From pv journal 05/24
On Jan. 31, 2024, researchers from the Fraunhofer Institute for Photo voltaic Vitality Programs (Fraunhofer ISE) introduced that, alongside perovskite developer Oxford PV, that they had produced a full-sized perovskite tandem module with a conversion effectivity of 25%. At 421 W, the dual-glass module’s energy output is much from that achieved by the large-format modules manufactured by photo voltaic trade giants. Nonetheless, the consequence was a robust demonstration of the steps being made towards commercializing what’s broadly thought-about the subsequent era of photo voltaic cell expertise.
When saying the consequence, the Fraunhofer ISE workforce famous that scientists from its CalLab PV Modules’ calibration laboratory used a “multispectral photo voltaic simulator” to measure each the crystalline silicon photo voltaic cell and perovskite cells. It allowed for various gentle spectra to be utilized to the cell whereas underneath steady illumination. This required specialised measurement gear primarily based on LED gentle sources that had been capable of present illumination evenly throughout the module’s 1.68 m2 floor.
“The continual depth and spectral stability of the sunshine supply is of explicit significance particularly for tandem gadgets,” mentioned Johnson Wong, common supervisor for the Americas at gear supplier Wavelabs. The researchers from Fraunhofer ISE used Wavelabs’ Sinus-3000 Superior LED module I-V tester for the Oxford PV module.
“Due to its optimized gentle distribution over a protracted working distance, the tester gentle supply is designed to forged a light-weight subject that very carefully mimics the solar at each level over the big module space,” Wong added. He mentioned the Sinus-3000 LED tester exceeds A+ class by way of “spectrum, gentle uniformity, and stability over time, which play a crucial position within the measurement accuracy.”
Correct characterization
The correct characterization of perovskite photo voltaic gadgets requires not solely new gear but additionally novel processes. Longer illumination instances are wanted; the temperature influence of the sunshine supply have to be managed or corrected for; I-V sweeps ought to be considerably slower than in crystalline silicon cells; and, in tandem cells, their present have to be aligned in order that the mixed energy output is just not restricted.
The PV analysis group, potential producers, and gear suppliers are making strides in overcoming the formidable challenges posed by perovskite photo voltaic gadgets. New, collaborative analysis initiatives are being launched and measurement routines have gotten extra subtle. In consequence, confidence is rising that as the possible PV perovskite producers develop their gadgets towards maturity, the gear and processes will probably be prepared.
Sunny prospects
Karl Melkonyan, PV expertise analyst with S&P International Commodity Insights, mentioned that perovskite tandems have “the most effective probabilities for commercialization” amongst next-generation photo voltaic cell applied sciences. Perovskite PV cells may be coupled with both crystalline silicon (c-Si) or thin-film photo voltaic cells.
Early perovskite PV gadgets achieved conversion efficiencies within the low single digits – 3.8% was recorded in 2008. Document efficiencies at the moment are set at common intervals and are effectively past 25%.
Perovskite tandem gadgets are extraordinarily promising, primarily as a result of the thin-film perovskite cell plus the “base” c-Si, cadmium telluride, or copper indium gallium selenide layer can seize totally different gentle wavelengths, leading to small-scale analysis cells with efficiencies past 30%.
Translating lab effectivity to bigger cells and modules is troublesome, nevertheless. “Whereas there are numerous report effectivity achievements of perovskite photo voltaic cells reaching 20% and above, the full effectivity of a tandem construction may be a lot decrease than the sum of these particular person efficiencies,” mentioned Melkonyan. He famous that the explanation for that is typically a present mismatch between backside and prime cells.
Measurement challenges
For a PV gadget to show its value, its energy output should have the ability to be measured in a extremely correct, replicable, and standardized vogue. On the finish of the day, if a PV module is to be bought and put in, it’s critical that its nameplate energy output may be trusted.
Right here, as famous within the latest Fraunhofer ISE and Oxford PV consequence, perovskite PV gadgets current a number of recent challenges. “Sure, the facility measurement of a perovskite tandem or multi-junction cell presents challenges and could possibly be fairly troublesome as a result of very particular spectrally-adjustable photo voltaic simulators are required,” mentioned Melkonyan. “Aside from applicable stabilization strategies for various perovskite supplies, the processes ought to embody standardized protocols to measure underneath commonplace take a look at circumstances.”
In late April 2024, Fraunhofer ISE, Oxford PV, Wavelabs, and the College of Freiburg wound up an 11-month investigation into how large-format perovskite tandem PV cells may be precisely characterised. Fraunhofer ISE’s Martin Schubert led the venture – abbreviated to “Katana” in German. He mentioned there are two main variations between the characterization of perovskite tandem gadgets and common PV modules.
Two elements
“One is that the effectivity might change throughout illumination,” mentioned Schubert, who leads the standard assurance, characterization and simulation workforce. “The explanation for that’s that there’s an ion migration within the perovskite cell by which some ions are shifting. The second complication is the tandem structure. By itself, meaning we’ve two photo voltaic cells – one on prime of the opposite and with totally different spectral sensitivity. We have to take care that the highest cell will get the correct amount of present and the underside cell will get the correct amount of present.”
Ion migration throughout the perovskite gadget whereas underneath steady illumination implies that the measured effectivity can both improve or lower over time. This “metastability” necessitates the lengthy illumination time wanted for stabilized energy output to be ascertained. Complicating issues additional, totally different perovskite PV compositions exhibit various ranges of metastability.
The necessity for lengthy gentle publicity, to accommodate metastability, brings warmth, even when utilizing LEDs. Which means that the measurement of perovskite gadgets is commonly carried out at temperatures larger than commonplace take a look at circumstances (STC).
The facility output of a photovoltaic gadget declines as its temperature will increase, an element described as a tool’s temperature coefficient. Totally different PV applied sciences imply differing temperature coefficients. c-Si photo voltaic merchandise, for instance, have a bigger temperature coefficient than skinny movie gadgets. If that isn’t managed and accounted for, the result’s measurement uncertainty.
Testing gear with temperature management – basically a chamber with air-con – can scale back this uncertainty in best-case eventualities. Such subtle gadgets, notably with ample scale to accommodate full modules, come at a value.
The influence of temperature may be corrected for utilizing mathematical fashions primarily based on correct temperature readings and might account for the uncertainty larger temperatures can deliver. With tandem gadgets, the temperature sensitivity of each the highest and backside cell have to be accounted for – a posh, if not unattainable, equation.
Business implications
At current, the testing of perovskite gadgets is carried out inside minutes, to account for metastability associated to ion migration within the perovskite cell, in order that slower I-V sweeps, with a number of energy level monitoring (MPPT), may be carried out. That is unsuitable for mass manufacturing, as many modules must be rolling off manufacturing traces each minute.
Wavelabs’ Wong mentioned {that a} “extra pragmatic take a look at routine” would seemingly first contain a preconditioning of the module utilizing gentle soaking, from mass-production gentle sources. That might then be adopted by “a quick I-V sweep utilizing prime quality illumination that should match throughout the specs of spectral match, uniformity, and stability,” mentioned Wong. “The quick I-V sweep will seemingly be performed within the order of 100 milliseconds to at least one second, throughout which the ions are ‘frozen in’ to their preconditioned distribution and don’t considerably redistribute.”
Fraunhofer ISE will probably be launching a three-year analysis venture in Could 2024 that can examine how “quick and exact measurements” may be developed and executed for perovskite gadgets, together with tandems. The venture, abbreviated to “PERLE” in German, will probably be funded by Germany’s Federal Ministry of Financial Affairs and Local weather Motion. Fraunhofer ISE’s Schubert mentioned that it’s attainable that the primary findings from the venture will probably be printed by Could 2025.
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