Pure White Emission with 91.9% Photoluminescence Quantum Yield of [(C₃H₇)₄N]₂Cu₂I₄ out of Polaronic States and Ultra-High Color Rendering Index

Abstract

Recently, cuprous halide perovskite-type materials have drawn tremendous attention for their intriguing optical properties. Here, a zero-dimensional (0D) Cu­(I)-based compound of [(C3H7)4N]2Cu2I4 ([C3H7)4N]+ = tetrapropylammonium cation) was synthesized by a facile solution method, a monoclinic system of P21/n symmetry with a Cu2I4 2– cluster as the confined structure. The as-synthesized [(C3H7)4N]2Cu2I4 exhibits bright dual-band pure white emission with a photoluminescence quantum yield (PLQY) of 91.9% and CIE color coordinates of (0.33, 0.35). Notably, this compound also exhibits an ultrahigh color rendering index (CRI) of 92.2, which is comparable to the highest value of single-component metal halides reported recently. Its Raman spectra provide a clear spectral profile of strong electron–phonon interaction after [(C3H7)4N]+ incorporation, favoring the self-trapped exciton (STE) formation. [(C3H7)4N]2Cu2I4 can give dual-STE bands at the same time because of the Cu–Cu metal bond in a Cu2I4 2– cluster, whose populations could be scaled by temperature, together with the local dipole orientation modulation of neighboring STEs and phase transition related emission color coordinate change. Particularly, the outstanding chemical- and antiwater stability of this compound was also demonstrated. This work illustrates the potential of such cuprous halide perovskite-type materials in multifunctional applications, such as lighting in varied environments.

Highly Efficient Broadband Green Emission of (TPA)CuCl2 Single Crystals: Understanding the Formation of Self-Trapped States

“…In addition, the calculated band gap of (TPA)­CuCl 2 is 3.82 eV, slightly lower than the experimental value (Figure c). This difference between experiment and theory is often explained by the fact that the DFT calculation often underestimates the band gap of semiconductor materials . Interestingly, the VBM and CBM are governed by flat bands, which reveals that (TPA)­CuCl 2 possesses highly localized electronic states.…”

The templating effect of diammonium cations on the structural and optical properties of lead bromide perovskites: a guide to design broad light emitters

“…Indeed, (1,4-PDA)PbBr 4 shows a large DE and consistently shows a very promising intense luminescence. 29 We then consider the variation of the luminescence bandwidth, estimated by fitting the main emission component (at 650 nm and 550 nm) for (1,3-PDA)PbBr 4 and (1,4-PDA)PbBr 4 , respectively, and at 420 nm for (1,4-XDA)PbBr 4 with a Gaussian and taking its FWHM (Fig. 8b).…”

“…Indeed, (1,4-PDA)PbBr 4 shows a large Δ E and consistently shows a very promising intense luminescence. 29…”

Organic–Inorganic Hybrid Cuprous‐Based Metal Halides for Warm White Light‐Emitting Diodes

“…[ 14 , 15 , 16 , 17 , 18 , 19 , 20 ] In addition to these narrowband emissions, the broadband emission which is a prerequisite for yielding warm white light can be also achieved with these Cu + ‐based compositions, such as CsCu 2 I 3 , [KC 2 ] 2 [Cu 4 I 6 ] (C = 12‐crown‐4 ether), [(C 3 H 7 ) 4 N] 2 Cu 2 I 4 , (C 16 H 36 N)CuI 2 , (Gua) 3 Cu 2 I 5 (Gua = guanidine), etc. [ 21 , 22 , 23 , 24 , 25 ] However, despite the broadband emission, very few of these materials exhibit the desirable warm white light which features CCT value of around 2700 to 4000 K. Besides, one can see that most of these Cu + ‐based broadband emissive halides are iodide compounds, which severely restricts the possible adjustment of the spectral response through halide composition. The aforementioned facts highlight the urgency to develop new single‐component phosphors which have merits of broadband warm white‐light emission, low‐cost processing, nontoxicity, high PLQY (without extrinsic doping), and high color stability.…”