Lead Halide Post‐Perovskite‐Type Chains for High‐Efficiency White‐Light Emission

Abstract

Hybrid metal halides containing perovskite layers have recently shown great potential for applications in solar cells and light‐emitting diodes. Such compounds exhibit quantum confinement effects leading to tunable optical and electronic properties. Thus, broadband white‐light emission has been observed from diverse metal halides and, owing to high color rendering index, high thermal stability, and low‐temperature solution processability, these materials have attracted interest for application in solid‐state lighting. However, the reported quantum yields for white photoluminescence (PLQY) remain low (i.e., in the range 0.5–9%) and no approach has shown to successfully increase the intensity of this emission. Here, it is demonstrated that the quantum efficiencies of hybrid metal halides can be greatly enhanced if they contain a polymorph of the [PbX4]2− perovskite‐type layers: the [PbX4]2− post‐perovskite‐type chains showing a PLQY of 45%. Different piperazines lead to a hybrid lead halide with either perovskite layers or post‐perovskite chains influencing strongly the presence of self‐trapped states for excitons. It is anticipated that this family of hybrid lead halide materials could enhance all the properties requiring the stabilization of trapped excitons.

Doped Lead Halide White Phosphors for Very High Efficiency and Ultra‐High Color Rendering

“…[12,13] Recently,low-dimensional hybrid metal halides including hybrid perovskites have attracted agreat attention. [14][15][16][17] Their emissions can be extremely broad owing to exciton selftrapping,asoriginally reported by Nagami et al for ahybrid lead iodide. [18,19] Such emission offers rich opportunities for discovering single-phase white light emitters such as Cs 2 AgInCl 6 ,(EDBE)PbBr 4 (EDBE = 2,2'-(ethylenedioxy)bis(ethylammonium)), C 4 N 2 H 14 PbBr 4 ,( AMP)PbBr 5 .1/2H 2 O (AMP = 1-(2-aminoethyl)piperazine), or (TDMP)PbBr 4 (TDMP = trans-2,5-dimethylpiperaziniium).…”

“…In this context, we investigate the Mn doping of (TDMP)PbBr 4 ,w hich is ap ost-perovskite type compound we previously reported. [17] This material exhibits abroad emission at 510 nm, and we demonstrate that such Mn doping can lead to an ultra-high color rendering and high efficiency white light.…”

“…[38] The structure of (TDMP)PbBr 4 is shown in Figure 1a.T his onedimensional hybrid metal halide material is built of postperovskite-type chains,w hich are formed by the PbBr 6 4À octahedra connected with each other via edges and corners. [17] These chains are not ordered at long range.The powder X-ray diffraction (XRD) patterns,w hich are all identical to the simulated pattern, confirm the purity of the as prepared samples (Figure 1c). Furthermore,noshift of XRD peaks can be observed.…”

“…Concerning the photoluminescence properties of the materials,t he color rendering index of (TDMP)PbBr 4 reaches 77. [17] This value is relatively high, which can be used in daily lighting, but the lack of emission in the red region makes this phosphor limited for applications in which ultra-high color rendering is required (Figure 2d). However, upon Mn doping,t he emission at 640 nm increases and the CRI of the (TDMP)PbBr 4 :Mn is greatly enhanced (Supporting Information, Table S3).…”

“…[18,19] Such emission offers rich opportunities for discovering single-phase white light emitters such as Cs 2 AgInCl 6 ,(EDBE)PbBr 4 (EDBE = 2,2'-(ethylenedioxy)bis(ethylammonium)), C 4 N 2 H 14 PbBr 4 ,( AMP)PbBr 5 .1/2H 2 O (AMP = 1-(2-aminoethyl)piperazine), or (TDMP)PbBr 4 (TDMP = trans-2,5-dimethylpiperaziniium). [16,17,[20][21][22][23][24] Thecolor rendering index (CRI) of these materials can reach high values (ca. 70-90) owing to the broadband emission.…”