Efficient Light-Emitting Diodes Based on Nanocrystalline Perovskite in

Feb 24, 2015 - Citation data is made available by participants in Crossref's Cited-by Linking service. ..... Yeob Lee , Young-Hyun Song , Eun Kyung Ji...
0 downloads 13 Views 3MB Size
Subscriber access provided by YORK UNIV

Communication

Efficient Light-Emitting Diodes based on NanoCrystalline Perovskite in a Dielectric Polymer Matrix Guangru Li, Zhi-Kuang Tan, Dawei Di, May Ling Lai, Lang Jiang, Jonathan Hua-wei Lim, Richard H. Friend, and Neil C. Greenham Nano Lett., Just Accepted Manuscript • DOI: 10.1021/acs.nanolett.5b00235 • Publication Date (Web): 24 Feb 2015 Downloaded from http://pubs.acs.org on March 2, 2015

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

Nano Letters is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 16

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Nano Letters

Efficient Light-Emitting Diodes based on NanoCrystalline Perovskite in a Dielectric Polymer Matrix Guangru Li, Zhi-Kuang Tan, Dawei Di, May Ling Lai, Lang Jiang, Jonathan Hua-Wei Lim, Richard H. Friend and Neil C. Greenham* Cavendish Laboratory, University of Cambridge, J. J. Thomson Avenue, Cambridge CB3 0HE, UK

ABSTRACT Electroluminescence in light-emitting devices relies on the encounter and radiative recombination of electrons and holes in the emissive layer. In organometal halide perovskite light-emitting diodes, poor film formation creates electrical shunting paths, where injected charge carriers bypass the perovskite emitter, leading to a loss in electroluminescence yield.

ACS Paragon Plus Environment

1

Nano Letters

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 2 of 16

Here, we report a solution-processing method to block electrical shunts and thereby enhance electroluminescence quantum efficiency in perovskite devices. In this method, a blend of perovskite and a polyimide precursor dielectric (PIP) is solution-deposited to form perovskite nanocrystals in a thin-film matrix of PIP. The PIP forms a pinhole-free charge-blocking layer, while still allowing the embedded perovskite crystals to form electrical contact with the electronand hole-injection layers. This modified structure reduces non-radiative current losses and improves quantum efficiency by 2 orders of magnitude, giving an external quantum efficiency (EQE) of 1.2%. This simple technique provides an alternative route to circumvent film formation problems in perovskite optoelectronics, and offers the possibility of flexible and highperformance light-emitting displays.

Keywords: perovskite light emitting diode, perovskite-polymer blend, perovskite nanocrystals, perovskite morphology

ACS Paragon Plus Environment

2

Page 3 of 16

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Nano Letters

Solution processing of luminescent semiconductors presents a particularly attractive option for the low-cost fabrication of light-emitting devices.1-4 Recent work on high-efficiency organometal halide perovskite photovoltaics has shown these materials to possess both the remarkable qualities of traditional semiconductors and the facile processability of organic semiconductors.5-9 A new report on perovskite nanoparticles has further shown these materials to possess high photoluminescence quantum yield.10 The perovskite materials also benefit from low cost and earth-abundance, and can be deposited at low temperatures under ambient conditions. More recently, bright and color-controlled electroluminescence was reported in perovskite lightemitting diodes (PeLED), thereby opening up a potential range of display and lighting applications for these materials.11,12 However, the quantum efficiencies in these PeLED devices remain modest due to difficulties in the formation of uniform thin films. Light emission occurs when injected electrons and holes meet in the perovskite layer and recombine radiatively. However, it is easy for injected charges to bypass the perovskite layer through pinholes in the thin films, leading to non-radiative current losses and a lower efficiency. Difficulties in the formation of uniform and pinhole-free perovskite films are well known, due to the crystalline nature of the material. This problem is further exacerbated by the sublimation of excess methylammonium halide precursor during thermal annealing, thereby leaving voids in the perovskite layer. New techniques involving sequential or vapor deposition of perovskite precursors have been developed to improve film formation in the thick perovskite layers used for

ACS Paragon Plus Environment

3

Nano Letters

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 4 of 16

photovoltaics,7,13 but these techniques do not completely eliminate pin-holes, and hence are not a sufficient solution for the ultra-thin (