Coupling Intracompound Charge Transfer and Cluster‐Centered Excited States in Cu(I) Halide Hybrids for  Efficient White Light Emission

Abstract

0D hybrid organic–inorganic metal halides have attracted significant interest due to their unique optoelectronic properties, but attainment of efficient and stable white light emission (WLE) in such compounds remains a challenge. Here, efficient WLE via a molecular design that couples intracompound charge transfer and cluster‐centered excited states in 0D halide hybrids is demonstrated. Two Cu(I) halide hybrids, K(18‐crown‐6)Cu2Br3 and Na4(18‐crown‐6)5In2Cu4Br14·8H2O, are synthesized wherein luminescent [Cu4Br6]2− clusters are isolated from each other and surrounded by 18‐crown‐6 coordinated alkali metal cations. In the case of K(18‐crown‐6)Cu2Br3, [Cu4Br6]2− clusters are only partially isolated, leading to strong orange emission with a photoluminescence quantum yield (PLQY) of 53% under UV excitation. Strikingly, to a larger extent of isolation as that, in Na4(18‐crown‐6)5In2Cu4Br14·8H2O as a result of the incorporation of nonemissive [InBr4]− clusters, intense white light emission with a PLQY of 97% is achieved. The dual cluster‐centered states, coupled with a mixed metal‐to‐ligand and halide‐to‐ligand charge transfer state, are responsible for this bright white luminescence. This work provides new design principles for expanding the materials library for single‐component, solid‐state WLE.

Photophysical studies for Cu(i)-based halides: broad excitation bands and highly efficient single-component warm white-light-emitting diodes

“…In other words, the multiple excited states in DPCu 4 I 6 are easily coupled at RT to result in the bright yellow emission, and a similar behavior is also observed in (1,3-dppH 2 ) 2 Cu 4 I 8 $H 2 O 57 and Na 4 (18-crown-6) 5 In 2 Cu 4 Br 14 $8H 2 O. 58 Moreover, the excitation wavelength-dependent PL spectra at 80 K clearly reveal the attractive dual-band emission of DPCu 4 I 6 (Fig. 3c).…”

“…A prominent feature of this band is the stable peak position over a wide range of temperatures. 38,58 Fig. 3f shows the variation of the double emission band of DPCu 4 I 6 with temperature, and the spectral features allow us to attribute the observed emission at 707 nm to the 3 CC excited state and the one at 600 nm to the X/MLCT state.…”

Multi‐Stimuli Responsive Luminescence and Domino Phase Transition of Hybrid Copper Halides with Nonlinear Optical Switching Behavior

“…α-Gua 3 Cu 2 I 5 is composed of face-connected [CuI 4 ] 3À tetrahedra to form isolated [Cu 2 I 5 ] 3À unit separated by Gua + ions, which is different from the 0D structures of Cs 3 Cu 2 I 5 [20] and MA 3 Cu 2 Br 5 [21] composed of [CuX 4 ] 3À tetrahedron and [CuX 3 ] 2À triangle that are edge-sharing to form isolated [Cu 2 X 5 ] 3À unit. The range bond length of CuÀ I is 2.525(2)-2.850(2) Å, and the distance of adjacent Cu is 2.49 Å, which is lower than two times of van der Waals (vdW) radius of Cu (2.80 Å), [22] implying strong Cu•••Cu bonding interactions in this compound. [23] β-Gua 3 Cu 2 I 5 crystallizes in the CS monoclinic space group of C2/c (Figure 1b, c), and its asymmetric structural unit contains 1 Cu, 2.5 I atoms and 1.5 Gua + cations (Figure S2b).…”

Rational Design of a Super-Alkali Compound with Reversible Photoluminescence

“…In recent years, low-dimensional metal halides (LDMHs) have been extensively studied as promising PL materials thanks to their high exciton binding energies , and structural confinement effect. − Remarkably, some of these materials even show reversible and naked-eye perceivable PL color changes upon external stimuli. − Such disparate PL performance is understandable given that the structural rigidity can be increased for the resulting crystal by supramolecular interaction (PL enhancing mechanism) , or the dissipation of excited-state energy can be realized through rotation and vibration of the incorporated guest molecules (PL quenching mechanism) . Either way, the underlying principle of host–guest chemistry is at the core of the above findings.…”