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Functional Nanostructured Materials (including low-D carbon)
High Color Rendering Index White-Light Emission from UVDriven LEDs Based on Single Luminescent Materials: TwoDimensional Perovskites (C6H5C2H4NH3)2PbBrxCl4-x Shuming Yang, Zhenghuan Lin, Jingwei Wang, Yunxiang Chen, Zhengde Liu, E Yang, Jian Zhang, and Qidan Ling ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.8b00048 • Publication Date (Web): 18 Apr 2018 Downloaded from http://pubs.acs.org on April 18, 2018
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ACS Applied Materials & Interfaces
High Color Rendering Index White-Light Emission from UV-Driven LEDs Based on Single Luminescent Materials: Two-Dimensional Perovskites (C6H5C2H4NH3)2PbBrxCl4-x Shuming Yang†, Zhenghuan Lin*†, Jingwei Wang†, Yunxiang Chen†, Zhengde Liu†, E yang†, Jian Zhang*‡ and Qidan Ling*† † Fujian Key Laboratory of Polymer Materials, College of Chemistry and Materials Science, Fujian Normal University, Fuzhou 350007, China. ‡ Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002, P. R. China.
KEYWORDS: 2D perovskite, white-light emission, LED, mixed halide, single-component
ABSTRACT: Two-dimensional (2D) white light-emitting hybrid perovskites (WHPs) are promising active materials for the single-component white light-emitting diodes (WLEDs) driven by UV. However, the reported WHPs exhibit low quantum yields (≤9 %) and low color rendering index (CRI) values less than 85, which does not satisfy the demand of solid-state lighting applications. In this work, we report a series of mixed-halide 2D layered WHPs (C6H5C2H4NH3)2PbBrxCl4-x (0＜x＜4) obtained from the phenethylammonium cation. Unlike the reported WHPs including (C6H5C2H4NH3)2PbCl4, the mixed-halide perovskites display morphology-dependent white emission for the different extent of self-absorption.
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Additionally, the amount of Br imposes huge influence on the photophysical properties of the mixed-halide WHPs. With the increasing content of Br, the quantum yields of the WHPs increase gradually from 0.2 % to 16.9%, accompanied by tunable color temperature ranging from 4000 K (“warm” white light) to 7000 K (“cold” white light). When applied in the WLEDs, the mixed-halide perovskite powders exhibit tunable white electroluminescent emission with very high CRI of 87-91.
1. INTRODUCTION Solid-state illumination from the white light-emitting diodes (WLEDs) has significant advantages, such as higher efficiency, lower energy consumption and safer application, relative to traditional light sources.1-2 Thus, WLEDs will replace the fluorescent lamps and become mainstream light sources in recent ten years. There are mainly two kinds of methods to produce white light for WLEDs: blue light-emitting diodes (LEDs) excited a yellow phosphor3-6 and an ultraviolet LED excited red, green and blue phosphors.7-9 However, the white emission obtained by the former has low color rendition index for the narrow emission band.7, 9-10 The WLEDs fabricated by the latter cause efficiency losses and poor color purity for the self-absorption and different degradation rates of each phosphor.9 Phosphors used in WLEDs usually consist of metal oxides or metal nitrides doped by rare-earth ions, such as Eu3+ or Ce3+, which are synthesized in very high temperature.9, 11 Consequently, to design new easily-synthesized single white light-emitting materials with broadband emission excited by UV is important for WLEDs in the application of solid-state lighting.12-15 It is a great challenge to obtain such single-component broadband white-light-emitting materials, because there are only few successful examples applied in WLEDs.16-18 Hybrid
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ACS Applied Materials & Interfaces
organic-inorganic halide perovskites have attracted wide interest in the fields of photovoltaic and optoelectronic devices for their high performance.19-23 Thereinto, two-dimensional (2D) layered perovskites exhibit great potential in the optoelectronic application, due to the high stability and luminescent efficiency, as well as flexible crystalline structure originated from the tolerance for versatile organic cations.24-28 Recently, different types of 2D layered perovskites, including single-layered and three-layered, (100) and (110), Pb-Cl and Pb-Br structure, were found to be white-light emitter.29-36 Their broadband emission is not ascribed to deep trap states at surface sites, like nanometer-scale CdSe crystals,37 and presumably attributed to the self-trapped exciton resulted from the strong electron-phonon coupling in a deformable lattice. For example, Karunadasa et al.10d, perovskites
based
on
10e
reported two family of layered
N-methyl-ethane-1,2-diammonium
2,2’-(ethylenedioxy)bis(ethylammonium)
(EDBE)
cations,
(N-MEDA)
and
respectively.
The
photoluminescent quantum yields (Φp) of the first family were 0.5-1.5%, while it was improved to 9% in the second family. Very recently, Mathews et al.38 reported a phenethylammonium-based 2D hybrid lead chloride perovskite (C6H5C2H4NH3)2PbCl4 (PEPC) emitting morphology-independent stable white light with a high color rendering index (CRI) of 84, a CIE coordinated of (0.37, 0.42), a CCT of 4426 K. However, the Φp of PEPC in various forms was found to be
