TS-Space Systems is proud to have supplied a Unisim Solar Simulator to NEC Space Technologies, LTD. a world leader in the manufacture and testing of satellite equipment.

The Unisim close match solar simulator provides a world leading close spectral match to the standard AM0 spectrum via multiple discrete wavebands which is vital for accurately characterising the multijunction solar cells used for space applications.

"We are very pleased to work with NEC Space Technologies LTD again", said Dr Bill Williams, Director at TS-Space Systems, "We are proud to add NEC Space Technologies LTD. to the long list of leading PV research and manufacturing groups who have selected our solar simulators for their work".

We are busy finishing several large simulator builds at the moment, but we are still planning new additions to our products and services for 2016.

We have new LED boost options for our Unisim Compact solar simulators and we will be launching our in-house simulator demo service in 2016. Customers will be able to book a day on our in-house Unisim Compact solar simulator and try it out for themselves. Tea and biscuits included!

2015 has been an incredibly busy year for our outgassing rig. If you are interested in outgassing or any of our in-house test services, the sooner you contact us the more likely we are to fit you in to our test schedule.

We value product support very highly at TS-Space Systems which is why we offer extensive support via phone and email for the full lifetime of every TS-Space Systems product. Training is also provided at our premises where customers can take advantage of one-on-one tuition with the product designers to learn how to operate and maintain their solar simulators and other tools.

Xenon Arc Lamps - These have been commonly used in most simulators since the very first 1960's designs due to the raw output having a fairly approximate match to the AM0 spectrum. There are, however, large infra-red "spikes" which must be attenuated to achieve a close spectral match. Even so, a single source solar simulator consisting of an IR filtered xenon arc source will provide a crude match to AM0/AM1.5, which is acceptable if you are testing single-junction devices or biological tests where an exact spectral match is not necessary. They are expensive compared to other arc sources, primarily due to the increasing demand for a limited global supply of xenon.

Metal Halide Arc Lamps (HMI) - Commonly used in film and television lighting where a close match to daylight is required along with a high temporal stability for filming, metal halide arc lamps provide an alternative to xenon which are more stable, give better temporal stability, are low-pressure, easier to maintain and cheaper. The spectral perturbations in the infra-red are much reduced from xenon, meaning they are excellent basis for both Class "A" and advanced solar simulators (see relevant section above). For reference, an unfiltered metal halide arc lamp will produce a B class spectral match.

Quartz Tungsten Halogen Lamps (QTH) - These provide an excellent black-body match in the infra-red but very poor across the visible range. As such they are more commonly used in more advanced multi-source solar simulators. See our previous post for more information on advanced solar simulators.

The basic technique, assuming that illumination levels above and below AM0 are required, is to reduce the overall level of illumination of the simulator so as to be, say, 10% below AM0, but maintaining the AM0 spectral distribution (Figure 1).

Selected LED's are then used to provide the correct illumination for each junction at AM0 (Figure 2). By varying the output of these LED's, the current in any selected junction may be increased or decreased as required. In this way, any junction may be investigated independently of any other junction. Please note that alternative LED wavelengths to the ones demonstrated here are available.

The importance of a good spectral match or 'close-match' solar simulator for accurately measuring and investigating multi-junction solar cells was clear and has since been thoroughly demonstrated in the research literature:

"The photovoltaic characterization of triple-junction InGaP2/GaAs/Ge solar cells is presented. Measurements made using a single light source solar simulator are compared with other measurements made using a multi-light source solar simulator that provides a close match to the air mass zero (AM0) solar spectrum. The output spectrum of the solar simulators has been measured, and two methods for calibrating the simulator output intensity haven been employed. The spectral response of the solar cells has been characterized through quantum efficiency measurements. These data are analyzed to determine the effect of the simulator spectrum on the measured photovoltaic response, and in particular, areas where spectral mismatch between the simulator and AM0 can lead to inaccurate performance predictions are highlighted."[3]

At TS-Space Systems, when we made the worlds first multi-source close match solar simulator back in 1997 [2], we also made the world's first multi zone solar simulator by definition. What is a "zone" when it comes to solar simulators? It's a good question and one we get asked quite a lot of the time.

Modern multi-source solar simulators follow a general pattern of combining an arc lamp (traditionally Xenon) with one or more  incandescent lamps. At TS-Space Systems we've lead the way by adopting Metal Halide arc lamps for our latest range of solar simulators which are cheaper and much more stable than Xenon sources without using feedback controllers.

But where our solar simulators really excel is their division of the spectrum into independently controllable wavebands. We call these spectral "zones". As an example, the measured spectrum of a TS-Space Systems Unisim, quad-source (four zone) solar simulator is shown to the left.

The intensity of each "zone" can be adjusted independently in a TS-Space Systems Unisim solar simulator. Being able to adjust discrete portions of the spectrum while a device is under test allows for specific sub-cells to be limited or saturated with their appropriate wavelength of light. Thus the behaviour and characteristcs of the device can be fully investigated.

A further distincition can therefore be drawn between advanced solar simulators which provide a close-match and those which not only provide a close-match, but divide the spectrum into controllable "zones" which are suited to the spectral response of each band gap within the solar cell. 

What happens when you need more than four "zones"? That's where our Unisim N-Zone comes in.

For the uninitiated, when selecting a solar simulator, there seems to be a huge number of manufacturers and models available. While there are standards in place that require simulators to be classified according to their performance, these have not kept pace with the advances of solar simulator technology or the devices they are used to test. Our guide to solar simulators attempts to list the basic terminology and elements of solar simulators, how they are classified by the existing standards and, finally, how advanced solar simulators differ and the advantages they provide. It is in no way a complete work, but is intended to help those who are new to the field by giving them a good entry-level knowledge of the subject.

We recommend downloading and reading the international standards (listed under 'Standards' here) to assist with the terminology and concepts described throughout this site.

If you have a suggestion for additional content you'd like to see here, or if you have questions, please feel free to contact us. We would like to hear from you.