Lead-based perovskites have received great attention due to their excellent optoelectronic
characteristics, but the instability and intrinsic toxicity of lead are still critical issues for their
practical applications. To overcome these drawbacks, exploring the nontoxic substitution of lead
in perovskites while maintaining the outstanding behaviors of perovskites is significantly
important. Recently, copper has been regarded as a promising candidate to replace lead due to its
low environmental effect, abundance, and low cost. Copper-based halides tend to form highquality
low-dimensional compounds with structural and compositional flexibility, and they have
been used for fabricating optoelectronic devices, such as light-emitting diodes (LEDs),
photodetectors, and X-ray scintillators.
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Lead-based perovskites have received great attention due to their excellent optoelectronic
characteristics, but the instability and intrinsic toxicity of lead are still critical issues for their
practical applications. To overcome these drawbacks, exploring the nontoxic substitution of lead
in perovskites while maintaining the outstanding behaviors of perovskites is significantly
important. Recently, copper has been regarded as a promising candidate to replace lead due to its
low environmental effect, abundance, and low cost. Copper-based halides tend to form highquality
low-dimensional compounds with structural and compositional flexibility, and they have
been used for fabricating optoelectronic devices, such as light-emitting diodes (LEDs),
photodetectors, and X-ray scintillators.
We synthesized all-inorganic ternary copper halides including spherical Cs
3Cu
2X
5 (X = Cl, Cl/Br,
Br, Br/I, and I) nanocrystals with PL peaks ranging from 440 to 530 nm, CsCu
2I
3 nanocrystals
with an emission peak of 575 nm, and deep-blue emissive A
2CuX
3 (A = K, Rb; X = Cl, Br)
nano/microcrystals with controllable morphologies. Among them, green luminescent Cs
3Cu
2Cl
5
and deep-blue luminescent K
2CuCl
3 possess a remarkable high photoluminescence quantum
yield (PLQY) value of ~100%. Moreover, with the incorporation of organic molecules into
ternary copper halides, their structures can be further tuned to obtain more emission colors in the
visible spectrum. Red-emissive A
6(DMSO)
12[Cu
8Br
13][Cu
4Br
4(OH)(H2O)] (ACB-DMSO, A = K,
Rb; DMSO = dimethyl sulfoxide, C
2H
6OS) and A
6(C
4H
8OS)
12[Cu
8X
13][Cu
4X
4(OH)(H
2O)] (ACX-THTO, A = K, Rb, and Cs; X = Cl, Br) with deep-red to to near-infrared emissions were
obtained. It was observed that the removal and addition of the solvent molecules resulted in the
reversible transformation between the hybrid copper halides with 0D copper clusters and allinorganic
copper compounds featuring one-dimensional (1D) chains. Furthermore, we conducted
the liquid-liquid diffusion method to synthesize diverse categories of alkali copper(I) iodide
(ACuI)-based (A = Na, K, Rb, and Cs) hybrid compounds with diverse structures. Their emission
peaks are in the range of 530-660 nm, which can be tuned by the composition of alkali metals
and organic molecules. The highest emission efficiency of 91% was achieved for
KCuI
2(C
4H
8OS)
2 (658 nm), and yellow emissive Rb
2Cu
2I
4(C
4H
8OS)
3 showed excellent stability
in the air. This solvent engineering is not only suitable for copper-based compounds, but it also
works for sodium antimony bromides. Yellow emissive Na
3SbBr
6(C
2H
6OS)
6 and orange emissive
Na
3SbBr
6(C
4H
8OS))
6 single crystals featuring 1D chains also can transform into each other.
Additionally, we demonstrated their utilization as ink for inkjet printing or emitters for downconversion
mono-color or white LEDs with excellent performance.
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