EPFL and Panasonic researchers have announced that they have stabilised perovskite solar cells by integrating rubidium into them. The innovation pushes power-conversion efficiency to 21.6%, which the researchers believe will usher in a new generation of perovskite solar cells.
Perovskite solar cells have great potential for providing cost-effective solar energy. However, heat stability is an issue, and can significantly limit the solar cell’s long-term efficiency, as the cell’s structure can degenerate over time. A solution has been to mix perovskites with other materials, such as cesium, that can improve the cell’s stability without compromising its efficiency in converting light into electrical current. The work was recently published in Science.
Michael Grätzel’s lab at EPFL has now integrated rubidium cations into perovskites, maintaining exceptional stability over 500 continuous hours in full sunlight at 85°C, while pushing power-conversion efficiency to a reported record value of 21.6%. The lab has already submitted a patent based on their innovation.
Figure: EPFL - A cross-section of a perovskite solar cell seen through a scanning electron microscope
This work represents a collaboration between EPFL's Laboratory of Photonics and Interfaces and Laboratory of Photomolecular Science with the Materials Research Laboratory of the Panasonic Corporation.
It was funded by Horizon 2020 (Marie Skłodowska Curie fellowship) the European Union's Seventh Framework Programme for Research (FP7), the Swiss National Science Foundation (SNSF; Umbrella project) the NRP 70 "Energy Turnaround", CONNECT PV, SNF-NanoTera, the Swiss Federal Office of Energy (SYNERGY), and the King Abdulaziz City for Science and Technology (KACST).
Michael Saliba, project lead, said, "I have shown that perovskite cells built with rubidium make available voltage close to the so-called 'thermodynamic limit', which is the theoretical maximum efficiency of converting sunlight to electricity. This paves the way toward an industrially deployable, new generation of perovskite photovoltaics."
Michael Saliba | Taisuke Matsui | Konrad Domanski | Ji-Youn Seo | Amita Ummadisingu | Shaik M. Zakeeruddin | Juan-Pablo Correa-Baena | Wolfgang R. Tress | Antonio Abate | Anders Hagfeldt | Michael GrätzelDOI: 10.1126/science.aah5557
All of the cations currently used in perovskite solar cells (PSCs) abide by the tolerance factor for incorporation into the lattice. We show that the small and oxidation-stable Rb+ can be embedded into a “cation cascade” to create perovskite materials with excellent material properties. We achieved stabilized efficiencies of up to 21.6% (average value: 20.2%) on small areas (and a stabilized 19.0% on a 0.5 cm2 cell) as well as an electroluminescence of 3.8%. The open-circuit voltage of 1.24 volts at a band gap of 1.63 electron volts leads to loss-in-potential of 0.39 V, versus 0.4 V for commercial silicon cells. Polymer-coated cells maintained 95% of their initial performance at 85°C for 500 hours under full solar illumination and maximum power point tracking.