Click image for HiRes
Abstract
Integrating metal halide perovskite top cells with bottom cells formed by crystalline silicon or low band gap perovskites into monolithic tandem or triple junction devices has recently attracted increased attention due to the high efficiency potential and application relevance of these cell architectures. Here we present our recent results on monolithic tandem combinations of perovskite top-cells with crystalline silicon, and Sn-Pb perovskites as well as tandem relevant aspects of perovskite single junction solar cells.
We have shown that self-assembled monolayers (SAM) could be implemented as appropriate hole-selective contacts. The implementation of advanced SAM molecules enabled a further reduction in non-radiative recombination losses resulting in high open-circuit voltages and fill factors. In addition, we demonstrated that a perovskite surface treatment strongly reduces interface recombination and improves the band alignment with the C60 electron-transporting material. With these modifications, a new world record for perovskite/silicon tandem solar cells at 32.5% efficiency was realized in 2022.
Further work on replacing the C60 electron-transporting material enabled us to identify a new class of materials with a Carborane core and conjugated functional groups: mCB-FMN. This new material shows superior material properties compared with C60 contacts and might open the way to more stable solar cell configurations.
Driven by potential stability and scaling advantages, we have gained interesting insights into the crystallization of perovskite absorber films using seed layers to improve film quality during co-evaporation. We found through precise measurements of the underlying SAM morphology and the initial growth of the perovskite during co-evaporation using synchrotron-based methods that high-quality absorber films can be favourably obtained with seeding. This improvement resulted in a perovskite-silicon tandem solar cell with an efficiency of 30.3% with conformal deposition of the perovskite on micrometer-sized random pyramids using co-evaporation.
Very recent results on all-perovskite triple junction solar cells are presented for which space applications might become relevant. Transient measurements show that carrier extraction is impeded for SAM-based Sn/Pb low band gap solar cells containing typical processing additives. The experiments further reveal the unintended relocation of SAMs to the top surface of the perovskite layer. Guided by these insights, we demonstrate that a graphene oxide/SAM bilayer concurrently mitigates electronic and ionic losses, enabling all perovskite triple junctions with 27.3% efficiency and one of the highest levels of operational stability reported to date.
Finally, the main scientific and technological challenges and empirical efficiency limits as well as operational stability will be highlighted.
Click here to see all available video seminars.
Click here to go to the SPREE HOMEPAGE.
Brief Bio
Steve Albrecht is a full Professor at Technical University (TU) Berlin, Faculty IV, Electrical Engineering and Computer Science and Head of the Department for Perovskite Tandem Solar Cells at Helmholtz-Zentrum Berlin (HZB). He is currently the speaker of the HySPRINT Photovoltaics Lab at HZB, he was very recently awarded with a Feodor-Lynen Fellowship from the Alexander von Humboldt Foundation and he is a visiting professorial fellow at UNSW.
He received his PhD in physics from the University of Potsdam for his work on understanding the conversion of photon to collected charges organic solar cells in 2015. For his PhD he was awarded with the Carl-Ramsauer-Prize of the Physikalische Gesellschaft zu Berlin and the Young Researcher Prize of the Leibniz-Kolleg Potsdam. After PhD he started as Postdoc at HZB and in 2016 he established a young investigator research group and in 2017 the HySPRINT Innovation Lab. In 2018, he was granted with the apple of inspiration award by the Slovenian President followed by the Karl-Scheel-Preis of the Physikalische Gesellschaft zu Berlin and the Berliner Wissenschaftspreis in the category young scientists for his work on perovskite-based tandem solar cells. Since June 2022, he is heading the department for perovskite tandem solar cells at HZB and since August 2022 he was promoted from Junior- to Full Professor at TU Berlin.
He and his team developed various high efficiency hybrid tandem solar cells such as organic/amorphous Silicon and Perovskite/crystalline Silicon tandem solar cells. In recent years, his group enabled various certified efficiency records for e.g. Perovskite/Silicon tandem solar cells such as 29.15%, 29.8%, and 32.5% in 2020, 2021, and 2022, respectively.
