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A Highly Emissive Surface Layer in Mixed-Halide Multication Perovskites

Andaji-Garmaroudi, Z; Abdi-Jalebi, M; Guo, D; Macpherson, S; Sadhanala, A; Tennyson, EM; Ruggeri, E; ... Stranks, SD; + view all (2019) A Highly Emissive Surface Layer in Mixed-Halide Multication Perovskites. Advanced Materials , 31 (42) , Article 1902374. 10.1002/adma.201902374. Green open access

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Abstract

Mixed‐halide lead perovskites have attracted significant attention in the field of photovoltaics and other optoelectronic applications due to their promising bandgap tunability and device performance. Here, the changes in photoluminescence and photoconductance of solution‐processed triple‐cation mixed‐halide (Cs_{0.06MA}_{0.15}FA_{0.79})Pb(Br_{0.4}I_{0.6})_{3} perovskite films (MA: methylammonium, FA: formamidinium) are studied under solar‐equivalent illumination. It is found that the illumination leads to localized surface sites of iodide‐rich perovskite intermixed with passivating PbI2 material. Time‐ and spectrally resolved photoluminescence measurements reveal that photoexcited charges efficiently transfer to the passivated iodide‐rich perovskite surface layer, leading to high local carrier densities on these sites. The carriers on this surface layer therefore recombine with a high radiative efficiency, with the photoluminescence quantum efficiency of the film under solar excitation densities increasing from 3% to over 45%. At higher excitation densities, nonradiative Auger recombination starts to dominate due to the extremely high concentration of charges on the surface layer. This work reveals new insight into phase segregation of mixed‐halide mixed‐cation perovskites, as well as routes to highly luminescent films by controlling charge density and transfer in novel device structures.

Type: Article
Title: A Highly Emissive Surface Layer in Mixed-Halide Multication Perovskites
Open access status: An open access version is available from UCL Discovery
DOI: 10.1002/adma.201902374
Publisher version: https://doi.org/10.1002/adma.201902374
Language: English
Additional information: © 2019 The Authors. Published by WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim. This is an open access article under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/).
Keywords: halide perovskites, luminescence, passivation, photoinduced ion migration, time-resolved spectroscopy
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > MAPS Faculty Office
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > MAPS Faculty Office > Institute for Materials Discovery
URI: https://discovery.ucl.ac.uk/id/eprint/10092526
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