标签: 光伏电池

德国科学家发明了可利用太阳能给手机充电的半透明有色太阳镜镜片，镜片的有机太阳能电池有一个微处理器和两个电量显示器，显示太阳光照强度以及周围环境温度，镜片甚至还可以利用太阳能给手机充电。研究人员表示，该技术或许为太阳能的进一步应用奠定基础，例如将有机太阳能电池嵌入窗户或玻璃天窗。 有机太阳能电池可以利用太阳能发电，其特点是透明，重量轻，并且可以制作成不同的颜色和形状。它在更加广泛的领域里可以取代传统的较重，且硬度更大的硅太阳能电池。 德国卡尔斯鲁厄理工学院研究人员将这种太阳镜作为样本来展示有机太阳能电池的应用。该学院光学技术有机太阳光电小组负责人亚历山大.克斯曼博士说：“我们用这种太阳能技术来填补其他太阳能技术的空缺”。这种智能太阳能眼镜可以自我负能，从而测量和显示太阳光强度以及温度，在室内照明度低至500勒克斯的条件下(一般办公室或居住环境照明度)也同样工作。即使在室内，两个镜片也可以分别产生200微瓦特的电量，这足以给如助听器或计步器充电，镜片厚度为1.6毫米，重量为6克，和普通的镜片没有差别，因此也具有商业价值。微处理器和显示器嵌装在眼镜的太阳穴位置，以柱状图的方式显示光照强度和周围环境温度。 一名协助开发太阳能眼镜的博士在读生多米尼克.兰德尔称：“我们研发的太阳能眼镜是为了表明有机太阳能电池在传统的光伏电池所不能应用的领域是如何工作的”，它机械灵活，可根据不同具体要求而制定出相应的颜色、透明度、形状以及大小，有机太阳能电池也因此变得备受关注。 克斯曼教授还透露，太阳能电池的另一项应用是要将其融入建筑中。由于玻璃高层建筑的正面通常需要遮蔽，如何利用有机太阳能电池将光能转化为电能，这是研究人员所面临的问题。美国麻省理工学院研究人员正在为此作出努力，2013年，麻省理工学院微系统技术实验室研究团队宣称他们正在发明一种可以将窗户或电子产品转化为发电机的透明太阳能电池。对在能源系统材料研究中心进行有机太阳能电池和半导体元器件基础研究的工程师们来说，未来要做的是利用卷对卷技术给大型物体表面覆盖上有机太阳能电池。

  与I-V测量类似，电容测量 也用于太阳能电池的特征分析。根据所需测量的电池参数，我们可以测出电容与直流电压、频率、时间或交流电压的关系。例如，测量PV电池的电容与电压的关系有助于我们研究电池的掺杂浓度或者半导体结的内建电压。电容-频率扫描则能够为我们寻找PV衬底耗尽区中的电荷陷阱提供信息。电池的电容与器件的面积直接相关，因此对测量而言具有较大面积的器件将具有较大的电容。 Like I‑V measurements, capacitance measurements can serve to characterize a solar cell. The capacitance can be measured as a function of the DC voltage, frequency, time, or AC voltage, depending on what parameters of a cell need to be determined. For example, measuring the capacitance of a PV cell as a function of voltage can help when studying the doping concentration of the cell or the built-in voltage of the junction. A capacitance-frequency sweep is useful to provide information on the finding of charge traps in the PV substrate’s depletion region. The capacitance of the cell is directly related to the area of the device, so that devices with large areas will present large capacitances to the measurement setup.   C-V测量测得的是待测电池的电容与所加载的直流电压的函数关系。与I-V测量一样，电容测量也采用四线技术以补偿引线电阻 。电池必须保持四线连接。测试配置应该包含带屏蔽的同轴线缆，其屏蔽层连接要尽可能靠近PV电池以最大限度减少线缆的误差。基于开路和短路测量的校正技术能够减少线缆电容对测量精度的影响。C-V测量可以在正偏也可以在反偏 情况下进行。反偏情况下电容与扫描电压的典型曲线（如图6所示）表明在向击穿电压扫描时电容会迅速增大。 C‑V measurements require that the capacitance of the cell be measured as a function of an applied DC voltage. Like I-V measurements, the capacitance measurements are made using a four-wire technique to compensate for lead resistance. The four-wire connections should be maintained to the cell. The test setup should include shielded coaxial cables, with the shields connected as close as possible to the PV cell to minimize errors from the cables. Calibration techniques based on measuring open and short circuits will reduce the effects of cable capacitance on measurement accuracy. C‑V measurements can be made under either forward- or reverse-biased conditions. A typical plot of capacitance versus swept voltage under reverse-biased conditions ( Fig. 6 ) shows how capacitance increases rapidly towards a breakdown voltage.                 图6. PV电池电容与电压关系的典型曲线。 Fig 6. This is a typical plot of capacitance versus voltage for a PV cell.   另外一种基于电容的测量是激励电平电容压型（DLCP），可在某些薄膜太阳能电池（例如CIGS）上用于判断PV电池缺陷密度与深度的关系。这种测量要加载一个扫描峰-峰交流电压并改变直流电压，同时进行电容测量 。必须调整这两种电压使得即使在扫描交流电压时也保持总加载电压（交流+直流）不变。通过这种方式，材料内部一定区域中暴露的电荷密度将保持不变，我们就可以得到缺陷密度与距离的函数关系。 2 Another capacitance-based measurement, drive level capacitance profiling (DLCP), can be used to determine the defect density of a PV cell as a function of depth on some thin-film solar cells such as CIGS. The measurement involves applying a swept peak-to-peak AC voltage and varying the DC voltage while making capacitance measurements. The two voltages must be adjusted in such a way that the total applied voltage (AC + DC) remains constant even as the AC voltage is swept. By doing this, the exposed charge density within the material will remain constant for a given location, making it possible to determine the defect density as a function of distance. 如何使用库仑计测量弱电流及优点？http://www.keithley.com.cn/llm/a/15.html 源电阻和源电容如何影响灵敏的电流测量工作？http://www.keithley.com.cn/llm/a/7.html 内部的偏置电压和零点飘移减小的解决办法http://www.keithley.com.cn/llm/a/31.html 吉时利扩展DC源测量仪器的量程兼容ACS基础版软件http://www.keithley.com.cn/news/prod090827 J.T. Heath, J.D.Cohen, and W.N. Shafarman, "Bulk and metastable defects in CuIn1-XGaXSe2 thin films using drive-level capacitance profiling," J.Appl. Phys . 95, 1000 (2004).

其它一些可以从PV电池直流I-V曲线中得出的数据表征了它的总体效率——将光能转换为电能的好快程度——可以用一些参数来定义，包括它的能量转换效率、最大功率性能和填充因数。最大功率点是最大电池电流和电压的乘积，这个位置的电池输出功率是最大的。   Other data that can be derived from the DC I-V plot of a PV cell characterize its overall efficiency—how well it transforms light into electricity—and can be defined by a number of parameters, including its energy conversion efficiency, its maximum power capability, and its fill factor. The maximum power point is the product of the maximum cell current and voltage where the power output of the cell is greatest.   填充因数 （FF）是将PV电池的I-V特性与理想电池I-V特性进行比较的一种方式。理想情况下，它应该等于1，但在实际的PV电池中，它一般是小于1的。它实际上等于太阳能电池产生的最大功率（P MAX =I MAX V MAX ）除以理想PV电池产生的功率。填充因数定义如下：   The fill factor (FF) is a way to compare a PV cell’s I‑V characteristics to those of an ideal cell. Ideally, it would have a value of one, but in practical PV cells, it is always less than one. It is essentially the maximum power produced by a solar cell (P MAX =I MAX V MAX ) divided by the power produced by an ideal PV cell. The fill factor is defined as:     FF = I MAX V MAX /(I SC V OC )   其中I MAX =最大输出功率时的电流，V MAX =最大输出功率时的电压，I SC =短路电流，V OC =开路电压。 where I MAX = the current at the maximum power output, V MAX = the voltage at the maximum power output, I SC = the short-circuit current, and V OC = the open-circuit voltage.     转换效率（h）是光伏电池最大输出功率（P MAX ）与输入功率（P IN ）的比值，即： The conversion efficiency (h) is the ratio of the maximum power output (P MAX ) to the power input (P IN ) to the photovoltaic cell, or     h = P MAX /P IN   PV电池的I-V测量 可以在正偏（光照下）或反偏（黑暗中）两种情况下进行。正偏测量 是在PV电池照明受控的情况下进行的，光照能量表示电池的输入功率。用一段加载电压扫描电池，并测量电池产生的电流。一般情况下，加载到PV电池上的电压可以从0V到该电池的开路电压（V OC ）进行扫描。在0V下，电流应该等于短路电流（I SC ）。当电压为V OC 时，电流应该为零。在如图1所示的模型中，I SC 近似等于负载电流（I L ）。   I‑V measurements of a PV cell can be performed under forward-biased (in the light) or reverse-biased (in the dark) conditions. Forward bias measurements are performed under controlled illumination of the PV cell, with the light energy representing the input power to the cell. The cell is also swept through a range of applied voltages, and the resulting current from the cell is measured. Typically, the voltage applied to the PV cell might be swept from 0 V to the open-circuit voltage (V OC ) for that cell. At 0 V, the current is expected to equal the value of the short-circuit current (I SC ). When the voltage is set at V OC , the current is expected to be zero. In the model of Fig. 1 , I SC is approximately equal to the load current (I L ).       PV电池的串联电阻（r s ）可以从至少两条在不同光强下测量的正偏I-V曲线中得出。光强的大小并不重要，因为它是电压变化与电流变化的比值，即曲线的斜率，就一切情况而论这才是有意义的。记住，曲线的斜率从开始到最后变化很大，我们所关心的数据出现在曲线的远正偏区域（far-forward region），这时曲线开始表现出线性特征。在这一点，电流变化的倒数与电压的函数关系就得出串联电阻的值：   The series resistance of a PV cell (r s ) can be determined from at least two forward-biased I‑V curves, measured at different light intensities. The magnitudes of the light intensities are not important, because it is the change in voltage with the change of current, or slope of the curve, that is meaningful in all cases. Bearing in mind that the slope of the curve changes dramatically from beginning to end, meaningful data can be found at the curve’s far-forward region, where the curve starts to take on linear characteristics. The inverse of the change in current as a function of voltage at this point gives the value for the series resistance:   r s = ΔV/ΔI   到目前为止本文所讨论的测量都是对暴露在发光输出功率下，即处于正偏条件下的PV电池进行的测量。但是PV器件的某些特征，例如分流电阻（r sh ）和漏电流，恰恰是在PV电池避光即工作在反偏情况下得到的。对于这些I-V曲线，测量是在暗室中进行的，从起始电压为0V到PV电池开始击穿的点，测量输出电流并绘制其与加载电压的关系曲线。利用PV电池反偏I-V曲线的斜率也可以得到分流电阻的大小（如图5所示）。从该曲线的线性区，可以按下列公式计算出分流电阻：   The measurements discussed so far have been made with a PV cell exposed to light-generating output power, under forward-biased conditions. But some of the characteristics of a PV device, such as the shunt resistance (r sh ) and the leakage current, are best found with the PV cell shielded from light and operating under reverse-biased conditions. For these I‑V plots, measurements are made in a dark enclosure, from a starting voltage of 0 V to a point at which the PV cell begins to break down, with the output current measured and plotted as a function of the applied voltage. The shunt resistance can also be found by using the slope of a PV cell’s reverse bias I‑V curve ( Fig. 5 ). From the linear region of the curve, the shunt resistance can be found from   r sh = ΔV Reverse Bias /ΔI Reverse Bias                          V 反偏                                    用于估算r sh 的线性区                                          ΔI 反偏 ΔV 反偏       log I 反偏     图5. 利用PV电池反偏I-V曲线的斜率可以得到PV电池的分流电阻。   Fig 5. A PV cell’s shunt resistance can be found by using the slope of a PV cell’s reverse bias I‑V curve.   除了在没有任何光源的情况下进行这些测量之外，我们还应该对PV电池进行正确地屏蔽，并在测试配置中使用低噪声线缆。   In addition to making these measurements in the absence of any light sources, the PV cell should also be properly shielded and low-noise cables used in the test setup.           吉时利太阳能电池（光电）的电特性和测量http://www.keithley.com.cn/solar_cell EP/238:Learn the Secret to Solar Cell (Photovoltaic) Test. Get our new solar cell information kit today! http://www.keithley.com.cn/promo/ep/238 吉时利太阳能电池（光电）的电特性和测量http://www.keithley.com.cn/solar_cell

PV电池 的等效电路模型（如图1所示）能够帮助我们深入了解这种器件的工作原理。理想PV电池的模型可以表示为一个感光电流源并联一个二极管。光源中的光子被太阳能电池材料吸收。如果光子的能量高于电池材料的能带，那么电子就被激发到导带中。如果将一个外部负载连接到PV电池的输出端，那么就会产生电流。 The equivalent-circuit model for a PV cell ( Fig. 1 ) provides some insight into the operation of the device. An ideal PV cell can be modeled as a light-induced current source in parallel with a diode. Photons in a light source are absorbed into the solar cell materials. If the photon energy is greater than the bandgap of the cell material, then electrons are excited into the conduction band. If an external load is connected across the output terminals of the PV cell, current will flow.                                      图1. 由一个串联电阻（R S ）和一个分流电阻（r sh ）和一个光驱电流源构成的光伏电池等效电路。 Fig. 1. The equivalent circuit of a photovoltaic cell shows a series resistance (R S ) and a shunt resistance (r sh ), along with a light-driven current source. 由于电池衬底材料及其金属导线和接触点中存在材料缺陷和欧姆损耗，PV电池模型必须分别用串联电阻（R S ）和分流电阻（r sh ）表示这些损耗。串联电阻是一个关键参数，因为它限制了PV电池的最大可用功率（P MAX ）和短路电流（I SC ）。   Because of material defects and ohmic losses in the cell substrate material as well as in its metal conductors and contacts, the PV cell model must also include series resistance (r S ) and shunt resistance (r sh ) respectively, to account for these losses. The series resistance is a key parameter because it limits the maximum available power (P MAX ) and the short-circuit current (I SC ) of the PV cell. PV电池的串联电阻（r s ）与电池上的金属触点电阻、电池前表面的欧姆损耗、杂志浓度和结深有关。在理想情况下，串联电阻应该为零。分流电阻表示由于沿电池边缘的表面漏流 或晶格缺陷造成的损耗。在理想情况下，分流电阻应该为无穷大。 The series resistance (r s ) of the PV cell may be due to the resistance of the metal contacts on the cell, ohmic losses in the front surface of the cell, impurity concentrations, or junction depth. Under ideal conditions, the series resistance would be zero ohms. The shunt resistance represents the loss due to surface leakage along the edge of the cell or due to crystal defects. Under ideal conditions, it would have an infinite value. 要提取光伏电池的重要测试参数，需要进行各种电气测量 工作。这些测量通常包含直流电流和电压、电容以及脉冲I-V 。 To extract important test parameters about the solar cell, a variety of electrical measurements can be performed. These measurements often include DC current and voltage, capacitance, and pulsed I-V.   Pv电池http://www.keithley.com.cn/news/searchresults?cx=012699874533381273845%3Ayqrfisritgocof=FORID%3A11%3BNB%3A1ie=UTF-8q=PV%E7%94%B5%E6%B1%A0sa.x=11sa.y=11 表面漏流：纳米科学研究实验室http://www.keithley.com.cn/re/nrl 电气测量：吉时利大学提供免费培训研讨会http://www.keithley.com.cn/news/prod020311 4200-PIV-Q脉冲I-V，具有静点和双通道脉冲http://www.keithley.com.cn/products/localizedproducts/semiconductor/4200pivq