and characterised numerically and experimentally under different concentrated radiations. A power output increase is shown when the cell is subjected to a Gaussian temperature profile. Contrarily, the cell efficiency decreases more than 3% under the anti‐Gaussian temperature profile. It is demonstrated that it is possible to tailor the temperature profile to maximise voltage output for determined illumination conditions. Copyright © 2011 John Wiley & Sons, Ltd.     

Study of the color detection of a-Si:H by transient response in thevisible range

A new technique of color detection based on time-resolved charge collection during transient response measurement using a hydrogenated amorphous silicon detector has been proposed and experimentally demonstrated. The method based on the material intrinsic wavelength-filtering properties is implemented in color sensing by transient response of a detector to a combination of basic color light and voltage pulse. Resulting transient responses under different illumination and bias voltage conditions confirm considerable accuracy of proposed method. In particular, the best agreement of measured and calculated transient response curves has been obtained by using the spectral response of all three primary colors in calculations. It was observed that the presence of blue light drastically reduces the transient response to a chromatic light illumination. Finally, a voltage pulse influence to the basic colors transient response was found     

Calculations and effects of inhomgeneity in compensated photoconductors

Our calculations of the conductivity inhomogeneity in high resistivity photoconductors prepared by the impurity compensation technique, show that this inhomogeneity is generally large and could exceed that in the starting material by several orders of magnitude. The amount of this inhomogeneity is shown, however, to be not only a function of the inhomogeneity in the starting material and the uniformity of the impurity diffusion, but also of both the compensation conditions and the operating temperature. Due to this sample inhomogeneity the lifetime variation within a sample may reach up to several orders of magnitude, particularly at low temperatures and illumination intensities. Our theoretical study shows that large degrees of inhomogeneity change the apparent electronic behaviour of the material in the following ways: (i) deviation in the normal resistivity or Hall effect versus temperature relationships, (ii) anomalous variation in the steady state photoconductivity with illumination intensity and with temperature, and deviations from exponentiality in the photoconductivity decay curves, and (iii) distortion of the thermally stimulated conductivity (TSC) curves, including the possible appearance of several peaks even in the presence of only a single trap. A comparison of the accuracy of the different methods that may be used in the analysis of the TSC measurements shows that the initial rise method combined with several decayed TSC measurements are indispensible, and are the only techniques which together could yield reliable conclusions about the trapping structure when significant inhomogeneity is present. Finally, experimental results illustrating the above mentioned effects are presented for the case of zinc-compensated silicon photoconductors.     

-Si∶H膜中反常瞬态响应的光谱影响

测量夹心结构-Si∶H膜的瞬态响应谱时,发现无论是在低的正向偏压还是在低的反向偏压下,起始部分都出现不正常的尖形脉冲,它的幅度随光波长的增长而减小。零场瞬态谱的研究表明,这种不正常的非传输部分来源于结区,它的升降特点决定于光照时的空间电荷限制光电流。从光电流幅值与光吸收系数的关系式,我们发展了一种确定光学隙的方法。