TY  - JOUR
A1  - Cappel, Ute B.
A1  - Svanstrom, Sebastian
A1  - Lanzilotto, Valeria
A1  - Johansson, Fredrik O. L.
A1  - Aitola, Kerttu
A1  - Philippe, Bertrand
A1  - Giangrisostomi, Erika
A1  - Ovsyannikov, Ruslan
A1  - Leitner, Torsten
A1  - Föhlisch, Alexander
A1  - Svensson, Svante
A1  - Martensson, Nils
A1  - Boschloo, Gerrit
A1  - Lindblad, Andreas
A1  - Rensmo, Hakan
T1  - Partially Reversible Photoinduced Chemical Changes in a Mixed-Ion Perovskite Material for Solar Cells
JF  - ACS applied materials & interfaces
N2  - Metal halide perovskites have emerged as materials of high interest for solar energy-to-electricity conversion, and in particular, the use of mixed-ion structures has led to high power conversion efficiencies and improved stability. For this reason, it is important to develop means to obtain atomic level understanding of the photoinduced behavior of these materials including processes such as photoinduced phase separation and ion migration. In this paper, we implement a new methodology combining visible laser illumination of a mixed-ion perovskite ((FAP-bI(3))(0.85)(MAPbBr(3))(0.15)) with the element specificity and chemical sensitivity of core-level photoelectron spectroscopy. By carrying out measurements at a synchrotron beamline optimized for low X-ray fluxes, we are able to avoid sample changes due to X-ray illumination and are therefore able to monitor what sample changes are induced by visible illumination only. We find that laser illumination causes partially reversible chemistry in the surface region, including enrichment of bromide at the surface, which could be related to a phase separation into bromide- and iodide-rich phases. We also observe a partially reversible formation of metallic lead in the perovskite structure. These processes occur on the time scale of minutes during illumination. The presented methodology has a large potential for understanding light-induced chemistry in photoactive materials and could specifically be extended to systematically study the impact of morphology and composition on the photostability of metal halide perovskites.
KW  - photoelectron spectroscopy
KW  - laser illumination
KW  - lead halide perovskite
KW  - ion migration
KW  - phase separation
KW  - stability
Y1  - 2017
U6  - https://doi.org/10.1021/acsami.7b10643
SN  - 1944-8244
VL  - 9
SP  - 34970
EP  - 34978
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Fondell, Mattis
A1  - Eckert, Sebastian
A1  - Jay, Raphael Martin
A1  - Weniger, Christian
A1  - Quevedo, Wilson
A1  - Niskanen, Johannes
A1  - Kennedy, Brian
A1  - Sorgenfrei, Nomi
A1  - Schick, Daniel
A1  - Giangrisostomi, Erika
A1  - Ovsyannikov, Ruslan
A1  - Adamczyk, Katrin
A1  - Huse, Nils
A1  - Wernet, Philippe
A1  - Mitzner, Rolf
A1  - Föhlisch, Alexander
T1  - Time-resolved soft X-ray absorption spectroscopy in transmission mode on liquids at MHz repetition rates
JF  - Structural dynamics
N2  - We present a setup combining a liquid flatjet sample delivery and a MHz laser system for time-resolved soft X-ray absorption measurements of liquid samples at the high brilliance undulator beamline UE52-SGM at Bessy II yielding unprecedented statistics in this spectral range. We demonstrate that the efficient detection of transient absorption changes in transmission mode enables the identification of photoexcited species in dilute samples. With iron(II)-trisbipyridine in aqueous solution as a benchmark system, we present absorption measurements at various edges in the soft X-ray regime. In combination with the wavelength tunability of the laser system, the set-up opens up opportunities to study the photochemistry of many systems at low concentrations, relevant to materials sciences, chemistry, and biology. (C) 2017 Author(s).
Y1  - 2017
U6  - https://doi.org/10.1063/1.4993755
SN  - 2329-7778
VL  - 4
PB  - American Institute of Physics
CY  - Melville
ER  -