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High Chloride Doping Levels Stabilize the Perovskite Phase of Cesium Lead Iodide
Journal article   Peer reviewed

High Chloride Doping Levels Stabilize the Perovskite Phase of Cesium Lead Iodide

Subham Dastidar, David A. Egger, Liang Z. Tan, Samuel B. Cromer, Andrew D. Dillon, Shi Liu, Leeor Kronik, Andrew M. Rappe and Aaron T. Fafarman
Nano letters, v 16(6), pp 3563-3570
01 Jun 2016
PMID: 27135266

Abstract

Chemistry Chemistry, Multidisciplinary Chemistry, Physical Materials Science Materials Science, Multidisciplinary Nanoscience & Nanotechnology Physical Sciences Physics Physics, Applied Physics, Condensed Matter Science & Technology Science & Technology - Other Topics Technology
Cesium lead iodide possesses an excellent combination of band gap and absorption coefficient for photovoltaic applications in its perovskite phase. However, this is not its equilibrium structure under ambient conditions. In air, at ambient temperature it rapidly transforms to a nonfunctional, so-called yellow phase. Here we show that chloride doping, particularly at levels near the solubility limit for chloride in a cesium lead iodide host, provides a new approach to stabilizing the functional perovskite phase. In order to achieve high doping levels, we first co-deposit colloidal nanocrystals of pure cesium lead chloride and cesium lead iodide, thereby ensuring nanometer-scale mixing even at compositions that potentially exceed the bulk miscibility of the two phases. The resulting nanocrystal solid is subsequently fused into a polycrystalline thin film by chemically induced, room-temperature sintering. Spectroscopy and X-ray diffraction indicate that the chloride is further dispersed during sintering and a polycrystalline mixed phase is formed. Using density functional theory (DFT) methods in conjunction with nudged elastic band techniques, low-energy pathways for interstitial chlorine diffusion into a majority-iodide lattice were identified, consistent with the facile diffusion and fast halide exchange reactions observed. By comparison to DFT-calculated values (with the PBE exchange-correlation functional), the relative change in band gap and the lattice contraction are shown to be consistent with a Cl/I ratio of a few percent in the mixed phase. At these incorporation levels, the half-life of the functional perovskite phase in a humid atmosphere increases by more than an order of magnitude.

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Collaboration types
Domestic collaboration
International collaboration
Web of Science research areas
Chemistry, Multidisciplinary
Chemistry, Physical
Materials Science, Multidisciplinary
Nanoscience & Nanotechnology
Physics, Applied
Physics, Condensed Matter
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