EP1447615A2 - Pulsed sun simulator with improved homogeneity - Google Patents

Abstract

Sun simulator has a pulsed radiation source (1) for generation of electromagnetic radiation and at least a reflector (7) that reflects the radiation in the output direction (10). The reflector element is arranged at least partially adjoining the radiation source, is at least partially metallic and receives at least a part of the striking voltage applied to the radiation source.

Description

The present invention relates to a pulsed sun simulator, especially one Sun simulator used to measure solar cells like single-junction solar cells and multi-junction solar cells can be used.

Sun simulators are used to simulate the natural sunlight to the Effects of sunlight on certain objects to be irradiated too to be able to investigate under laboratory conditions. A special application is the investigation of the performance of solar cells.

Sun simulators are known for example from US 4,641,227. There will through a suitable arrangement and filtering of two independent radiation sources and a subsequent superposition of those from these radiation sources outgoing radiation a simulation of the sunlight is realized. As However, radiation sources are not used as pulsed radiation sources. Around these radiation sources are bundling parabolic mirrors with a distance like this arranged that the radiation sources are each in the focus of the parabolic mirror are located to focus the radiation in the direction of the target to be irradiated.

DE 201 03 645 describes a pulsed sun simulator with a displaceable Filters, the spectrum of a flash lamp by suitable, movable Filter is adapted to the spectrum of the sun.

EP 1 139 016 describes a pulsed sun simulator, in which with the aid of flat mirror elements spaced from a pulsed radiation source are arranged, usually parabolic, again the Radiation source is placed in focus, creating improved illumination of the target to be irradiated is to be guaranteed. The spectrum of The beam of rays reflected from the mirror elements can also be filtered be appropriately adapted to provide additional radiation to the target in one to achieve the desired wavelength range.

However, all of these possibilities from the prior art give no indication such as an improved homogeneity of the irradiation of the target to be irradiated can be achieved.

The object of the present invention is to provide an improved Sun simulator arrangement, in particular with improved homogeneity. This The object is achieved by the features of claim 1.

• eine gepulste Strahlungsquelle zur Erzeugung einer elektromagnetischen Strahlung,
• mindestens ein im Bereich der Strahlungsquelle angeordneten Spiegelelement, welches Anteile der Strahlung der Strahlungsquelle im wesentlichen in Richtung der Abstrahlrichtung des Sonnensimulators reflektiert. Das Spiegelelement kann dabei insbesondere senkrecht zur Abstrahlrichtung angeordnet sein.

Gemäß der Erfindung ist nun vorgesehen, dass

• das mindestens eine Spiegelelement unmittelbar an die Strahlungsquelle angrenzend angeordnet ist,
• das mindestens eine Spiegelelement zumindest teilweise metallisch ausgebildet ist und
• zumindest ein Teil der Zündspannung der gepulsten Strahlungsquelle an das Spiegelelement angelegt ist.

The sun simulator according to the invention has the following:

• a pulsed radiation source for generating electromagnetic radiation,
• at least one mirror element arranged in the region of the radiation source, which reflects portions of the radiation from the radiation source essentially in the direction of the radiation direction of the sun simulator. The mirror element can in particular be arranged perpendicular to the direction of radiation.

According to the invention it is now provided that

• the at least one mirror element is arranged directly adjacent to the radiation source,
• the at least one mirror element is at least partially metallic and
• at least part of the ignition voltage of the pulsed radiation source is applied to the mirror element.

In contrast to the prior art mentioned at the outset, the present invention, the mirror element is not from the radiation source spaced apart, but the mirror element lies directly on the Radiation source. In particular, a radiation source with a spectral width and / or a spectral intensity distribution used be largely the spectral width and / or the spectral Corresponds to the intensity distribution of the sunlight.

Now, as in the case of the present invention, the mirror element at least partially metallic, then a voltage can be applied to the Mirror element can be created. In particular, it can be a subassembly or a constructive sub-element of the mirror element such as, for example a frame, a bracket or the mirror surface partially or be completely metallic. The applied voltage supports the pulsed ignition of the radiation source and thereby helps to a more homogeneous Ignition of the radiation source. Usually used as radiation sources gas-filled tubes are used, on the above suitably arranged An ignition voltage is applied to electrodes. Alternative to one specifically for the ignition used ignition voltage or in addition to this ignition voltage can have a constant voltage at the ends of the gas-filled tube be created. With such radiation sources, one plants itself when ignited Luminous discharge from one electrode through the tube to the other electrode continued. This process leads to an inhomogeneous radiation effect. The additionally applying a voltage to that directly at the radiation source adjacent mirror element leads to a significantly faster and more homogeneous Ignition of the radiation source. Here is the immediate concern of the Mirror element at the radiation source crucial, because only then best possible effect when igniting and thus the best possible Homogeneity can be achieved.

In addition, the mirror element causes reflection of radiation components the radiation source, which is opposite to the desired radiation direction of the sun simulator are broadcast. On the one hand, this increases efficiency the radiation source increases, so it becomes less overall Energy needed. It can also reduce the radiation source Power operated, which means that the maximum of Radiation spectrum migrates into the infrared range. This is just one Desired and advantageous effect, as usual sun simulators in particular Infrared range is too low a radiation intensity compared to the sun spectrum respectively. Also due to the reflective effect of the mirror elements homogeneity in the direction of the radiation direction of the sun simulator the radiation advantageously improved.

A first development of the present invention provides that at least one mirror element is planar. This is precisely the reason a very homogeneous illumination of the target to be irradiated can be achieved.

Furthermore, it can be provided that the at least one mirror element, specifically the mirror surface of the mirror element, a material or a Has coating, which is designed such that the Reflective effect of the mirror element in the infrared range is significantly higher than in the UV range. In particular, this is a highly reflective material or a highly reflective coating, which or which in the Infrared range a reflection effect greater than 60%, preferably greater than 70%, ideally greater than 90%. Thus, also through the suitable choice of material or coating of the mirror element resulting spectrum can be influenced in the desired manner, namely towards an intensification of the intensity in the infrared range. In particular, can it should be provided that the at least one mirror element partially or is made entirely of gold or has a coating made of gold or a gold-containing alloy. But it can also be provided be that the at least one mirror element is a metal layer with a Has oxide layer, in particular a light metal, for example Aluminum. However, this metal layer can also be coated with a suitable one Coating can be coated as described above, the has the desired reflective effect. Alternatively, this can also be done Mirror element with a semiconductor layer, for example silicon Have oxide layer, the oxide layer also with another Coating, for example made of metal, in particular made of aluminum can be. The semiconductor oxide layer can in particular be used as a thermal Oxide layer can be formed, as in a thermal oxidation process is produced. This gives a practically single-crystal semiconductor oxide layer, which is a very precisely defined interface to the adjacent one Has semiconductor material. A metal layer can then be applied to the oxide layer for example by vapor deposition.

It turns out that metals such as gold as well as metals with oxide layers such as especially light metals and also semiconductors with oxide layers very much have good reflection properties, especially in the infrared range. Just these materials can therefore be advantageous in the context of the present invention be used.

A further improvement in the homogeneity of the radiation from the sun simulator can be achieved in that the radiation source in its longitudinal extent is curved. By a straight extension of the Radiation source, as provided for example in EP 1 139 016, can be a sufficient homogeneity cannot be achieved. In particular, be provided that the radiation source is annular or helical is trained.

The homogeneity of the radiation can be increased even further by that the radiation source is surrounded by a housing, which in Direction of radiation in the wall area several arranged one behind the other Has aperture elements. These aperture elements catch those radiation components the radiation source, which is not directly or not predominantly in Direction of the radiation direction are emitted. These aperture elements can preferably additionally with a low reflective coating coated or made of a low reflective material, to largely prevent stray radiation.

A preferred development of the invention provides that the radiation source and / or the mirror element via holders with a carrier plate made of granite. The surface of the carrier plate is either polished or microscopically roughened to reduce reflectivity exhibit. Such a granite slab has proven to be the ideal carrier slab proven to have a high stability, in particular also a high temperature stability has, on the other hand, the required stability and insulation effect against the high voltages that exist across the brackets and conductive leads at the radiation source and / or the at least apply a mirror element.

In particular, the radiation source can be designed as a xenon flash lamp his. Furthermore, as is generally known from DE 201 03 645, additional filtering means are provided to cover the spectrum of the sun simulator to influence still further in the desired manner. To do that in the Irradiation plane incident spectrum of the radiation vary even further To be able to provide that at least two filters in the are arranged essentially perpendicular to the direction of radiation, wherein the filters are designed such that they are either the same or suppress different portions of the radiation. This results in Overall spectrum now a superposition of the radiation components that are not a filter have passed the radiation components that have passed the first filter and the proportion of radiation that passes through the second filter or even more filters to have. If the filters are arranged so that they are pushed over one another radiation components also result first a first and then a second filter or even more filters have happened.

For a special use of the sun simulator for the measurement of Solar cells can be provided in an irradiation plane measuring solar cells are arranged, being in the radiation plane additional reference solar cells for comparative measurements are also arranged can be. This affects the reference solar cells in any case the same radiation as on the solar cells to be measured. It can then, for example, the solar cells to be measured are designed in such a way that at least a first solar cell layer over a second solar cell layer is arranged, the solar cell layers being different Have absorption behavior. Such solar cells are also known as multi-junction solar cells known. The reference solar cells then become a guarantee a clearest possible reference measurement by at least one first reference solar cell layer with an absorption behavior that the corresponds to at least a first solar cell layer and by at least a second reference solar cell layer adjacent to the first reference solar cell layer, their absorption behavior of the second solar cell layer corresponds, formed, wherein the second reference solar cell layer is a filter is connected upstream, the absorption behavior of the first solar cell layer equivalent. The same applies to possible further solar cell layers. The reference solar cell layers are independent of each other, but they nevertheless simulate the conditions within the one above the other Solar cell layers that need to be measured. The arrangement can naturally also for the measurement of single junction solar cells preferably with the help of reference solar cells.

A special exemplary embodiment is described below with reference to FIGS. 1 to 3 explained.

Fig. 1:

Sonnensimulator nach der vorliegenden Erfindung

Fig. 2:

Vergrößerte Detaildarstellung der Strahlungsquelle des erfindungsgemäßen Sonnensimulators

Fig. 3:

Schematische Darstellung eines Querschnittes durch die Strahlungsquelle nach Fig. 2

Fig. 4:

Sonnensimulator nach Fig. 1 mit zusätzlichen, verschiebbaren Filtern

Fig. 5:

Sonnensimulator nach Fig. 1 mit korrekter Darstellung der Strahlungsquelle

Show it:

Fig. 1:

Sun simulator according to the present invention

Fig. 2:

Enlarged detailed view of the radiation source of the sun simulator according to the invention

Fig. 3:

Schematic representation of a cross section through the radiation source according to FIG. 2

Fig. 4:

1 with additional, movable filters

Fig. 5:

1 with the correct representation of the radiation source

1 schematically shows a sun simulator according to the present invention shown, which has a radiation source 1 in the form of a xenon flash lamp, directly adjacent to one or more mirror elements 7. This is 2 and 3 again clearly shown. The mirror elements 7 lie directly on the tube body of the xenon flash lamp 1. Like the figures show, the flash lamp is helical to a possible to achieve homogeneous radiation. The number and shape of the mirror elements 7 can be adjusted so that as possible over the entire longitudinal extent the flash lamp 1 mirror elements 7 rest directly on the tube body. This is shown by way of example in FIG. 2 for two mirror elements 7. This can in particular via appropriate brackets 6 such as Clamp brackets connected to the tube body of the flash lamp 1, these brackets are preferably metallic. The brackets 6 are to be understood here as part of the mirror elements 7. The Mirror elements 7 are made of aluminum and have a gold coating on. The mirror elements 7 can also consist entirely of gold. It But it can also be provided that the mirror element 7 has a metal layer with an oxide layer, for example aluminum. Alternatively, you can but also the mirror element with a semiconductor layer, for example silicon have an oxide layer, the oxide layer also with another Coating, for example made of aluminum, can be provided. The semiconductor oxide layer can be formed as a thermal oxide layer, as in a thermal oxidation process is generated. Then on the oxide layer Aluminum layer can be applied by vapor deposition. The following is supposed to be from a mirror element 7 made of aluminum with a gold coating become.

In Fig. 1, the radiation source 1 together with the mirror element 7 is only for simplification shown in the paper plane. In fact it is Radiation source 1 as well as the mirror element 7 in a plane perpendicular to Beam direction 10 of the sun simulator arranged. The actual The arrangement of the radiation source 1 and the mirror element 7 is shown in FIG. 5 shown.

As further shown in FIG. 1, there is an electrode at the ends of the flash lamp 1 constant voltage, which is generated by a voltage source 8. This Voltage is designed so that it does not fire the flash lamp 1 sufficient, so it is below the ignition voltage. Typically, through the voltage source 8 a few kilovolts are generated. The is preferably constant voltage between 600 V and 1000 V, especially around 800 V. Furthermore, one is on the mirror elements 7 and / or the brackets 6 High voltage potential applied as an ignition voltage, as shown in FIGS. 1 and 2. That resting on the mirror elements 7 and / or the brackets 6 High voltage potential can, for example, via high voltage source 9 for example, an ignition coil is generated and is typically some ten kilovolts, preferably between 10 kV and 20 kV, in particular about 15 kV. This ignition voltage can now cause a pulsed discharge in the Flash lamp 1 are generated. The ignition voltage ultimately produces only one electric field in the area of the tube body of the flash lamp 1, it flows however practically no current, since the mirror elements 7 and / or the holders 6 are isolated by the tube body of the flash lamp 1.

As already explained, the special type of arrangement of the mirror elements improves 7 immediately adjacent, that is, directly adjacent to the tube body the flash lamp 1 the homogeneity of the radiation, on the one hand by the Reflective effect of the mirror elements 7 (see Fig. 2) by the gold coating advantageous mainly in the infrared range, on the other hand by the effect of the mirror elements 7 and / or the holders 6 as high-voltage electrodes, which during the ignition process the homogeneity of the discharge in the Guarantee flash lamp 1.

Fig. 1 further shows that the flash lamp 1 and the mirror elements 7 over Brackets 11 are connected to a granite support plate 4. This carrier plate has the advantages already mentioned at the beginning. Furthermore, the arrangement flash lamp 1 and mirror elements 7 also surrounded by a housing 2, which in the direction of the radiation direction 10 of the sun simulator in the wall area has a plurality of diaphragm elements 3 arranged one after the other. Becomes the housing, for example, cylindrical, so the panel elements 3 designed as successive concentric rings. Furthermore, at least the aperture elements 3, but ideally also the entire interior of the housing 2, with a low reflective coating provided or made of a low reflective material, so a material that does not reflect scattered radiation, but ideally largely absorbed. This ensures that the sun simulator largely shines like a black body or like a cavity emitter.

The present sun simulator can also be developed in accordance with FIG. 4 be displaceable by perpendicular to the radiation direction 10 Filters 5 are arranged, which are preferably also pushed over one another can, as indicated by the dashed lines in Fig. 4. Such Slidable filters are generally known from DE 201 03 645. Filters 5 can either be the same or different parts of the electromagnetic Suppress radiation from the flash lamp 1, as already described at the beginning has been. The filters 5 are made of quartz glass, e.g. Herasil®.

Claims (9)

Sun simulator, having a pulsed radiation source (1) for generating electromagnetic radiation, at least one mirror element (7) arranged in the region of the radiation source, which reflects portions of the radiation from the radiation source (1) essentially in the direction of the radiation direction (10) of the sun simulator, characterized in that the at least one mirror element (7) is arranged directly adjacent to the radiation source (1), the at least one mirror element (7) is at least partially metallic and at least part of the ignition voltage of the pulsed radiation source is applied to the mirror element (7). Sun simulator according to claim 1, characterized in that the at least one mirror element (7) is planar. Sun simulator according to claim 1 or 2, characterized in that the at least one mirror element (7) has a material or a coating, designed such that the reflection effect of the mirror element (7) is significantly higher in the infrared region than in the UV region. Sun simulator according to claim 3, characterized in that the at least one mirror element (7) has a coating which consists of gold or a gold-containing alloy, at least parts of the mirror element (7) made of gold. Sun simulator according to one of claims 1 to 4, characterized in that the at least one mirror element (7) has a semiconductor layer with an oxide layer, in particular silicon, or a metal layer with an oxide layer, in particular a light metal. Sun simulator according to one of claims 1 to 5, characterized in that the radiation source (1) is curved in its longitudinal extent. Sun simulator according to claim 6, characterized in that the radiation source (1) is annular or helical. Sun simulator according to one of Claims 1 to 7, characterized in that the radiation source (1) is surrounded by a housing (2) which has a plurality of diaphragm elements (3) arranged one behind the other in the radiation direction (10) in the wall region. Sun simulator according to one of claims 1 to 8, characterized in that the radiation source (1) and / or the mirror element (7) is connected via brackets (11) to a carrier plate (4) made of granite.

Images