Perovskite/Si tandem solar cells with 30% efficiency

Short Bio:

Dr. Lars Korte is deputy group leader of the Young Investigator Group Perovskite Tandem Solar Cells at Helmholtz-Zentrum Berlin (HZB). He studied physics in Göttingen, Germany, then went to Laboratoire de Chimie Métallurgique des Terres Rares, CNRS, France, as a visiting researcher. He carried out his PhD research at Hahn-Meitner-Institut Berlin and obtained his PhD in physics from U Marburg in 2006. Lars is permanent staff member at HZB since 2010. As deputy head of HZB’s Institute for Silicon Photovoltaics, he led the research on amorphous/silicon heterojunction solar cells. Since 2015, his work is focusing on perovskite/silicon tandem cells. Lars’ research interests include the electronic properties of thin films and heterointerfaces; materials and device characterization with photoelectron spectroscopy (XPS, UPS, near-UV) and photoelectrical methods; high efficiency silicon heterojunction solar cells and perovskite-/silicon-based tandem cells. He is author/co-author of more than 150 publications, with an h-index of 39. Lars is an appointed lecturer at Technical University Berlin’s faculty Electrical Engineering.

Perovskite/Si tandem solar cells with 30% efficiency

Lars Korte^1,*, Eike Köhnen¹, Bor Li¹, Silvia Mariotti¹, Marcel Roß¹, Kári Sveinbjörnsson¹, Philipp Tockhorn¹, Philipp Wagner¹, Fengjiu Yang¹, Ke Xu¹, Christiane Becker¹, Eva Unger^1,2, Bernd Stannowski¹, Steve Albrecht^1,3

Integrating metal halide perovskite top cells with crystalline silicon, CIGS, or low band gap perovskite bottom cells into monolithic tandem devices has recently attracted increased attention due to the high efficiency potential of these cell architectures. To further increase the performance of these fascinating tandem solar cells to a level of predicted efficiency limits well above 30%, optical and electrical optimizations as well as a detailed device understanding of these advanced tandem architectures need to be developed. 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.

Recently we have shown that self-assembled monolayers (SAM) could be implemented as appropriate hole selective contacts. The implementation of a new generation of SAM molecules enabled further reduction of non-radiative recombination losses with high open circuit voltages and fill factors. By fine-tuning the SAM molecular structure even further, the photostability of perovskite composition with tandem-ideal band gaps of 1.68 eV could be enhanced by reduction of defect density and fast hole extraction. That enabled a certified power conversion efficiency for perovskite/silicon tandems at 29.15% [1]. By optical optimizations, we could improve this value to 29.80% recently [2]. Pathways to further improvements through interface engineering using polar molecules such as piperazinium iodide (PI) [3] will also be discussed.

Furthermore, we recently demonstrated first so-called 3-terminal perovskite/silicon tandem cells, i.e. monolithically integrated devices with an overall similar layer stack but featuring an additional contact on the rear side [4]. The advantages of this device design under varying illumination conditions will be shown. 

In addition to the experimental material and device development, also main scientific and technological challenges, and empirical efficiency limits [5] as well as advanced analysis methods will be discussed for perovskite based tandem solar cells. Finally, first results for upscaling of these industrially relevant tandem solar cells by thermal evaporation and slot-die coating will be shown.

[1] Al-Ashouri A, Köhnen E, Li B, Magomedov A, Hempel H, Caprioglio P, et al. Monolithic perovskite/silicon tandem solar cell with >29% efficiency by enhanced hole extraction. Science. 2020 Dec 11;370(6522):1300–9.

[2] Tockhorn P, Sutter J, et al. Nano-optical designs for high-efficiency monolithic perovskite–silicon tandem solar cells, Nature Nanotechnology, accepted (2022), DOI: 10.1038/s41565-022-01228-8.

[3] Mariotti S, Köhnne E, Scheler S, Korte L, Albrecht S, et al., manuscript in preparation.

[4] Tockhorn P, Wagner P, Kegelmann L, Stang JC, Mews M, Albrecht S, et al. Three-Terminal Perovskite/Silicon Tandem Solar Cells with Top and Interdigitated Rear Contacts. ACS Appl Energy Mater. 2020 Jan 15;3:1381–92.

[5] 1. Jošt M, Kegelmann L, Korte L, Albrecht S. Monolithic Perovskite Tandem Solar Cells: A Review of the Present Status and Advanced Characterization Methods Toward 30% Efficiency. Advanced Energy Materials. 2020;10(26):1904102.

Host: Prof. Yabing Qi, Energy Materials and Surface Sciences Unit (Qi unit)