23 percent efficiency for Perovskite-CIGS-tandem
MiaSolé and Solliance establish new world record conversion efficiency for flexible solar cel
Nine months after the presentation of the first record breaking flexible solar cell, USA based MiaSolé Hi-Tech Corp and European Solliance Solar Research have established a new world record power conversion efficiency of 23 percent on a flexible solar cell. The solar cell combines two thin-film solar cell technologies into a tandem solar cell stack: a top flexible semi-transparent perovskite solar cell with a bottom flexible CIGS cell.
A tandem solar cell, which combines a semi-transparent perovskite cell and a CIGS cell, has the potential for high conversion efficiency exceeding single junction solar cell performance thanks to tuneable and complementary band gaps of these individual thin film solar cells.
In order to realise maximum conversion efficiencies, the absorption properties of the top perovskite cell and of the bottom CIGS cell should be tuned to complement each other. The perovskite solar cell was deposited on a transparent and flexible substrate, employed transparent conductive electrodes, and was optimised for maximum visible light conversion efficiency and infrared light transparency to allow the majority of infrared light to reach the bottom CIGS cell.
CIGS technology has a proven track record as a high efficiency and stable solar technology and has entered high volume manufacturing in multi-GW scale around the world. CIGS technology has been successfully used to produce high efficiency flexible and lightweight cells and modules, which address markets where heavy and rigid panels cannot be used.
Perovskite solar cells, despite being a relatively young technology, have already achieved high efficiencies, and promise low cost solar technology based on abundant materials. Combining both technologies in a flexible and lightweight package expands the horizon of high performance, flexible, and customizable solar technology.
Strong collaboration
The CIGS bottom cell was developed by MiaSolé Hi-Tech, a provider of CIGS production turn-key factories and manufacturer of CIGS flexible solar panels, located in Santa Clara, California. The CIGS cell used in this tandem architecture is based on a commercially available high efficiency flexible solar cell technology fabricated on lightweight stainless-steel foil using a proprietary high throughput roll-to-cell sputtering process. Recently, MiaSolé reported a flexible large area certified module efficiency of 17.44 percent with an active area of 1.08 m2.
As a result of the combined expertise of MiaSolé Hi-Tech in CIGS development and manufacturing and the Solliance team in the area of perovskite technology, a new record efficiency flexible perovskite/CIGS tandem cell was produced. ”A highly efficient flexible hybrid solar cell is an outlook on how perovskite solar cell technology can innovate the established solar technology, leading to a different application area with improved performance” according to Sjoerd Veenstra, program manager for Perovskite-based Solar Cells at Solliance.
“This significant tandem cell performance gain was achieved through process improvements in the bottom CIGS cell”, adds director of technology at MiaSolé Hi-Tech Dmitry Poplavskyy, “These process changes, implemented by MiaSolé, enable high efficiency CIGS cells with the spectral response better matched to the top perovskite cell. Further improvements in spectral matching as well as overall higher CIGS cell efficiency are expected to push the tandem architecture well beyond 23 percent”.
