Luminescence and thermal behaviors of free and trapped excitons in cesium lead halide perovskite nanosheets

Lao, Xiangzhou; Yang, Zhi; Su, Zhicheng; Wang, Zilan; Ye, Honggang; Wang, Minqiang; Yao, Xi; Xu, Shijie

doi:10.1039/c8nr01109e

Cited by 156 publications

(140 citation statements)

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“…By fitting the temperature dependent FWHM curve, the S factor was derived as 37.17 and the ℏ ω photon was 17.95 meV. The Huang–Rhys factor of Rb 2 CuBr 3 is much higher than that of most traditional luminescent materials, such as ZnSe, CdSe, and CsPbBr 3 , demonstrating its soft crystal nature and the easy formation of STEs in Rb 2 CuBr 3 . The specific excitation and recombination processes for Rb 2 CuBr 3 are shown in the schematic diagram of Figure f.…”

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confidence: 96%

Lead‐Free Halide Rb₂CuBr₃ as Sensitive X‐Ray Scintillator

et al. 2019

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into visible light that are further captured and converted into electrical signals by a following photomultiplier. [7][8][9][10][11] Scintillators have been actively utilized for radiation detection applications in many fields, like nondestructive inspection, medical imaging, and space exploration. Scintillator-based X-ray detectors are advantageous in terms of cost and stability than direct X-ray detectors (a-Se), and the current market of X-ray detectors is dominated by scintillators.The light yield of scintillators, as one of the most important figures of merit, determines the X-ray conversion efficiency and detection contrast. Liu and co-workers reported the good X-ray imaging properties from CsPbBr 3 nanocrystals [8] and Zhang et al. evaluated the light yield for CsPbBr 3 nanocrystals as 21 000 photons per MeV. [11] Such value is still much lower than traditional scintillators like Lu 1.8 Y 0.2 SiO 5 -Ce (LYSO, 33 200 photons per MeV), [12] CsI-Tl (54 000 photons per MeV) [12] and Gd 2 O 2 S-Tb (GOS, 60 000 photons per MeV) [13] etc. The major reason is that the small Stokes shift and the self-absorption effect for lead halide perovskites would severely restrict the light outcoupling efficiency in films and crystals, which require large thickness for complete X-ray attenuations. For scintillators, large Stokes shift and high photoluminescence efficiency are required to obtain high scintillation light yield. The recently emerged self-trapped exciton emissions from low dimensional perovskites exhibit large stokes shift and high PLQY, and may provide efficient X-ray scintillations, but have scarcely been studied. [14][15][16] Another severe issue restricting the applications of lead halide perovskite scintillators is the toxicity of lead element. The ionic nature of halide perovskites and high solubility in water may seriously harm the human health as well as the environment. It is thus of great significance to find lead-free perovskites or halide scintillators.Here we present 1D structured Rb 2 CuBr 3 as one new member of scintillators with exceptionally high light yield. Rb 2 CuBr 3 is obtained by direct reaction between RbBr and CuBr with phase-purity, high quality, and good stability. Its 1D crystal structure and soft crystal lattice facilitate the formation of self-trapped exciton, which emits at 385 nm with a large Stokes shift of 85 nm (0.91 eV) and 98.6% photoluminescence quantum yield. The high emission efficiency, large Stokes shift, strong X-ray attenuation, and good spectrum matching with the photomultiplier tube (PMT) or silicon photomultiplier Scintillators are widely utilized for radiation detections in many fields, such as nondestructive inspection, medical imaging, and space exploration. Lead halide perovskite scintillators have recently received extensive research attention owing to their tunable emission wavelength, low detection limit, and ease of fabrication. However, the low light yields toward X-ray irradiation and the lead toxicity of these perovskites severely restricts their practical ...

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confidence: 96%

Lead‐Free Halide Rb₂CuBr₃ as Sensitive X‐Ray Scintillator

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“…Namely, the lasing region moves faster than the PL with increasing strain. At room temperature, the 527 nm PL peak can be attributed to the emissions of free excitons with high energy, and the emission wavelength is dominated by bandgap rather than defects related energy levels. Therefore, the underlying mechanisms leading to the shifts of the lasing mode and PL emission are different in nature.…”

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confidence: 99%

Controllable Growth of Aligned Monocrystalline CsPbBr₃ Microwire Arrays for Piezoelectric‐Induced Dynamic Modulation of Single‐Mode Lasing

Yang

Zhuge

et al. 2019

Advanced Materials

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Since the appearance of semiconductor solid-state lasers in the 1960s, [1] lasers have shown tremendous potential in various applications, such as data communication, medical treatment, environmental science, and military defense. Up to now, enormous research efforts have been conducted to develop high-quality semiconductor lasers. [2] Multiple-mode lasers suffer from false signaling, random fluctuation, and instability which hinder their practical applications. [3,4] Therefore, efforts to achieve single-mode lasers have drawn much attention due to the monochromaticity, high stability, controllable output wavelength, and great potential of these lasers in practical applications, such as in on-chip optical communication. [5] Thus far, most single-mode lasers have been realized in the following four ways: 1) decreasing the cavity size to enlarge the free spectral range (FSR); [6,7] 2) fabricating distributed Bragg reflector (DBR) mirror structures or distributed feedback (DFB) CsPbBr 3 shows great potential in laser applications due to its superior optoelectronic characteristics. The growth of CsPbBr 3 wire arrays with well-controlled sizes and locations is beneficial for cost-effective and largely scalable integration into on-chip devices. Besides, dynamic modulation of perovskite lasers is vital for practical applications. Here, monocrystalline CsPbBr 3 microwire (MW) arrays with tunable widths, lengths, and locations are successfully synthesized. These MWs could serve as high-quality whispering-gallery-mode lasers with high quality factors (>1500), low thresholds (<3 µJ cm −2 ), and long stability (>2 h). An increase of the width results in an increase of the laser quality and the resonant mode number. The dynamic modulation of lasing modes is achieved by a piezoelectric polarization-induced refractive index change. Single-mode lasing can be obtained by applying strain to CsPbBr 3 MWs with widths between 2.3 and 3.5 µm, and the mode positions can be modulated dynamically up to ≈9 nm by changing the applied strain. Piezoelectric-induced dynamic modulation of single-mode lasing is convenient and repeatable. This method opens new horizons in understanding and utilizing the piezoelectric properties of lead halide perovskites in lasing applications and shows potential in other applications, such as on-chip strain sensing.

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“…At higher ranges for lasing (usually n~10 18 cm -3 for 3D perovskites [18]), the key factor that limits the carrier density under CW excitation originates from the Auger recombination coefficient c. It is also clear that the carrier density within perovskite films is proportional to P at low CW excitation intensities (usually lower than~1 to~1000 mW/cm 2 ). In this region, the radiative recombination type can be identified through the logarithmic slope of the CW power-dependent PL intensity ( Figure 3C), whereas slopes of 1 and 2 refer to excitonic (monomolecular) and free electron-hole (bimolecular) recombination, respectively [37,[53][54][55][56]. However, when P increases, the second-order term (bn 2 ) becomes comparable with the first-order term (an), resulting in the nonlinear relationship between P and n ( Figure 3B).…”

Section: Trends In Chemistrymentioning

confidence: 99%