TY  - JOUR
A1  - Zu, Fengshuo
A1  - Schultz, Thorsten
A1  - Wolff, Christian Michael
A1  - Shin, Dongguen
A1  - Frohloff, Lennart
A1  - Neher, Dieter
A1  - Amsalem, Patrick
A1  - Koch, Norbert
T1  - Position-locking of volatile reaction products by atmosphere and capping layers slows down photodecomposition of methylammonium lead triiodide perovskite
JF  - RSC Advances
N2  - The remarkable progress of metal halide perovskites in photovoltaics has led to the power conversion efficiency approaching 26%. However, practical applications of perovskite-based solar cells are challenged by the stability issues, of which the most critical one is photo-induced degradation. Bare CH3NH3PbI3 perovskite films are known to decompose rapidly, with methylammonium and iodine as volatile species and residual solid PbI2 and metallic Pb, under vacuum under white light illumination, on the timescale of minutes. We find, in agreement with previous work, that the degradation is non-uniform and proceeds predominantly from the surface, and that illumination under N-2 and ambient air (relative humidity 20%) does not induce substantial degradation even after several hours. Yet, in all cases the release of iodine from the perovskite surface is directly identified by X-ray photoelectron spectroscopy. This goes in hand with a loss of organic cations and the formation of metallic Pb. When CH3NH3PbI3 films are covered with a few nm thick organic capping layer, either charge selective or non-selective, the rapid photodecomposition process under ultrahigh vacuum is reduced by more than one order of magnitude, and becomes similar in timescale to that under N-2 or air. We conclude that the light-induced decomposition reaction of CH3NH3PbI3, leading to volatile methylammonium and iodine, is largely reversible as long as these products are restrained from leaving the surface. This is readily achieved by ambient atmospheric pressure, as well as a thin organic capping layer even under ultrahigh vacuum. In addition to explaining the impact of gas pressure on the stability of this perovskite, our results indicate that covalently "locking" the position of perovskite components at the surface or an interface should enhance the overall photostability.
Y1  - 2020
U6  - https://doi.org/10.1039/d0ra03572f
SN  - 2046-2069
VL  - 10
IS  - 30
SP  - 17534
EP  - 17542
PB  - Royal Society of Chemistry
CY  - Cambridge
ER  - 
TY  - JOUR
A1  - Warby, Jonathan
A1  - Zu, Fengshuo
A1  - Zeiske, Stefan
A1  - Gutierrez-Partida, Emilio
A1  - Frohloff, Lennart
A1  - Kahmann, Simon
A1  - Frohna, Kyle
A1  - Mosconi, Edoardo
A1  - Radicchi, Eros
A1  - Lang, Felix
A1  - Shah, Sahil
A1  - Pena-Camargo, Francisco
A1  - Hempel, Hannes
A1  - Unold, Thomas
A1  - Koch, Norbert
A1  - Armin, Ardalan
A1  - De Angelis, Filippo
A1  - Stranks, Samuel D.
A1  - Neher, Dieter
A1  - Stolterfoht, Martin
T1  - Understanding performance limiting interfacial recombination in pin Perovskite solar cells
JF  - Advanced energy materials
N2  - Perovskite semiconductors are an attractive option to overcome the limitations of established silicon based photovoltaic (PV) technologies due to their exceptional opto-electronic properties and their successful integration into multijunction cells. However, the performance of single- and multijunction cells is largely limited by significant nonradiative recombination at the perovskite/organic electron transport layer junctions. In this work, the cause of interfacial recombination at the perovskite/C-60 interface is revealed via a combination of photoluminescence, photoelectron spectroscopy, and first-principle numerical simulations. It is found that the most significant contribution to the total C-60-induced recombination loss occurs within the first monolayer of C-60, rather than in the bulk of C-60 or at the perovskite surface. The experiments show that the C-60 molecules act as deep trap states when in direct contact with the perovskite. It is further demonstrated that by reducing the surface coverage of C-60, the radiative efficiency of the bare perovskite layer can be retained. The findings of this work pave the way toward overcoming one of the most critical remaining performance losses in perovskite solar cells.
KW  - C60
KW  - defects
KW  - interface recombination
KW  - loss mechanisms
KW  - perovskites
KW  - solar cells
Y1  - 2022
U6  - https://doi.org/10.1002/aenm.202103567
SN  - 1614-6832
SN  - 1614-6840
VL  - 12
IS  - 12
PB  - Wiley-VCH
CY  - Weinheim
ER  -