CalLab PV Cells

Solar Cell Calibrations at CalLab PV Cells

Since our founding in 1986, our mission at CalLab PV Cells is to provide highly precise, reproducible solar cell calibrations and measurements. We invest the time needed to perform precision measurements by hand so we can be certain to attain the optimal contacting solution for each and every cell. Additionally, we are continually researching and designing new contacting adaptations for the variety of cell sizes and metallization designs being brought to market.

All processes in CalLab PV Cells are certified, and the instruments are tested and maintained on a routine basis. This level of quality assurance means that something as seemingly simple as changing a lightbulb triggers a quality control process that can last up to 50 hours. The new lamp will be cleared for CalLab PV Cells measurements only when it reliably reproduces the same measurement values for our array of primary reference cells. To further ensure our commitment to excellence, regular comparison measurements are carried out with other renowned calibration laboratories around the world.


Calibration and Measurement Services



Services for Multi-Busbar and Busbarless Cells


Bifacial Cell Services

Measurement Services for Thin-Film and Tandem Cells

Measurement Procedure

Shadow free multi busbar contacting
© Fraunhofer ISE / Photo: Aleksander Filipovic
Shadow free multi busbar contacting.

Calibration Procedure


  • Area Measurement
    • Each cell is visually inspected and the area is individually measured before calibration.
  • SR Measurements
    • The next step in calibrating your cell is the measurement of the spectral responsivity (SR), which is performed using our filter monochromator-based setup for large-area cells, or our laser-based setup for thin-film cells.
  • IV Measurements
    • To determine the performance of the solar cell, the IV curve is measured under standard testing conditions (STC; 25°C, 1000W/m², AMX). Using the previously measured spectral responsivity, a spectral mismatch correction can be applied to reach the highest level of precision.
  • Data Analysis and Processing
    • When the measurements have been completed, the data is reviewed and calculated based on ISO/IEC 17025. The data is compiled into a certificate to document the results.
  • Certificates Issued
    • Fraunhofer ISE CalLab PV Cells is, since 2008, a DKD (now DAkkS)-accredited Calibration laboratory in accordance with ISO/IEC 17025. This accreditation is for the calibration of wafer-based standard silicon solar cells in laboratory and industrial formats, 20 x 20 mm² to 210 x 210 mm²). Beyond this, CalLab PV Cells possesses calibration know how and experience with solar cells of a variety of other materials and technologies. These calibrations or measurements are carried out using the same sophisticated measurement system and equipment.
    • If, because of specific properties of the measurement object, it is not possible to estimate the measurement uncertainties, a measurement can be documented as a measurement report without giving uncertainties.

Cell Types

IV measurement of 0BB cell under sun-simulator
© Fraunhofer ISE / Photo: Aleksander Filipovic
IV measurement of 0BB cell under sun-simulator.

CalLab PV Cell’s years of experience have provided us with the know-how to accurately measure a wide variety of cell materials and designs. These include, but are not limited to: 

  • Silicon 
  • Monofacial or Bifacial 
  • N-type or P-type
  • Half-cells
  • Shingle cells
  • Zero to multiple busbars
  • Up to M12 (210 x 210 mm²)
  • Encapsulated reference cells
  • Reference and mini modules
  • Thin-Film
  • Tandem
  • III-V
  •  a-Si
  • CIGS
  • CdTe
  • Dye-Sensitized 
  • Organic 
  • Perovskite 
  • Single and multi-junction

Measurements for other cell types are available upon request.


Cells to be calibrated and used as reference cells should meet the following criteria:

  • Cells should be from the bin which represents the center of the performance distribution for a specific technology (reduced spectral mismatch to other bins)
  • Cells must have a smooth, even back side (no stickers)
  • Cells should be stable, i.e. pre-degraded at the manufacturer
  • Spectral responsivity should be as linear as possible
  • Cells should be optically and electrically uniform
  • Shunt resistance Rsh > 2000 Ωcm²


SR measurement of Multi-Busbar Cell
© Fraunhofer ISE / Photo: Aleksander Filipovic
SR measurement of Multi-Busbar Cell.

CalLab PV Cells is accredited by Germany's National Accreditation Body (DAkkS) in accordance with ISO/IEC 17025. The DAkkS is signatory to the International Laboratory Accreditation Cooperation (ILAC) for the mutual recognition of calibration certificates ilac-MRA.

In addition, CalLab PV Cells participates in regular international measurement comparisons to ensure development and maintenance of international standards.

The ISO/IEC 17025 accreditation is granted when the accrediting body, in this case the DAkkS, confirms the technical competence of the laboratory to carry out specific tests or calibrations specific to a Scope of Accreditation (our calibration service) as well as its established, implemented, and continuously improved quality management system. 

We can also provide you with a choice of the following standard conditions for your solar cell calibrations: AM1.5 global, AM1.5 direct or AM0 WRL.

Fraunhofer ISE as well as CalLab PV Cells are ISO 9001-certified.

All of our test equipment is subject to ISO 9001 monitoring and is recalibrated regularly.

The ISO 9001 accreditation evaluates an organizations quality management system. 

Services for Multi-Busbar and Busbarless Cells

Multi busbar cell measurement
© Fraunhofer ISE / Photo: Aleksander Filipovic
Multi busbar cell measurement.

CalLab PV Cells strives to keep pace with the growing demand for more diverse contacting methods for the large variety of cell designs currently on the market. To better serve the current market, we have developed contacting methods to specifically address the unique challenges of busbarless (0BB) and multi-busbar (MBB) cells.

9BB and 12BB cells have become increasingly popular and our new MBB contacting unit was specially designed to provide the highest levels of accuracy when calibrating these types of cells. This unit uses extra thin contacting strips to minimize shading of the active cell area and to ensure that each busbar is fully contacted during the measurements. We have a choice of a gold foil background or a black foil background relevant for bifacial cells for each of these methods. 

For 0BB cells, we apply a GridTouch-based wire setup. There is a choice of wire configurations (10, 20, or 30) for the final measurement that can be chosen to best match your module configuration, as well as a choice of a gold foil background or a black foil background. 

Bifacial Cell Services

Dual sided illumination of bifacial cell
© Fraunhofer ISE / Photo: Aleksander Filipovic
Dual sided illumination of bifacial cell.

Bifacial solar cells have attracted much attention due to their significant energy gain and cost-effectiveness compared to conventional monofacial solar cells.  

At Fraunhofer ISE CalLab PV Cells, we have used our years of experience to design several solutions for the challenges of bifacial measurements. We have designed a special chuck with negligible reflectivity for the most accurate single-sided measurements of bifacial cells, which minimizes the contribution by the non-illuminated cell side. Upon request, we can also perform measurements with a reflective chuck.

We have also developed an advanced measurement setup which allows for selecting between simultaneous, dual-sided illumination or single-sided illumination with elevated irradiance levels. This innovative setup has been optimized in order to detect differences between dual- and single-sided illumination methods with a high degree of accuracy. 

Measurement Services for Thin-Film and Tandem Cells

Perovskit-Si-Tandem Measurement
© Fraunhofer ISE / Photo: Aleksander Filipovic
Perovskit-Si-Tandem Measurement.

Solar cells made of a large variety of materials can be measured at CalLab PV Cells to evaluate their performance. Over the years we have gained considerable experience in adapting the measurement setup for ideal cell mounting and contacting to accommodate new cells and prototypes. We have used this know-how to construct a highly precise, wide range tunable, laser setup which is optimized for the SR measurements of thin-film and small-area solar cells. The laser setup combines a high optical resolution (mainly <5nm) with a high uniformity (<2%). The light beam can be adjusted up to 6". Between our grating monochromator and laser setup, we have the capability of measuring the spectral responsivity in the wavelength range between 300 nm and 2000 nm.

We offer calibration services for a broad range of thin-film single and multijunction solar cells including organic, perovskite, CIGS, CIS, CZTS, a-Si and dye-sensitized cells.

Those calibrations are not restricted to single junction solar cells, but are also available for tandem applications. Combining the expertise of thin film measurements with our strong background in III-V based tandems, we can provide calibrated measurements for thin-film based tandem solar cells like perovskite-silicon solar cells. Cell efficiencies are determined considering pre-conditioning, hysteresis effects, and stability over time.

  • Nitrogen storage is available for all samples.
  • Customized aperture masks can be created for your cells using a laser cutter.
  • Adapted contact schemes for specific metallization designs.

Fraunhofer ISE also has a calibration laboratory dedicated to III-V devices which offers calibrated measurements of III-V multi-junction cells for space and terrestrial concentrator applications as well as of single-junction concentrator solar cells


Jochen Hohl-Ebinger

Contact Press / Media

Dr. Jochen Hohl-Ebinger

CalLab PV Cells

CalLab PV Cells
Heidenhofstr. 2
79110 Freiburg

Phone +49 761 4588-5359

Contact Press / Media

Wendy Schneider

CalLab PV Cells

Fraunhofer ISE
Heidenhofstr. 2
79110 Freiburg

Phone +49 761 4588-5146