From pv magazine 05/24
On Jan. 31, 2024, researchers from the Fraunhofer Institute for Solar Energy Systems (Fraunhofer ISE) announced that, alongside perovskite developer Oxford PV, they had produced a full-sized perovskite tandem module with a conversion efficiency of 25%. At 421 W, the dual-glass module’s power output is far from that achieved by the large-format modules manufactured by solar industry giants. Nonetheless, the result was a powerful demonstration of the steps being made toward commercializing what is widely considered the next generation of solar cell technology.
When announcing the result, the Fraunhofer ISE team noted that scientists from its CalLab PV Modules’ calibration laboratory used a “multispectral solar simulator” to measure both the crystalline silicon solar cell and perovskite cells. It allowed for different light spectra to be applied to the cell while under continuous illumination. This required specialized measurement equipment based on LED light sources that were able to provide illumination evenly across the module’s 1.68 m2 surface.
“The continuous intensity and spectral stability of the light source is of particular importance especially for tandem devices,” said Johnson Wong, general manager for the Americas at equipment provider Wavelabs. The researchers from Fraunhofer ISE used Wavelabs’ Sinus-3000 Advanced LED module I-V tester for the Oxford PV module.
“Thanks to its optimized light distribution over a long working distance, the tester light source is designed to cast a light field that very closely mimics the sun at every point over the large module area,” Wong added. He said the Sinus-3000 LED tester exceeds A+ class in terms of “spectrum, light uniformity, and stability over time, which play a critical role in the measurement accuracy.”
Accurate characterization
The accurate characterization of perovskite solar devices requires not only new equipment but also novel processes. Longer illumination times are needed; the temperature impact of the light source must be controlled or corrected for; I-V sweeps should be significantly slower than in crystalline silicon cells; and, in tandem cells, their current must be aligned so that the combined power output is not limited.
The PV research community, prospective manufacturers, and equipment suppliers are making strides in overcoming the formidable challenges posed by perovskite solar devices. New, collaborative research projects are being launched and measurement routines are becoming more sophisticated. As a result, confidence is growing that as the prospective PV perovskite manufacturers develop their devices toward maturity, the equipment and processes will be ready.
Sunny prospects
Karl Melkonyan, PV technology analyst with S&P Global Commodity Insights, said that perovskite tandems have “the best chances for commercialization” among next-generation solar cell technologies. Perovskite PV cells can be coupled with either crystalline silicon (c-Si) or thin-film solar cells.
Early perovskite PV devices achieved conversion efficiencies in the low single digits – 3.8% was recorded in 2008. Record efficiencies are now set at regular intervals and are well beyond 25%.
Perovskite tandem devices are extremely promising, primarily because the thin-film perovskite cell plus the “base” c-Si, cadmium telluride,