Testing solar cells

Each cell should be tested for voltage and current output before you solder the tab ribbon to the cells. Even if you are using up-to-spec new cells, test them before you solder. They might still be flawed or have been damaged in transit and handling. 

Solar cell manufacturers use an array of lights that closely mimic solar output to test cells. This gives excellent results, but is expensive and not really necessary. 

The most low cost test option is simply to take the cells outdoors on a very sunny day with a multimeter. The good news is that the sunlight testing station is free. The bad news is that if it is not a perfectly clear day, barely perceptible changes in light intensity occur within seconds due to a variety of atmospheric changes. This can easily throw your readings off a 

With the multimeter, measure the open circuit voltage and short circuit current for each cell. Write down the reading for each one. The cells do not have to exactly match each other in voltage and current output. The point is to match the cells so that all of the cells put out voltage and current at or above what your target output is. The lowest single cell output will limit all the others to its output level, so try to match them as closely as possible. 

When I was testing the cells for this project, I waited for the first sunny day to get out and test the cells. I tested and selected my cells, and connected them together in a string, The next day, when I performed the second test, I was surprised to find that my current readings were much higher than I had expected. What I thought was a very sunny day for the first test was not as sunny as the day of the second test. I realized that there must have been more particulates and or moisture in the air on the first test day than on the second test day. 

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In addition, other utiUties are installing estabUshed solar cells in a growing number of tests that may lead to a mass market. The studies may indicate the extent to which solar cells can be used to avoid installation costs for new distribution lines between conventional power plants and remote customers buildings. Also, among other objectives, PV cells may provide an economical means of helping to supply demand during peak summer periods in northern climates. 

Peter and Wang [266] invented a channel flow cell for rapid growth of CdTe films they showed that 2 p,m Aims can be deposited in less than 20 min, as opposed to the 2-3 h normally required in the conventional stirred single batch cells. The as-deposited films were structurally more disordered than the conventional ones, but after annealing and type conversion they became suitable for fabrication of efficient solar cells. A test cell with an AMI.5 efficiency approaching 6% was fabricated using a film prepared in the channel cell. 

Table II shows, as an example, the combinations of low and high levels for three factors selected by a design team for an accelerated test Involving photovoltaic solar cells. In column 2 the three factors are seen to be temperature T (50 C, 95 C), relative humidity RH (60%, 85%), and ultraviolet radiation UV (five suns, 15 suns). The eight combinations of the high and low levels are shown, together with the predicted months to failure for each combination. In this example the documentation to support each prediction is symbolically referenced as shown in the last column. The documentation includes assumptions, calculations, references to the literature, laboratory data, computer simulation results, and other related material. Such a factorial table is first completed by each scientist independently. Subsequently, the team alms to generate a single consensus factorial table has the same form as that shown in Table II.

Thomas, R. E. Gaines, B. G. "Methodology for Designing Accelerated Aging Tests for Predicting Life of Photovoltaic Arrays" Department of Energy/National Bureau of Standards Workshop on Stability of Thin Film Solar Cells and Materials, Washington, D.C., May 1-3, 1978. 

FABRICATION AND TESTING OF CIS SOLAR CELLS 6.5.1 Cell Fabrication at GRC... 

Figure 17.15 Photocurrent-voltage characteristics of dye-sensitized solar cells in the presence of various nanocomposite gel electrolytes. The inset shows the viscous MWCNT gel at the bottom of a test tube. Reprinted from Ref. 51. Copyright 2004 with permission from Elsevier.

Cyanine and merocyanine dyes have also been tested as dye photosensitizers [132-137]. A nanocrystalline 2 solar cell sensitized by the special merocyanine dye as shown in Fig. 15 revealed a good efficiency of 4.2-4.5% (7 =... 

Table 4 Test of Long-Term Stability of Dye-Sensitized Ti02 Solar Cells Conducted at Various Institutions... 

Building and testing efficiency of solar cells Earth observations and satellite imaging... 

The morphological problems associated with the BHJ solar cells, such as low concentration of percolating pathways which are needed in order to bring the separated charge carriers to their corresponding electrodes, have prompted the utilization of molecules in with the donor and the acceptor moieties were covalently linked. In this connection several examples of Pc-based polymers [161,162], Pc-C6o dyads [85,87,88] and triads [275] have been prepared and tested for photovoltaic applications, but the efficiencies of these systems have been proved to be still low. 

Liu prepared a sandwich type coordination compound (103) from porphyrin and phthalocyanine with the assistance of a microwave. The resulted compounds showed good solubility in conventional organic solvents. The photoelectric conversion properties have been tested with a Gratzel type cell. The results revealed that the sandwich type compound showed better photo-electric conversion efficiency than the corresponding monomeric porphyrin or phthalocyanine precursors. The short-circuit photocurrent of the solar cell with this sandwich type compound as sensitizer, was, as high as 691.31 A cm-2, which was much better, than those of porphyrin or phthalocyanine monomers [100]. 

Finally, as it is not possible to experimentally test all the various kinds of surface textures within actual solar cell configurations, it can be useful to use numerical simulations, in order to evaluate the best combination of surface textures and roughness for both front and back TOO layers. The method usually applied for such simulations is to take the main optical properties of each layer of the solar cell (absorption, thickness, haze factor, ADF, surface roughness,. ..), and then to put them all together in order to compute the quantum efficiency curve of the resulting solar cell. Such a task of optically simulating solar cells is very complex and beyond the scope of the present chapter. However, it is important to note here that a numerical simulation is always only an imperfect tool and can in no way fully replace experimental work and measurements on actual solar cells. 

Gordon et al. [59] proposed a figure of merit defined by the ratio of the electrical conductivity over the optical absorption coefficient in the visible spectral range. They tested many dopants for AP-CVD ZnO films, and obtained the highest figure of merit for fluorine-doped ZnO, which they used as TCO for amorphous silicon solar cells. 

Reliable stability data of the p-i-n solar cell itself are not easily obtained, especially for non-encapsulated cells or modules. One of these tests e.g. for EN/IEC 61646 certification of modules is the so-called damp-heat test (85°C, 85% humidity, up to lOOOh). Recent studies were performed by Stiebig et al. [50, 51] exposing different types of cells to harsh conditions. One of the most important results was the excellent stability of silicon thin film solar cells. Remarkably, this is also valid for small area modules even without encapsulation [52]. This is of high interest because costs and efforts for module encapsulation strongly depend on the inherent stability of the solar cells. As a more detailed treatment of this subject is beyond the scope of this chapter, the reader is referred to the original papers [50,51]. 

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