Imec, an innovation hub in nanoelectronics, energy and digital technologies, debuted a perovskite/CIGS thin-film tandem solar cell that achieved a record efficiency of 24.6 percent. The thin-film tandem solar cell was made up of a top perovskite cell that Imec developed within the partnerships with EnergyVille and Solliance, and a bottom CIGS cell from the Centre for Solar Energy and Hydrogen Research (ZSW, Stuttgart, Germany).
The perovskite top cell of the tandem device uses light in the visible part of the solar spectrum. However, the underlying CIGS cell harvests the light in the near-IR spectrum that passes through the perovskite cell. With this combination of solar cell technologies, the tandem cell significantly outperforms the stand-alone perovskite and CIGS cells. Moreover, both perovskite and CIGS cells are thin-film solar cells. Therefore, further development of the technology could lead to high efficiency flexible solar cells and building integrated photovoltaic (BIPV) solutions.
Tandem Cell Made of Perovskite Cell on a CIGS Cell
The 4-terminal tandem cell consists of a perovskite solar cell stacked on top of a CIGS cell. According to Imec, the device is based on a fully scalable concept to enable the industrial adoption of the process. Imec cited several innovations that resulted in the new record efficiency of 24.6 percent. First, Imec says it added optical coupling layers to the tandem stack and optimized the transparent electrodes thereby letting more of the near IR light through the perovskite layer. Secondly, Imec optimized the perovskite layer in terms of a wide bandgap of 1.72eV for higher tandem efficiency.
ZSW fabricated the CIGS cell of 0.5cm² size on its the high-efficiency line, which employs all the optimized processes necessary for the preparation of record-setting solar devices. Imec and ZWS assert that further improvements of the technology will lead to thin-film tandem solar cells with efficiencies of more than 30 percent.