Mixed-Halide Perovskites with Stabilized Bandgaps - Nano Letters

Oct 2, 2017 - ... films; Figure S7: Cross-sectional STEM image and EDS mapping of fresh ... Figure S15: Statistics of VOC versus absorption edge based...
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Mixed-halide perovskites with stabilized bandgaps Zhengguo Xiao, Lianfeng Zhao, Nhu Tran, YunHui Lisa Lin, Scott H. Silver, Ross A. Kerner, Nan Yao, Antoine Kahn, Gregory D. Scholes, and Barry P. Rand Nano Lett., Just Accepted Manuscript • DOI: 10.1021/acs.nanolett.7b03179 • Publication Date (Web): 02 Oct 2017 Downloaded from http://pubs.acs.org on October 3, 2017

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Nano Letters

Mixed-halide perovskites with stabilized bandgaps Zhengguo Xiao1, Lianfeng Zhao1, Nhu L. Tran2, Yunhui (Lisa) Lin1, Scott H. Silver1, Ross A. Kerner1, Nan Yao3, Antoine Kahn1, Gregory D. Scholes2, Barry P. Rand1,4*.

1

Department of Electrical Engineering, Princeton University, Princeton, New Jersey 08544,

United States 2

Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States

3

Princeton Institute for Science and Technology of Materials, Princeton University, Princeton,

New Jersey 08544, United States 4

Andlinger Center for Energy and the Environment, Princeton University, Princeton, New Jersey

08544, United States

KEYWORDS: Mixed-halide perovskite, halide migration, phase separation, LEDs, solar cells.

ABSTRACT: One merit of organic-inorganic hybrid perovskites is their tunable bandgap by adjusting the halide stoichiometry, an aspect critical to their application in tandem solar cells, wavelength-tunable light emitting diodes (LEDs), and lasers. However, the phase separation of mixed-halide perovskites caused by light or applied bias results in undesirable recombination at iodide-rich domains, meaning open-circuit voltage (VOC) pinning in solar cells and infrared emission in LEDs. Here, we report an approach to suppress halide redistribution by selfassembled long-chain organic ammonium capping layers at nanometer-sized grain surfaces.

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Using the stable mixed-halide perovskite films, we are able to fabricate efficient and wavelengthtunable perovskite LEDs from infrared to green with high external quantum efficiencies of up to 5%, as well as linearly tuned VOC from 1.05 V to 1.45 V in solar cells.

The performances of metal halide perovskites-based devices have experienced consistent and rapid progress recently, both for solar cells1-3 and light emitting diodes (LEDs)4-10. Mixedhalide perovskites are particularly attractive, as they allow for bandgap tuning, necessary for making tandem solar cells and wavelength tunable LEDs and lasers11-16. However, mixed-halide perovskites such as methylammonium (MA) or formamidinium (FA) lead iodide/bromide (MAPb(I1-xBrx)3 or FAPb(I1-xBrx)3), have phase instability issues originating from differences in crystal structure between the I- and Br-perovskites17. This results in de-mixing of the halides for mid x values (0.2