Netherlands based solar research organization Solliance along with Hanergy's US based copper indium gallium selenide (CIGS) PV products thin-film manufacturer MiaSole Hi-Tech Corp has achieved 21.5% power conversion efficiency by combining 2 thin-film solar cell technologies into a 4 terminal tandem solar cell stack.
For the purpose of this research, the team put together a top flexible semi-transparent perovskite solar cell with a bottom flexible CIGS cell. The latter was developed by MiaSole using high efficiency flexible solar cell technology fabricated on lightweight stainless-steel foil using a proprietary high throughput roll-to-cell sputtering process.
The team deposited a perovskite solar cell on a transparent and flexible substrate and used transparent conductive electrodes. The cell was then optimized for maximum visible light conversion efficiency and infrared light transparency to allow the majority of infrared light to reach the bottom CIGS cell.
"As single junction efficiencies get closer to the theoretical limits, improving module performance while continuously reducing $/W costs becomes more difficult," said Director of Technology at MiaSole Hi-Tech, Dmitry Poplavskyy. "We believe that combining our core CIGS technology with a low-cost perovskite technology in a tandem architecture will allow us to achieve high module efficiencies while maintaining low $/W costs."
In September 2018, Belgium's Imec announced achieving 24.6% efficiency for a perovskite CIGS tandem cell in partnership with EnergyVille and Solliance when the team used a bottom CIGS cell from Germany's Centre for Solar Energy and Hydrogen Research (ZSW) (see Higher Efficiency For Imec's nPERT & Tandem CIGS Cell).