Halide segregation versus interfacial recombination in bromide-rich wide-gap perovskite solar cells}
Francisco Peña-Camargo a, Pietro Caprioglio a b, Fengshuo Zu c d, Emilio Gutierrez-Partida a, Christian M. Wolff a, Kai Brinkmann e, Steve Albrecht b, Thomas Riedl e, Norbert Koch b, Dieter Neher a, Martin Stolterfoht a
a Institute of Physics and Astronomy, University of Potsdam, Karl-Liebknecht-Str. 24-25, D-14476 Potsdam-Golm, Germany.
b Young Investigator Group Perovskite Tandem Solar Cells, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Kekuléstraße 5, 12489 Berlin, Germany
c Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, 12489 Berlin, Germany
d Institut für Physik & IRIS Adlershof, Humboldt-Universitat zu Berlin, 12489 Berlin, Germany
e Institute of Electronic Devices, University of Wuppertal, Rainer-Gruenter-Str 21, 42119 Wuppertal, Germany
Online School
Proceedings of Online School on Fundamentals of Emerging Solar Cells (PVSCHOOL)
Online, Spain, 2021 February 10th - 12th
Organizers: Bruno Ehrler, Thomas Kirchartz and Elizabeth von Hauff
Poster, Francisco Peña-Camargo, 013
Publication date: 29th January 2021

Perovskites offer exciting opportunities to realise efficient multi-junction photovoltaic devices. This requires high-VOC and often Br-rich perovskites which currently suffer from halide segregation. Here, we study triple-cation perovskite cells over a wide bandgap-range (~ 1.5-1.9eV). While all wide-gap cells (≥1.69eV) experience rapid phase segregation under illumination, the electroluminescence spectra are less affected by this process. The measurements reveal a low radiative efficiency of the mixed halide phase which explains the VOC-losses with increasing Br-content. Photoluminescence measurements on non-segregated partial cell stacks demonstrate that both transport layer (PTAA and C60) induce significant non-radiative interfacial recombination, especially in Br-rich (>30%) samples. Therefore, the presence of the segregated iodide-rich domains is not directly responsible for the VOC-losses. Moreover, LiF can only improve the VOC of cells that are primarily limited by the n-interface (≤1.75eV) resulting in 20% efficient 1.7eV bandgap cells. However, a simultaneous optimization of the p-interface is necessary to further advance larger bandgap (≥1.75eV) pin-type cells.

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