QE、LBIC和I-V对铸造多晶硅、单晶硅太阳电池的表征

分析了三种不同类型的商业太阳电池片-P 型铸造多晶硅太阳电池，定边喂膜生长硅(EFG)太阳电池 和单晶硅太阳电池的光谱响应（外量子效率EQE），光束诱导电流（LBIC）和暗电流-电压(I-V)，光照I-V 曲线。在I-V 特性测试中，利用太阳电池的二极管等效模型从测量数据中得出重要的电池参数，例如串联 电阻，并联电阻，二极管理想因子，暗饱和电流等。通过光谱响应和LBIC 测试，分析影响这些参数的可 能性缺陷。在铸造多晶硅、EGF 太阳电池中影响电池参数的主要缺陷是晶界以及位错以及材料中杂质，而 对于单晶硅来说，主要的却是存在于体内的金属杂质等。     

光束诱导电压成像研究

在光束诱导电流（Light Beam Induced Current,简称LBIC）成像技术的基础上,我们从理论和实验上分析了光束诱导电压（Light Beam Induced Voltage,简称LBIV）成像的机理。通过建立光束诱导电压成像的理论模型,认为光束诱导电压成像的测量值是一个平衡电压值,而不是光照区域的局域开路电压,我们在一块复合分布不均匀的单晶硅太阳能电池上验证了这个结论。这为改进光束诱导成像技术奠定了基础。     

Experimental analysis and computer simulation of a methodology for laser focusing in the solar cell characterization by laser beam induced current

This paper presents a quick methodology for focusing a laser beam on a photoactive surface based on performing a single line scan while simultaneously modifying the laser's position over the surface and the distance between the focusing lens and the active surface. The methodology was tested using the computer simulation technique. Several configurations were computer simulated by programming different experimental situations to discover the situations in which this focusing methodology would provide optimum results. The conclusions obtained from computer simulation methodology were checked by means of experimental tests using several solar cells, such as a thin-film amorphous silicon solar cell, a monocrystalline silicon solar cell, and a polycrystalline silicon solar cell. From the tests performed, we concluded that optimum focusing is achieved in systems in which the laser beam induced current signal generated by the photoactive surface has no large heterogeneities (e.g., fingers or grain boundaries), artefacts, or defects. Thus, the best results are achieved in systems where the surface of the photovoltaic device has a certain degree of homogeneity.     

Electron Beam-Induced Current (EBIC) in solution-processed solar cells

Electron Beam-Induced Current (EBIC) measurements were used to produce 2D maps for investigating the homogeneity of solar cells. These maps are acquired by scanning the electron beam of a scanning electron microscope over a small area and using a programmable sample stage to move the solar cell under the scan area. The electron beam generates electron-hole pairs in the solar cell much like light does in normal solar cell operation. Solution-processed solar cells where the active layer consisted of purely inorganic or purely organic materials were measured. Since the electron beam irreversibly damages organic material, it was important to ensure that the measurements were made before the materials were altered.     

Improvements to differential voltage contrast and light and electron scanning beam analysis of solar cells

Differential voltage contrast (DVC) in conjunction with light and electron beam scanning (LEBEAMS) technique were used for measuring the electric potential, field, and charge distribution in solar cells. The DVC is based on enhancement or retardation of secondary electron emission, generated by an electron beam, due to local changes in the potential of a semiconductor device. The information provided by this technique is invaluable to the development of any device. Solar cells have been studied by the DVC technique, both under electrical bias (DVC) and under illumination (DVC in conjunction with LEBEAMS); however, the conditions of the previous did not replicate the normal illumination conditions of a solar cell. The goal of this research was to redesign and expand the previous LEBEAMS experiments to produce accurate profiles of quasi Fermi energies on solar cells.     

Study on the effect of measuring methods on incident photon-to-electron conversion efficiency of dye-sensitized solar cells by home-made setup

An experimental setup is built for the measurement of monochromatic incident photon-to-electron conversion efficiency (IPCE) of solar cells. With this setup, three kinds of IPCE measuring methods as well as the convenient switching between them are achieved. The setup can also measure the response time and waveform of the short-circuit current of solar cell. Using this setup, IPCE results of dye-sensitized solar cells (DSCs) are determined and compared under different illumination conditions with each method. It is found that the IPCE values measured by AC method involving the lock-in technique are sincerely influenced by modulation frequency and bias illumination. Measurements of the response time and waveform of short-circuit current have revealed that this effect can be explained by the slow response of DSCs. To get accurate IPCE values by this method, the measurement should be carried out with a low modulation frequency and under bias illumination. The IPCE values measured by DC method under the bias light illumination will be disturbed since the short-circuit current increased with time continuously due to the temperature rise of DSC. Therefore, temperature control of DSC is considered necessary for IPCE measurement especially in DC method with bias light illumination. Additionally, high bias light intensity (>2?sun) is found to decrease the IPCE values due to the ion transport limitation of the electrolyte.     

太阳光栅光谱仪方案设计

简述了光谱仪的原理、阶梯光栅的基本原理和光栅光谱仪的特性参数。针对目前国内正在研制的光纤阵列太阳光学望远镜,提供了一种太阳光栅光谱仪结构的设计方案。根据太阳光栅光谱仪接收整个太阳光谱的要求,该方案采用了双狭缝设计。根据太阳光栅光谱仪尺寸大、分辨率高、色散大的特点,该设计方案采用了白瞳设计,并对结构中各个元件的选择进行简要阐述。光谱仪采用光纤接入,光栅工作在准Littrow角条件下,以获得高衍射效率,同时辅以棱镜增大横向色散,分开重叠的光谱级次。整个系统结构简单紧凑,可以有效地缩小光谱仪尺寸。     

Design,realization and uncertainty analysis of a laser-based primary calibration facility for solar cells at PTB

A completely newly designed multi-functional facility for the primary calibration of reference solar cells and the spectral characterization of all solar cell types has been developed and built at PTB. The new facility is based on the successfully applied Differential Spectral Responsivity (DSR) method that allows the determination of the absolute spectral responsivity and nonlinearity of solar cells with the lowest uncertainties. By using a tunable laser system, the new setup avoids the main problem of monochromator-based systems: the low optical power level of the monochromatic beam. Thus it enables a significant reduction of the uncertainty for the short circuit current under standard test conditions I_STC of solar cells. It enables the calibration of World Photovoltaic Scale (WPVS) reference solar cells with an uncertainty of 0.4% (k = 2), the lowest value stated by any WPVS laboratory.     

自适应多量程的太阳电池参数测试系统的研究

为了能获取真正的开路电压与短路电流,自动适应多种规格的太阳电池片的参数要求,对太阳电池的测试的电子模型与自适应多测试系统进行研究。首先在分析原有太阳电池测试系统的基础上,进行改进,使得跟随电压真正跟随到OV;然后采用多路电子开关等手段,使得测试线路实现了自适应多量程的测试。试验结果表明,系统能真正获取开路电压与短路电流,并且,能实现电压在0～50V,电流在0．7～5．6A之间的自适应测量,开路电压不一致性〈2．2％,短路电流不一致性〈3．2％,满足了单体太阳电池与小组件太阳电池的测量。     

Structural optimization of a Cu(In,Ga)Se2 thin film solar cell using numerical simulation and design of experiment techniques

The structural optimization for a thin film solar cell module based on Cu(In,Ga)Se₂ is investigated through numerical simulation and sequential statistical analyses. First, an equivalent numerical model for solar cells is constructed with an electrical circuit consisting of large area diodes and analysis using finite element analysis (FEA). A good agreement in performance characteristic curves between the developed numerical model and practical solar cells is obtained after performing parameter adjustments. To maximize the light conversion efficiency, an optimization technique using the design of experiment (DOE) of orthogonal arrays is employed. The programmed block diagram is used to calculate electric potentials inside solar cell layers and the associated solar performances. Statistical analysis of variance (ANOVA) and F-test are used to discover the dominant design variables (DVs) which are more important on solar cell performances. The second order regression model which relates dominant DVs with solar cell efficiency is mathematically obtained by the employment of response surface model (RSM) and graphically described by the equipotential contour plots.     

Detection limits for glow discharge mass spectrometry (GDMS) analyses of impurities in solar cell silicon

The measurement of both doping elements and trace elements in solar cell silicon plays a key role for achieving high conversion efficiency of the solar cell device. Doping element concentrations in the range of few hundreds part per billions (ppb) and trace elements in the ppb or sub-ppb concentration range are typically present in multicrystalline silicon wafers for solar cells. Accurate and reliable measurements of these small amounts are not straightforward. The present work describes a fast-flow direct-current high resolution glow discharge mass spectrometer (GDMS). Detection limits for a number of impurities (B, Al, P, Ca, Ti, V, Cr, Mn, Fe, Ni, Co, Cu, Mo, Sn, W and Pb) of interest for solar cell applications have been investigated by GDMS. These detection limits are approximately 1 ppba or below, except for B, Al, P, Ca and Pb. All concentrations reported are quantitative since calculated relative sensitivity factors (RSF‘s) for Si matrix have been used. The detection limits have been achieved with minimum sample preparation and short analysis time.     

State-of-the-art Architectures and Technologies of High-Efficiency Solar Cells Based on III–V Heterostructures for Space and Terrestrial Applications

Multi-junction solar cells based on III–V compounds are the most efficient converters of solar energy to electricity and are widely used in space solar arrays and terrestrial photovoltaic modules with sunlight concentrators. All modern high-efficiency III–V solar cells are based on the long-developed triple-junction III–V GaInP/GaInAs/Ge heterostructure and have an almost limiting efficiency for a given architecture — 30 and 41.6% for space and terrestrial concentrated radiations, respectively. Currently, an increase in efficiency is achieved by converting from the 3-junction to the more efficient 4-, 5-, and even 6-junction III–V architectures: growth technologies and methods of post-growth treatment of structures have been developed, new materials with optimal bandgaps have been designed, and crystallographic parameters have been improved. In this review, we consider recent achievements and prospects for the main directions of research and improvement of architectures, technologies, and materials used in laboratories to develop solar cells with the best conversion efficiency: 35.8% for space, 38.8% for terrestrial, and 46.1% for concentrated sunlight. It is supposed that by 2020, the efficiency will approach 40% for direct space radiation and 50% for concentrated terrestrial solar radiation. This review considers the architecture and technologies of solar cells with record-breaking efficiency for terrestrial and space applications. It should be noted that in terrestrial power plants, the use of III–V SCs is economically advantageous in systems with sunlight concentrators.     

基于DSP的新型太阳方位跟踪系统

为了提高太阳方位跟踪精度,降低光伏发电系统的成本,利用光伏电池旋转产生的短路电流是交变电流的这一特点,通过离散傅里叶变换（DFT）求解交变电流的初相位,计算太阳的高度角和方位角,实现了对太阳方位的自动跟踪。并依此方法设计出了一套基于数字信号处理器（DSP）的新型太阳方位跟踪系统。实验结果表明,该系统能实现太阳光大范围内检测,并迅速跟踪,可避免多块光敏元件的不一致性所带来的问题,有效地提高了跟踪系统的精确性,可望在太阳能光伏发电工程中得到应用。     

Microelectrical characterizations of junctions in solar cell devices by scanning Kelvin probe force microscopy

Scanning Kelvin probe force microscopy was applied to the microelectrical characterizations of junctions in solar cell devices. Surface Fermi-level pinning effects on the surface potential measurement were avoided by applying a bias voltage (V_b) to the device and taking the V_b-induced potential and electric field changes. Two characterizations are presented: the first is a direct measurement of Bi-induced junction shift in GaInNAs(Bi) cells; the second is a junction-uniformity measurement in a-Si:H devices. In the first characterization, using Bi as a surfactant during the molecular beam epitaxy growth of GaInNAs(Bi) makes the epitaxial layer smoother. However, the electrical potential measurement exhibits a clear Bi-induced junction shift to the back side of the absorber layer, which results in significant device degradation. In the second characterization, the potential measurement reveals highly non-uniform electric field distributions across the n–i–p junction of a-Si:H devices; the electric field concentrates much more at both n/i and i/p interfaces than in the middle of the i-layer. This non-uniform electric field is due possibly to high defect concentrations at the interfaces. The potential measurements further showed a significant improvement in the electric field uniformity by depositing buffer layers at the interfaces, and this indeed improved the device performance.     

Instrumentation for accelerated life tests of concentrator solar cells

Concentrator photovoltaic is an emergent technology that may be a good economical and efficient alternative for the generation of electricity at a competitive cost. However, the reliability of these new solar cells and systems is still an open issue due to the high-irradiation level they are subjected to as well as the electrical and thermal stresses that they are expected to endure. To evaluate the reliability in a short period of time, accelerated aging tests are essential. Thermal aging tests for concentrator photovoltaic solar cells and systems under illumination are not available because no technical solution to the problem of reaching the working concentration inside a climatic chamber has been available. This work presents an automatic instrumentation system that overcomes the aforementioned limitation. Working conditions have been simulated by forward biasing the solar cells to the current they would handle at the working concentration (in this case, 700 and 1050 times the irradiance at one standard sun). The instrumentation system has been deployed for more than 10?000 h in a thermal aging test for III-V concentrator solar cells, in which the generated power evolution at different temperatures has been monitored. As a result of this test, the acceleration factor has been calculated, thus allowing for the degradation evolution at any temperature in addition to normal working conditions to be obtained.     

1/f噪声的精确测量及其在太阳能电池可靠性筛选中的应用

为了实现对太阳能电池可靠性的筛选分类,建立了一套低频噪声自动测试系统.首先,根据太阳能电池1/f噪声的来源,确定了在大电流密度情况下以1/f噪声功率谱作为太阳能电池可靠性指示的可行性.然后,由测试得到的功率谱曲线明确了通过比较在f为1 Hz频点处的1/f噪声功率谱值大小可以区分太阳能电池的可靠性.最后,根据半导体器件可靠性试验验证的分类标准,给出了确定筛选阈值的方法.实验结果表明:该方法可以在短时间内无损地完成一批太阳能电池3个等级的可靠性分类,平均每个太阳能电池的测试时间只需5 min.采用该筛选方法,能精确检测单一器件,解决了传统方法花费大、周期长,易引起器件的损伤,且只能得到一批器件可靠性的统计规律的问题.该方法适用于对太阳能电池可靠性要求高的应用场合.     

Evaluation of electrical contact area between metal and semiconductor using photo-induced current

Photo-induced current (PIC) is produced from excited electrons and holes in a semiconductor by irradiation of laser light. Since the intensity of the PIC depends on the traveling distance of carriers, measuring current between a metal and a semiconductor can be utilized for analyzing electrical contact. The spatial resolution of the PIC depends on the attenuated length and the thickness of the semiconductor, and its intensity is proportional to the contact pressure. By scanning laser light, we obtained two-dimensional distribution maps of electrical contacts between solids.     

Changes in the microstructural and electrical behavior of poly-Si films subjected to ion implantation and annealing process modifications

Polycrystalline silicon (poly-Si) films implanted with arsenic using beam currents of 500 μA (400°C) and 230 μA (room temperature) have been investigated via transmission electron microscopy (TEM), secondary ion mass spectrometry (SIMS), and spreading resistance analysis (SRA). Experimental observations demonstrated the annealed high beam current-implanted poly-Si to possess inferior electrical properties compared with that implanted at a lower beam current. The reduced electrical activity of the high beam current-versus the low beam current-implanted poly-Si was directly related to the postimplant microstructure (small grains ～140 nmvs. amorphous) and the mechanism of the subsequent anneal (grain growth vs. recrystallization). The recrystallization mechanism augmented the electrical activation of the As dopant (decreased sheet resistivity) via a reduction of total grain boundary area. Further improvement in the electrical performance of the low beam current-implanted poly-Si, a resistivity decrease of up to 28%, was incurred via a two-step annealing process. This process induced grain growth, which in turn minimized total grain boundary area and dopant trapping.     

A study on soldering characteristics of laser tabbing system for crystalline silicon photovoltaic module production

The most significant task in the solar cell industry today is to minimize the cost of solar cell development, thereby establishing grid parity early. One way to achieve this goal is to reduce the thickness of silicon solar cell, which would subsequently result in reduction in raw silicon material costs. The most commonly used tabbing process in solar cell production today is the heating bar process. This process utilizes electric heating bars to heat the ribbons on solar cells. In this study, a laser tabbing machine was developed to overcome the problems of tabbing process of heating bar technique for a thin crystalline silicon solar cell. An electric test and peeling test were executed on soldering ribbon on solar cells. The results indicate that the bonding force of ribbon does not affect electrical output of the solar cell. The electric power of soldered solar cell was decreased around 5% in output as compared to the original unsoldered solar cell. The electric powers of the laser soldered module and the heating-bar soldered module were very close. The decline in efficiency of both modules was about 1.13%. As a result of this study, it was confirmed that the laser tabbing system developed in this research can be applied in module manufacturing processes.     

V型耦合式刀片低能束流位置探测器及其性能检测

基于合肥国家同步辐射实验室(NSRL)低能量真空紫外光源的特点,研制了耦合式刀片低能束流位置探测器,用于在线监测波荡器辐射出的低能量真空紫外相干光源的稳定性.探测器采用V型耦合式刀片作为探针,基于错位安装、倾斜嵌入被测光束边缘和直流偏压捕集自由电子等技术有效增强光电效应,提高探针的响应灵敏度和探测器监测精度.介绍了耦合式刀片低能束流位置探测器的结构特点、探测原理和性能测试,在线监测了NSRL波荡器光源的稳定性,获得了一系列有价值的试验数据.结果表明:该探测器能完成NSRL-0.8GeV低能储存环上插入件光源的在线监测,满足对改造后的新光源各插入件辐射光束位置稳定监测的要求.