Real-Time Observation of Anion-Exchange Reaction in Cs₃Cu₂Cl₅ Single Crystal

Abstract

Cs3Cu2Cl5 has attracted great attention in many photonic applications owing to its high photoluminescence quantum yield (PL QY), nontoxicity, and large Stokes shift. However, its labile nature to air and single-color emission have limited its practical use in display-related applications. In this work, a single crystal of Cs3Cu2Cl5 was grown with a user-friendly Cu2+ precursor. To tune the emission color and stability, the anion-exchange reaction was employed with trace amounts of I ions. The anion-exchanged crystals not only enabled a fine color tuning from sky-blue to emerald-green but also dramatically improved the chemical stability of Cs3Cu2Cl5. Microscopic imaging of an individual crystal flake demonstrated a uniform emission of cross section, which was quite different from conventional core/shell structures. Importantly, the anion-exchanged crystals retained a high PL QY up to 98%. Our work brings insights into the manipulation of self-trapped excitons, opening many avenues for stable photoelectric devices.

Ultrabright Light Emission Properties of All-Inorganic and Hybrid Organic–Inorganic Copper(I) Halides

“…The original structural reports in the Pearson’s database suggest that the Cs 3 Cu 2 I 5 -type Cs 3 Cu 2 Cl 5 (0D) can be obtained by a solid-state reaction of binary halides at 270 °C for 5 days, whereas the 1D polymorph (own type) is obtained by slow cooling a water solution containing binary reactants from 70 °C to room temperature. ,, We must stress here that there is a considerable amount of confusion regarding syntheses and structural and optical properties of these two polymorphs of Cs 3 Cu 2 Cl 5 , requiring further work for clarification. Thus, several recent studies on Cs 3 Cu 2 Cl 5 focusing on its bright green light emission proceeded with an assumption that the compound will form in the Pnma space group isostructural to the other members of the Cs 3 Cu 2 X 5 family. − However, the starkly contrasting green emission from Cs 3 Cu 2 Cl 5 as compared to the intense blue emission from Cs 3 Cu 2 Br 5 and Cs 3 Cu 2 I 5 within the same structure type has not been explained satisfactorily (notice that the chloride is said to give a lower energy emission as compared to higher energy emission from the bromide and iodide). An alternative scenario that the green emitting Cs 3 Cu 2 Cl 5 is the 1D polymorph crystallizing in the Cmcm space group with its own structure type has not been considered carefully, although there are recent reports supporting this claim. ,, We note that the recent publications on Cs 3 Cu 2 Cl 5 so far are contradictory in this regard as a number of studies inaccurately describe the Cmcm structure as made of dimers and, conversely, the Pnma structure as made of 1D chains. , Altogether, a confusing picture emerges for Cs 3 Cu 2 Cl 5 in which structure types are assigned seemingly arbitrarily, and the subsequent structure description within the same publication does not agree with the assigned structure.…”

Transparent and Planar Cs3Cu2Cl5 Crystals for Micrometer-Resolution X-ray Imaging Screen

“…The transmission spectrum revealed a high transparency up to 86% in the whole visible range (Figure b). The time-resolved PL curve at room temperature was well fitted by a single exponential function ( R 2 = 0.9997) featuring a lifetime of 112 μs (Figure c), which echoed well with many previous reports. , Due to the large Stokes shift and negligible reabsorption effect, the photoluminescence quantum yield (PL QY) approached unity (∼100%), which was consistent with previous literatures (Figure S5). , …”

“…The time-resolved PL curve at room temperature was well fitted by a single exponential function (R 2 = 0.9997) featuring a lifetime of 112 μs (Figure 2c), which echoed well with many previous reports. 30,31 Due to the large Stokes shift and negligible reabsorption effect, the photoluminescence quantum yield (PL QY) approached unity (∼100%), which was consistent with previous literatures (Figure S5). 25,28 The high-quality crystal flake enabled an accurate measurement of the absorbance and PL intensity.…”

Yellow Emissive CsCu2I3 Nanocrystals Induced by Mn2+ for High-Resolution X-ray Imaging

“…Recently, low-dimensional Cu­(I)-based perovskite or derivatives have attracted extensive attention as scintillators due to their high PL quantum yield (PLQY), easy fabrication, good stability and nontoxicity. − For example, Tang’s group synthesized one-dimensional (1D) perovskite Rb 2 CuCl 3 with ultrahigh PLQY (99.4%) and good stability via a facile solution method. The Rb 2 CuCl 3 also demonstrates an acceptable LY of 16600 photons MeV –1 under X-ray irradiation .…”