INSTITUTION PROFILE / PEROVSKITE SOLAR CELLS
Fraunhofer ISE
The German institute that both measures and makes tandem solar cells
Fraunhofer ISE (the Fraunhofer Institute for Solar Energy Systems) is an applied research institute in Freiburg, in south-west Germany. If record announcements for perovskite solar cells often include the line "certified by Fraunhofer ISE CalLab", it is because the institute runs an accredited calibration laboratory for solar cells. At the same time, it operates a research line that builds perovskite-silicon tandems in a form close to mass production. This profile looks at one question only: how much influence Fraunhofer ISE actually has over perovskite solar cells.
What this article covers
- Fraunhofer ISE in 30 seconds
- What kind of body it is: the four types of influence
- What it does for perovskite solar cells
- How far its influence reaches (powers and geography)
- The companies and organisations involved
- Outlook
- Glossary, references and claim-to-source audit
1. Fraunhofer ISE in 30 seconds
FULL NAMEFraunhofer Institute for Solar Energy Systems ISEFraunhofer ISE
COUNTRYGermanyBased in Freiburg, Baden-Württemberg
TYPE OF BODYAn institute of the Fraunhofer-GesellschaftAn applied research institute whose stated aim is to transfer technology to industry and society
ESTABLISHED1 July 1981Spun off from a Fraunhofer IAF working group on solar energy systems
STAFF1,366As of 31 December 2025. The official website describes it as having "around 1,300 staff" and being "one of the world's largest solar research institutes"
BUDGET€128.3 millionRevenue for 2025 (preliminary). All fields combined
ROLE IN PEROVSKITE SOLAR CELLSCertified efficiency measurement and tandem R&DNo power to set regulations or subsidies
REACHMeasurement is global; research centres on German and European industryIts calibration certificates are recognised internationally under the ILAC mutual recognition arrangement
The one thing to grasp first
NLR's efficiency chart names Fraunhofer ISE as one of the example labs that confirm the records it lists Sourced. Counting the 58 entries in the chart's data table whose cell type includes perovskite, 11 list "FhG-ISE" as the measuring lab, the second-highest number after Newport (17) Our calculation. In other words, Fraunhofer ISE is one of the main bodies that verify perovskite and tandem records for the world. It also researches tandems itself, so it appears on both sides: measuring and making.
2. What kind of body it is: the four types of influence
Unlike the companies in this series, none of the institutions that appear in perovskite solar cell coverage mass-produces solar cells. What separates them is the route by which they influence the industry, and that gives four types.
3. What it does for perovskite solar cells
Fraunhofer ISE's involvement runs along two lines: certified measurement (CalLab) and research and development Sourced.
| Activity | What it involves | Link to perovskites | Reach |
|---|---|---|---|
| CalLab PV Cells (cell calibration laboratory) | Has calibrated solar cells since 1986. Since 2008 it has been a calibration laboratory accredited to ISO/IEC 17025 by DAkkS, Germany's national accreditation body. The accreditation covers wafer-based standard silicon cells (20 x 20 mm² to 210 x 210 mm²) | Perovskite and tandem (multi-junction) cells are measured on the same equipment. Where the uncertainty cannot be estimated for a sample, the result is issued as a measurement report without uncertainties | Global (DAkkS is a signatory to the ILAC mutual recognition arrangement) |
| CalLab PV Modules (module calibration laboratory) | One of only five accredited calibration laboratories for PV modules worldwide, and the only one in Germany. Measurement uncertainty of ±1.1% for monofacial modules. Characterises more than 7,000 modules a year | Measures perovskite-silicon tandem modules using a solar simulator with LED light sources | Global |
| Developing tandem measurement methods (Katana project) | With funding from what was then the German Federal Ministry for Economic Affairs and Climate Action (BMWK), developed methods for characterising perovskite-based tandem modules. A Wavelabs solar simulator (18,400 LEDs, 28 spectral channels) was installed at CalLab PV Modules | The institute says it is important to provide "highly precise and reproducible measurements" as soon as possible so that there can be "objective competition" | A German project, but the methods underpin international comparisons |
| Taking part in standards work | Supports standards development in working groups WG 2 and WG 7 of the IEC's photovoltaic technical committee (TC 82) | Working on extending the calibration of multi-junction cells to larger areas | International (IEC member countries) |
| Pero-Si-SCALE (tandem scale-up pilot line) | A research line that makes and evaluates perovskite-silicon cells and modules on the industrial M12 wafer format. Built with completion planned for the end of 2024 | The annual report says a "hybrid route" combining evaporation and solution coating has achieved efficiencies above 33% | Explicitly aimed at supporting the German and European solar industry |
| Perovskite thin-film PV research | Makes cells and modules by low-temperature deposition and printing from solution. Also covers flexible substrates, perovskite-perovskite tandems and long-term stability | Aimed at film-type (flexible) uses and integrated PV, for example in buildings | Research at an international level, acting as a point of contact for industry and academia |
A materials engineer's view: check the scope of "certified"
CalLab PV Cells' accreditation covers standard silicon cells. Perovskite and tandem cells are measured with the same equipment and procedures, but the lab states that where the uncertainty cannot be estimated, the result becomes a measurement report without uncertainties Sourced. The annual report also notes that perovskites have material-specific metastability (characteristics that can change during measurement), and that tandems need special analysis methods. When using record figures to evaluate materials, it is safest to check whether you are looking at a certificate or a report, and what the area and measurement conditions were. See also our explainers on conversion efficiency and evaluation metrics, and on tandem cells.
4. How far its influence reaches (powers and geography)
| Aspect | What Fraunhofer ISE has | What it does not have |
|---|---|---|
| Powers | The ability to issue calibration certificates under its DAkkS accreditation. A seat in IEC working groups that draft standards | Power to decide standards (the IEC decides). Power to set regulations or subsidies. Power to decide what goes on NLR's chart |
| Geography | Its measurement services are used by companies and research bodies worldwide (LONGi in China, KIER in South Korea, the Anglo-German Oxford PV and others). Its research line is aimed at supporting German and European industry | Any direct authority over other countries' markets or certification systems |
| Role in records | Named on NLR's chart as an example of a confirming lab, and measured 11 perovskite-related records | It is not the sole arbiter of records. NLR, JRC-ESTI, JET and others also confirm them |
| Scale | 1,366 staff; revenue of €128.3 million in 2025 (preliminary, all fields) | The budget spent on perovskites and tandems alone has not been published |
A note on reading the numbers
The €128.3 million covers all fields combined, including solar, power, heat and hydrogen. According to the annual report, the 30% cut in public energy research funding in 2024 made itself felt with a delay, and in 2025 the institute had to reduce staff, contrary to its plans Sourced. Revenue fell from €157.8 million in 2024 to €128.3 million in 2025 (preliminary). How much of this went to perovskites and tandems has not been published Not yet confirmed.
5. The companies and organisations involved
Links to the company profiles in this series
| Company | Link to Fraunhofer ISE (as stated in primary sources) | Link to this series |
|---|---|---|
| Oxford PV | Using Oxford PV's tandem cells, Fraunhofer ISE built a 1.68 m², 421 W module with 25% efficiency (January 2024). Oxford PV's 60-cell module at 26.9% was measured and certified by Fraunhofer CalLab (Oxford PV announcement, June 2024). In June 2026 the two jointly built a module with 25.6% efficiency using "matrix shingled" interconnection, in which cells overlap like roof tiles | See our Oxford PV profile |
| LONGi | Fraunhofer ISE certified LONGi's 30.1% perovskite-silicon tandem cell on an M6-size wafer (LONGi announcement, June 2024) | See our LONGi profile |
6. Outlook
| What the evidence suggests | Primary information it rests on | Category |
|---|---|---|
| The closer tandem modules get to mass production, the more prominent Fraunhofer ISE becomes as a lab that can measure large-area tandems | CalLab PV Modules is one of five accredited module calibration labs in the world and has a simulator for tandem modules. The annual report describes work on extending multi-junction cell calibration to larger areas | Inference |
| The focus of its R&D will shift towards transferring technology to European production lines | Pero-Si-SCALE is aimed at supporting German and European industry and has built an M12 research line. Joint development with Oxford PV continues at full module size | Inference |
| If public funding cuts continue, the scale of tandem research will depend more on money from foundations and companies | The annual report records the 30% cut in public energy research funding in 2024 and the staff reduction, while also noting that the Werner Siemens Foundation will provide €14 million for tandem solar cell research until 2032 | Inference |
7. Glossary
- CalLab
- Fraunhofer ISE's calibration laboratories, with one for cells (PV Cells) and one for modules (PV Modules).
- DAkkS
- Germany's national accreditation body. As a signatory to the ILAC mutual recognition arrangement, certificates from labs it accredits are more readily accepted internationally.
- ISO/IEC 17025
- The international standard for accrediting the competence of testing and calibration laboratories.
- Hybrid route
- A method of making the perovskite layer by combining vacuum evaporation with deposition from solution. It can coat silicon with a pyramid-textured surface.
- M12 and M6
- Names of standard silicon wafer sizes. M12 is 210 mm on a side.
8. References
- Fraunhofer ISE About Fraunhofer ISE: around 1,300 staff, one of the world's largest solar research institutes. https://www.ise.fraunhofer.de/en/about-us.html
- Fraunhofer ISE Data and Facts: 1,366 staff as of 31 December 2025. https://www.ise.fraunhofer.de/en/about-us/data-and-facts.html
- Fraunhofer ISE Annual Report 2025/26: revenue trend, the 30% cut in public funding in 2024 and staff reduction, Werner Siemens Foundation support, WG 2 and WG 7 of IEC TC 82, CalLab, above 33% with the hybrid route, and Pero-Si-SCALE. https://www.ise.fraunhofer.de/content/dam/ise/en/documents/annual_reports/fraunhofer-ise-annual-report-2025-2026.pdf
- Fraunhofer ISE In Memory of Prof. Adolf Goetzberger: founding on 1 July 1981. https://www.ise.fraunhofer.de/en/in-memory-of-prof-goetzberger.html
- Fraunhofer ISE CalLab PV Cells: calibration since 1986, DAkkS accreditation since 2008 and its scope, measurement of perovskite and tandem cells, and ILAC mutual recognition. https://www.ise.fraunhofer.de/en/rd-infrastructure/accredited-labs/callab/callab-pv-cells.html
- Fraunhofer ISE CalLab PV Modules: one of five accredited module calibration labs worldwide, ±1.1%, and more than 7,000 modules a year. https://www.ise.fraunhofer.de/en/rd-infrastructure/accredited-labs/callab/callab-pv-modules.html
- Fraunhofer ISE Press release, "Accurately Determine Efficiency of Perovskite-Silicon Tandem PV Modules" (22 May 2023): the Katana project and the Wavelabs simulator. https://www.ise.fraunhofer.de/en/press-media/press-releases/2023/accurately-determine-efficiency-of-perovskite-silicon-tandem-pv-modules.html
- Fraunhofer ISE News, "Technology Platform for the Scale-Up of Perovskite-Silicon Tandem Photovoltaics Gets the Go-Ahead" (5 June 2023): Pero-Si-SCALE, M12, completion planned for the end of 2024. https://www.ise.fraunhofer.de/en/press-media/news/2023/technology-platform-scale-up-perovskite-silicon-tandem-photovoltaics-gets-go-ahead.html
- Fraunhofer ISE News, "Scalable Perovskite Silicon Solar Cell with 31.6 Percent Efficiency Developed" (25 September 2024): exchange with KAUST and certification by CalLab. https://www.ise.fraunhofer.de/en/press-media/news/2024/scalable-perovskite-silicon-solar-cell-with-31-point-6-percent-efficiency-developed.html
- Fraunhofer ISE Press release, "Oxford PV and Fraunhofer ISE Develop Full-sized Tandem PV Module with Record Efficiency of 25 Percent" (31 January 2024). https://www.ise.fraunhofer.de/en/press-media/press-releases/2024/oxford-pv-and-fraunhofer-ise-develop-full-sized-tandem-pv-module-with-record-efficiency-of-25-percent.html
- Fraunhofer ISE Press release, "Perovskite-silicon solar cells meet matrix shingled interconnection" (18 June 2026): a 25.6%-efficient module using Oxford PV cells. https://www.ise.fraunhofer.de/en/press-media/press-releases/2026/perovskite-silicon-solar-cells-meet-matrix-shingled-interconnection.html
- Fraunhofer ISE Research topic, "Perovskite Thin-Film Photovoltaics": low-temperature solution deposition and printing, flexible substrates, and perovskite-perovskite tandems. https://www.ise.fraunhofer.de/en/business-areas/photovoltaics-materials-cells-and-modules/perovskite-thin-film-photovoltaics.html
- NLR Best Research-Cell Efficiency Chart: lists Fraunhofer-ISE as an example of an independent test lab that confirms records. https://www.nlr.gov/pv/cell-efficiency
- NLR Research-cell efficiency data table: measuring lab for each record, as of the July 2026 revision. https://www.nlr.gov/docs/libraries/pv/cell-efficiency-data-table.xlsx
- LONGi News release, "LONGi announces the new world record efficiency of 30.1% for the commercial M6 size wafer-level silicon-perovskite tandem solar cells" (19 June 2024): certified by Fraunhofer ISE. https://www.longi.com/en/news/is-m6-wafer-silicon-perovskite-tandem-cells-new-efficiency-record/
- Oxford PV Press release, "Oxford PV debuts residential solar module with record-setting 26.9% efficiency" (19 June 2024): measured and certified by Fraunhofer CalLab. https://www.oxfordpv.com/press-releases/oxford-pv-solar-sustainability-initiative
9. Claim-to-source audit
| Claim in the article | Category | Source |
|---|---|---|
| Around 1,300 staff; one of the world's largest solar research institutes | Sourced | Reference 1 https://www.ise.fraunhofer.de/en/about-us.html |
| 1,366 staff as of 31 December 2025 | Sourced | Reference 2 https://www.ise.fraunhofer.de/en/about-us/data-and-facts.html |
| Revenue of €157.8 million (2024) and €128.3 million (2025, preliminary), the 30% cut in public funding and staff reduction, €14 million from the Werner Siemens Foundation, WG 2 and WG 7 of IEC TC 82, above 33% with the hybrid route, extending multi-junction calibration to larger areas, metastability in tandems | Sourced | Reference 3 https://www.ise.fraunhofer.de/content/dam/ise/en/documents/annual_reports/fraunhofer-ise-annual-report-2025-2026.pdf |
| Founded 1 July 1981 as a spin-off from a Fraunhofer IAF group | Sourced | Reference 4 https://www.ise.fraunhofer.de/en/in-memory-of-prof-goetzberger.html |
| CalLab PV Cells: calibration since 1986, timing and scope of DAkkS accreditation, measurement of perovskite and tandem cells, reports without uncertainties, ILAC mutual recognition | Sourced | Reference 5 https://www.ise.fraunhofer.de/en/rd-infrastructure/accredited-labs/callab/callab-pv-cells.html |
| One of five accredited module calibration labs worldwide, ±1.1%, more than 7,000 modules a year | Sourced | Reference 6 https://www.ise.fraunhofer.de/en/rd-infrastructure/accredited-labs/callab/callab-pv-modules.html |
| The Katana project, the simulator's specifications, and measurement for "objective competition" | Sourced | Reference 7 https://www.ise.fraunhofer.de/en/press-media/press-releases/2023/accurately-determine-efficiency-of-perovskite-silicon-tandem-pv-modules.html |
| Pero-Si-SCALE's content, M12, completion planned for the end of 2024, support for German and European industry | Sourced | Reference 8 https://www.ise.fraunhofer.de/en/press-media/news/2023/technology-platform-scale-up-perovskite-silicon-tandem-photovoltaics-gets-go-ahead.html |
| The 31.6% cell, exchange with KAUST, certification by CalLab | Sourced | Reference 9 https://www.ise.fraunhofer.de/en/press-media/news/2024/scalable-perovskite-silicon-solar-cell-with-31-point-6-percent-efficiency-developed.html |
| A 1.68 m², 421 W, 25%-efficient module using Oxford PV cells | Sourced | Reference 10 https://www.ise.fraunhofer.de/en/press-media/press-releases/2024/oxford-pv-and-fraunhofer-ise-develop-full-sized-tandem-pv-module-with-record-efficiency-of-25-percent.html |
| A 25.6%-efficient module with matrix shingled interconnection | Sourced | Reference 11 https://www.ise.fraunhofer.de/en/press-media/press-releases/2026/perovskite-silicon-solar-cells-meet-matrix-shingled-interconnection.html |
| Content of perovskite thin-film PV research (flexible substrates, perovskite-perovskite) | Sourced | Reference 12 https://www.ise.fraunhofer.de/en/business-areas/photovoltaics-materials-cells-and-modules/perovskite-thin-film-photovoltaics.html |
| NLR's chart names Fraunhofer-ISE as an example of a confirming lab | Sourced | Reference 13 https://www.nlr.gov/pv/cell-efficiency |
| FhG-ISE is the measuring lab for HZB's 29.15% and KIER's 26.7% | Sourced | Reference 14 https://www.nlr.gov/docs/libraries/pv/cell-efficiency-data-table.xlsx |
| Of 58 entries including perovskite, 11 measured by FhG-ISE, second after Newport's 17 | Our calculation | Our own count from the data table in reference 14 |
| Fraunhofer ISE certified LONGi's 30.1% M6-size tandem cell | Sourced | Reference 15 https://www.longi.com/en/news/is-m6-wafer-silicon-perovskite-tandem-cells-new-efficiency-record/ |
| Fraunhofer CalLab measured and certified Oxford PV's 26.9% 60-cell module | Sourced | Reference 16 https://www.oxfordpv.com/press-releases/oxford-pv-solar-sustainability-initiative |
| The four types of institution and Fraunhofer ISE's place among them, and the choice of records in Fig. 2 | Our calculation | Our own classification and selection |
| The budget spent on perovskites and tandems alone | Not yet confirmed | Not stated in references 2 or 3; this article does not estimate it |
| The three points in the outlook (section 6) | Inference | This article's reading of references 3, 6, 8, 10 and 11 |
Last updated 25 September 2026 / Troy Technical
All figures come from Fraunhofer ISE's official website, annual report and press releases, NLR's efficiency chart data table, and official announcements by the companies concerned. Items marked "Inference" are this article's reading of the primary information, not statements by Fraunhofer ISE.