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Products Isotype Sensors

BPI Isotype Sensor

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Technical Data

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This innovative sensor is based on III-V material isotype solar cells. These cells have the same layer composition than standard III-V multijunction solar cells, but only one pn-junction. The subcells without a pn-junction act as optical filters. Using these cells, the spectral composition of the sunlight and its effects on CPV modules with triple-junction cells can be determined. Main features include:

• Lattice matched isotype detector cells: top cell (Ga0.5In0.5P), middle cell (Ga0.99In0.01As), bottom cell (Ge)

• Hermetic sealing of detector cell for maximum accuracy and enduring outdoor performance.

• Detachable collimator tubes with high straylight rejection

• Sensors calibrated under AM1.5d ASTM G173 spectrum at 1000 W/m2

• C-mount optics interface: Customize your isotype sensor with optical parts out of the catalog: optical filters, baffles or collimators with different viewing angles

   Download file Download Specification


The isotype sensor delivers information about the spectral composition of the solar radiation. The result gives a direct picture about how the subcells in a multi-junction system are performing. Using the isotype sensor, you can

  • Measure the variations in the spectral composition of solar radiation
  • Find out if a location is suitable for a multi-junction cell technology or not
  • Install it on a experimental setup and find out which of the latest ideas for module development work best under different spectral conditions
  • Monitor the influence of spectral changes on the efficiency of a power plant
  • See how the current solar cell or module concept can be improved to get a higher annual energy yield

Measurement Accuracy

The measurement accuracy of these sensors is basically limited by the calibration accuracy used to qualify the sensor. Calibration accuracies are stated at 3 - 5 % for the most advanced calibration labs today. For critical measurements, an annual recalibration should be sheduled to maintain the high measurement accuracy. Each cell is hermetically sealed in a nitrogen atmosphere in our IT sensors to provide the ultimate stability even in the harshest conditions.

The spectral response of a component cell should be matching the spectral response of the system to be monitored with the sensor as closely as possible. Nevertheless, a complete match is not possible due to variations in cell processing and packaging materials. At Black Photon Instruments, we have examined the error that is associated with these differences in great detail and worked closely with Fraunhofer ISE on this topic. Using an empiric mismatch function, the error associated with a mismatch between the sensor and the power plant monitored) can be greatly reduced. The results of this research have been published in the paper "Spectral Measurements with Component Cells - Examinations on Measurement Precision" at the 26th European Photovoltaic Solar Energy Conference and Exhibition in Hamburg 2011.
Download the preprint: Download this file (PVSEC_Hamburg_2011_Jaus_Component_Cells.pdf) PVSEC_Hamburg_2011_Jaus_Component_Cells.pdf.

Note: For the final version of the pdf, please check the pdf conference proceedings.


Our standard cells are lattice matched Ga0.5In0.5P / Ga0.99In0.01As / Ge isotype cells produced by Fraunhofer ISE. These cells are the right choice for most of the systems currently installed from almost all commerical cell manufacturers. We also have metamorphic sensors available, they are introduced as these new cells currently are gaining market share. Although these two cell sets have representative spectral responses, there are some applications were custom isotype solar cells make sense. With our experienced partners and based on almost 10 years experience in cell packaging, we are able to do the packaging of almost any little piece of fragile semiconductor into a robust sensor from the scratch. Challenges welcome!


HermeticPackage Icon    Learn more about the
   technologies employed in our sensors. 

Measurement Principle

IT-Sensor Principle v01    Learn more about the
   measurement principles of our isotype spectral sensors.


Several research papers have been published in the last years on the topic of isotype junction solar cells. The list below is just a selection - if a specific paper is missing, let us know!

K. Araki and M. Yamaguchi: "Influences of spectrum change to 3-junction concentrator cells", Solar Energy Materials & Solar Cells 75 (2003) 707–714

C. Domínguez, I. Antón, and G. Sala, "Spectrum Controlled Solar Simulator for factory testing of CPV modules," in 23rd European Photovoltaic Solar Energy Conference Valencia, Spain, 2008, pp. 887-881.

J. Leloux, D. Pachón, and G. Sala: "Spectral Solar Radiation Measurements and Models for CPV Module Production Estimation", CPV‐6, Freiburg, Germany, AIP Conf. Proc. 1277, pp. 329-332 

G. Peharz, G. Siefer, and A.W. Bett: "A simple method for quantifying spectral impacts on multi-junction solar cells", Solar Energy 83 (2009) 1588–1598 

Wikipedia page on Multijunction Solar Cells

Last Updated on Wednesday, 30 April 2014 20:58