Efficient Dual-Band White-Light Emission with High Color Rendering from Zero-Dimensional Organic Copper Iodide

Abstract

Broad-band white-light emissions from organic–inorganic lead halide hybrids have attracted considerable attention in energy-saving solid-state lighting (SSL) applications. However, the toxicity of lead in these hybrids hinders their commercial prospects, and the low photoluminescence quantum yields (PLQYs) cannot meet the requirements for efficient lighting. Here, we report a highly efficient dual-band white-light emission from organic copper iodide, (C16H36N)­CuI2, which exhibits a high PLQY of 54.3% and excellent air stability. The single-crystalline (C16H36N)­CuI2 possesses a unique zero-dimensional (0D) structure, in which the isolated [Cu2I4]2– dimers are periodically embedded in the wide band gap organic framework of C16H36N+. This perfect 0D structure can cause significant quantum confinement and strong electron–phonon coupling, which contributes to efficient emissions from self-trapped excitons (STEs). Photophysical studies revealed the presence of two self-trapped emitting states in [Cu2I4]2– dimers, whose populations are highly sensitive to the temperature that governs the molecular environment for [Cu2I4]2– dimers and the thermal activation energy of STEs. An ultraviolet (UV) excited white light-emitting diode fabricated using this single-phase white-light emitter exhibits a high color rendering index (CRI) of 78. The new material provides a promising emitter, having a high PLQY and a high CRI simultaneously, for SSL and display applications.

Realizing Near-Unity Quantum Efficiency of Zero-Dimensional Antimony Halides through Metal Halide Structural Modulation

“…The integrated PL intensity and FWHM of (C 12 H 28 N) 2 SbCl 5 single crystals versus temperature are depicted in Figures S10 and e, respectively. The activation energy ( E a ) can be obtained by the following eq where I ( T ) and I 0 represent the emission intensity at T and 0 K and k B is the Boltzmann constant. The obtained E a = 205.26 meV is higher than that of three-dimensional metal halides, , which is beneficial to radiative recombination of localized excitons in [SbCl 5 ] 2– pyramids.…”

“…Zero-dimensional (0D) organic metal halides have triggered great interest and showed promising applications in solid-state lighting, , X-ray scintillation, , and remote thermography , because of their unique characteristics such as structural tunability, strong quantum confinement, negligible self-absorption, efficient photoluminescence (PL), and sensitive temperature-dependent radiative lifetimes. − In these hybrid materials, inorganic metal halide species are totally isolated from one another and wrapped by bulky organic cations, forming periodical structures. The spatial isolation results in weak electronic coupling between individual metal halide species, enabling the hybrid materials to exhibit intrinsic features of inorganic metal halide species .…”

“…The configuration of the metal halide species might be affected by metal ions, halide ions, and the A-site organic cations, giving rise to structure diversity and optical tunability of hybrid metal halides. For example, (1) although (C 9 NH 20 ) 2 MnBr 4 and (C 9 NH 20 ) 2 SnBr 4 use the same A-site organic cations (C 9 NH 20 ) + and halide ions Br – , the different metal ions Mn 2+ and Sn 2+ adopt tetrahedral [MnBr 4 ] 2– with green emission and seesaw-shaped [SnBr 4 ] 2– with deep-red emission, respectively; (2) the different halide ions also affect the configurations of metal halide species, which can be found in (C 16 H 36 N)­CuI 2 and (C 16 H 36 N)­CuBr 2 . (C 16 H 36 N)­CuI 2 single crystals possess isolated [Cu 2 I 4 ] 2– dimers and exhibit dual-band white-light emission, while (C 16 H 36 N)­CuBr 2 possesses isolated [CuBr 2 ] − quantum rods and displays sky-blue emission; (3) the A-site cations regulating the metal halide configurations can be observed in (C 9 NH 20 ) 2 SnBr 4 and (C 4 N 2 H 14 Br) 4 SnBr 6 .…”

Bulk Assembly of Zero-Dimensional Organic Copper Bromide Hybrid with Bright Self-Trapped Exciton Emission and High Antiwater Stability

“…However, the organic ligand of TBA + can work as a confining agent and a cation component, play an important role in confining the STE, and lead to the emission process. 42 Subsequently, the emission mechanism of (TBA)CuBr 2 was discussed in detail by temperature-dependent PL measurement in 78−298 K (Figure 4a), and the corresponding pseudocolor mapping of PL intensity, wavelength, and FWHM versus temperature is given in Figure 4b. The emission band position and FWHM versus temperature (T) are extracted, as shown in Figure 4c.…”

“…Thus, the luminescence in this compound comes from the STE in one CuBr x cluster. However, the organic ligand of TBA + can work as a confining agent and a cation component, play an important role in confining the STE, and lead to the emission process …”