Photoluminescence and Raman Spectra of One-Dimensional Lead-free Perovskite CsCu₂I₃ Single-Crystal Wires

Abstract

Lead-free highly luminescent CsCu2I3 perovskite has attracted much attention recently, but agreements on basic optical properties have remained unsettled. By correlating X-ray diffraction with the photoluminescence (PL) of CsCu2I3 single-crystal wires, we first show that blue PL at 420 nm originates from CuI. We then exclude defect states as a source for the broadband emission centered at 570 nm from the lack of defect absorption, PL under sub-bandgap photoexcitation, observations of a linear dependence of PL intensity on excitation laser power, and a strong spectral blueshift under mild hydrostatic pressure. Finally, using a model of the self-trapped exciton and the associated coordinate configuration diagram, we explain pressure evolutions of PL energy, intensity, and lifetime. Single-crystal wires also enable us to obtain polarization-dependent Raman spectra down to 10 cm–1 and confirm their respective ambient crystal structure of orthorhombic Cmcm and phase transition to Pbnm at ∼5 GPa.

Large scale synthesis of carbon dots for efficient luminescent solar concentrators

“…Large Stokes shift in semiconductors might be due to the self-trapped exciton or the electron delocalization. 48,49 In our case, the metal cation capped C-dots might have a stable intermedium surface energy state, contributing to a large Stokes shift. 32 Depending on the type of cation, the traps could be formed during the synthesis process, which serve as a recombination center (Fig.…”

“…Typically, the optical properties of the C-dots strongly depend on their core size/composition and their surface functional groups. 42 Compared to inorganic semiconductors, 48,49 the C-dots exhibited molecular-like behaviors. Thus, we still use the LUMO and HOMO for their energy structures as shown in Fig.…”

Anisotropic Growth of Centimeter‐Size CsCu2I3 Single Crystals with Ultra‐Low Trap Density for Aspect‐Ratio‐Dependent Photodetectors

“…The strongly polarized Raman spectra indicate the high crystallinity of the CsCu 2 I 3 single crystal, especially the ultra‐long single crystal with a diameter of 200 µm. [ 33 ] The photoluminescence excitation (PL) spectrum in Figure 4c shows that CsCu2I3 single crystals with different aspect ratios displayed good optical feature and it sent out yellow emission at ≈580 nm, and 200 µm diameter single crystal displayed the strongest emission. In order to gain further insight into the carrier behavior, transient‐state PL characterization was performed on CsCu 2 I 3 single crystals with different aspect ratios.…”

Multimodal Luminescent Low-Dimension Cs2ZrCl6:xSb3+ Crystals for White Light-Emitting Diodes and Information Encryption

“…Recently, low-dimension vacancy-ordered double perovskites (A 2 BX 6 , A = Cs, K, Rb, B = Ti 4+ , Sn 4+ , Zr 4+ , Hf 4+ , Te 4+ , Pd 4+ , X = Cl, Br) have been regarded as high-potential WLED phosphors owing to their great chemical stability, broad-band emission, high PLQY, low cost, environmentally friendly nature, and so forth. − Moreover, the A 2 BX 6 perovskite has a typically low dimensionality, resulting in self-trapping excitons (STEs) because of strong exciton–phonon interactions, leading to broadband emission and large Stokes shift. − However, the emission of pure-phase A 2 BX 6 perovskites is low. ,,, Currently, metal ion doping has been considered as an effective method to improve the optical properties of perovskites. In this regard, rare-earth ions (Ce 3+ ), transition-metal ions (Pt 4+ ), and even some main-group metal ions (Bi 3+ , Sb 3+ , and Te 4+ ) have been successfully doped in A 2 BX 6 perovskites, which produces additional luminescence energy levels. ,− ,, Among them, Sb 3+ is a potential optically luminescent ion with red broad-band emission due to its special STE and low toxicity.…”