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Cesium lead halide (CsPbX3, X = Cl, Br, and I) perovskite nanocrystals (NCs) exhibit efficient anti‐Stokes photoluminescence (ASPL) upon sub‐gap single‐photon excitation, which has great potential for all‐solid‐state laser cooling. However, the mechanism responsible for the ASPL still remains elusive. Here, ASPL properties of CsPb(BrI)3 NCs and CsPbI3 NCs in inorganic solid matrix are investigated. Excitation wavelength‐ and power‐dependent ASPL demonstrates that it is a phonon‐assisted single‐photon process. Femtosecond transient absorption spectra show that ASPL is mediated by the Urbach tail states, where localized excitons are generated upon sub‐gap excitation. Through electron–phonon coupling, these localized excitons change into free exciton to generate the exciton bleaching, and then thermally dissociate into free carriers accompanied by band edge bleaching, leading to the efficient ASPL. Such a two‐step up‐conversion process is further confirmed by the carrier temperature extracted from the band edge bleaching band. This work deepens the understanding of ASPL in CsPbX3 NCs, and is valuable for the development of materials for solid‐state laser cooling. [ABSTRACT FROM AUTHOR]

The concept of doping Mn2+ ions into II–VI semiconductor nanocrystals (NCs) was recently extended to perovskite NCs. To date, most studies on Mn2+ doped NCs focus on enhancing the emission related to the Mn2+ dopant via an energy transfer mechanism. Herein, we found that the doping of Mn2+ ions into CsPbCl3 NCs not only results in a Mn2+‐related orange emission, but also strongly influences the excitonic properties of the host NCs. We observe for the first time that Mn2+ doping leads to the formation of Ruddlesden–Popper (R.P.) defects and thus induces quantum confinement within the host NCs. We find that a slight doping with Mn2+ ions improves the size distribution of the NCs, which results in a prominent excitonic peak. However, with increasing the Mn2+ concentration, the number of R.P. planes increases leading to smaller single‐crystal domains. The thus enhanced confinement and crystal inhomogeneity cause a gradual blue shift and broadening of the excitonic transition, respectively. [ABSTRACT FROM AUTHOR]

[Display omitted] • Luminous CsPbX 3 @SiO 2 nanofibers was synthesized. • CsPbX 3 @SNFs featured well-dispersed nanocrystals within the SNFs (PLQY > 60 %). • CsPbBr 3 @SNFs exhibited enhanced stabilities and excellent temperature-dependency. • CsPbBr 3 @SNFs presented a wide temperature-response range and reversibility. • CsPbX 3 @SiO 2 nanofibers demonstrated potential value for non-contact temperature probes. Non-contact thermometry has been proved a promising technique for temperature sensing and monitoring in biological systems, running turbine blades, operating bearings, mechanical or electrical devices. Herein, we developed a one-step electrospinning technique to fabricate rarely reported CsPbX 3 @SiO 2 nanofibers (CsPbX 3 @SNFs) via in-situ crystallization perovskite CsPbX 3 nanocrystals (NCs) inside silica nanofibers (SNFs) that provided excellent encapsulation of NCs by silica, and excellent temperature-dependence for non-contact temperature probes. The fabricated CsPbBr 3 @SNFs featured well-dispersed CsPbBr 3 nanocrystals (∼5–6 nm) within the SNFs (∼200–500 nm), higher photoluminescence quantum yields (>60 %), and readily tunable emission wavelengths by simple variation of halide compositions. Additionally, due to effective protection from silica, CsPbBr 3 @SNFs had improved stabilities towards heat, UV irradiation, and air, and preserved their remarkable optical performance. Moreover, the CsPbBr 3 @SNFs presented excellent temperature-dependency towards PL intensity, a wide temperature-response range (303–473 K), and temperature-dependent reversibility (>10 heating/cooling cycles), which confirmed its potential for application as a stable and sensitive non-contact temperature probe. This paper provides a novel strategy for fabricating robust luminous perovskites with environmental stability, while greatly broadening the photoelectric applications of perovskites, especially for non-contact temperature probes. [ABSTRACT FROM AUTHOR]

Lead halide perovskites (LHPs) are promising candidates for photovoltaic applications as they exhibit large carrier diffusion lengths and long carrier lifetimes among many other interesting properties. One of the widely accepted mechanisms for these properties is polaron formation, which is mainly driven by octahedral distortions of the inorganic framework. Since structure modifications of the framework largely affect associated distortions, we investigated Mn-doped and undoped CsPbX 3 (where X = Cl, Br, Cl/Br) using a local probe via micro-Raman spectroscopy and density functional theory (DFT) calculations for polaron formation. Our results highlight a new vibrational lattice mode at 132 cm -1 due to polaronic distortion upon photoinduction. From the DFT studies, we have shown that the polaronic states are dominated by the B-site cation in the perovskite structure, but it is the strong covalent overlap of the halide which determines its stability. This elucidation to map polaronic signatures with excellent spatial resolution using traditional Raman spectroscopy can be used as a simple tool to understand the structural changes and their impacted electronic properties and thus design superior devices using its in situ applications.

Inorganic cesium lead halide perovskites CsPbX 3 nanocrystals (NCs) have been widely used in optoelectronic applications due to their excellent optical properties. Furthermore, the final morphology and size of as-grown CsPbX 3 NCs play crucial roles in determining their stability and luminescent properties. Here, CsPbBr 3 NCs with various morphologies such as nanocubes, nanospheres, nanorods (NRs) and nanowires (NWs) have been fabricated by controlling the amount of solvent octadecene (ODE), the concentrations of trioctylphosphine oxide (TOPO)/tetradecylphosphonic acid (TDPA), the reaction temperatures and the final cooling rate. Finally, high-quality CsPbBr 3 NWs exhibiting cubic phase have been successfully obtained by optimizing the reaction parameters. These well-controlled CsPbBr 3 NWs with aspect ratio ~19 show great potential in helping nanodevice development. In summary, this study provides important insights for producing inorganic perovskite materials with tunable morphologies and properties for multi-applications. • CsPbBr 3 NCs with various shapes are fabricated via tuning reaction parameters. • High-quality CsPbBr 3 nanowires with aspect ratio ~19 are synthesized. • Synergistic mechanism of CsPbBr 3 NCs' morphology evolution is investigated. [ABSTRACT FROM AUTHOR]

All-inorganic lead halide perovskite nanocrystals (NCs) as new emerging semiconducting luminescent materials have attracted tremendous attention for designing optoelectronic devices. We have synthesized high quality of the CsPbX 3 NCs with tunable entire visible spectral region by a modified lower temperature method, featured with facile, low-cost and easily operating in an open environment without vacuumization or glovebox system. Besides, we have investigated the incorporation of Ni and K ions into CsPbX 3 NCs by adjusting all kinds of composition concentration from halogen salts, based on above mentioned preparation method. The absolute photoluminescence quantum yields (PLQYs) of doped CsPbX 3 NCs with different dopant (Ni or K ions) concentration were discussed. It is found that a certain amount of doping is beneficial for suppressing the defects and improving the lattice structure of nanocrystals, whereas an excessive dopant may induce quenching centers of the emission. In addition, a glorious absolute PLQYs of doped CsPbX 3 NCs can be obtained by our method, especially for CsPbBr 3 and CsPbI 3 NCs, and nearly reach 80%. • CsPbX3 NCs were synthesized operating in an open environment without vacuumization or glovebox system. • Ni and K ion doped into CsPbX 3 NCs for improving the PLQYs and stability. • A glorious absolute PLQYs of doped CsPbX3 NCs and high stability can be obtained. [ABSTRACT FROM AUTHOR]

To improve the stability and enable luminescent devices, colloidal perovskite nanocrystals (NCs) are usually encapsulated by polymer host matrices. Here, colloidal CsPbX 3 (X = Cl, Br or I, or mixture) NCs with bright emissions covering wide color gamut (~410–700 nm) are incorporated into the off-stoichiometry thiol-ene (OSTE) for solid state luminescence. The impact of polymer encapsulation on electronic transitions is investigated by comparison of absorption, photoluminescence (PL), and time resolved PL (TRPL) of the CsPbX 3 NCs before and after the encapsulation by the OSTE. The PL bandwidth increase pronouncedly, while the PL peak position apparently blue shifts after encapsulation. The spectral changes suggest the energy transfer between the CsPbX 3 NCs and OSTE matrix and decreased exciton binding energy due to the suppressed dielectric screen effect, which are further validated by the TRPL results. This work sheds light on the fluorescence of CsPbX 3 NCs incorporated in the polymer host matrices, which will facilitate their future applications in light-emitting and other optoelectronic devices. Image 1 • The colloidal CsPbX 3 NCs are incorporated into the off-stoichiometry thiol-ene (OSTE) for solid state luminescence. • The impact of polymer encapsulation on electronic transition is investigated by comparison of absorption, PL, time resolved PL (TRPL), and PLQYs. • The spectral changes suggest the energy transfer due to the suppressed dielectric screen effect. • The model of energy transfer is further validated by an additional lifetime parameter in the TRPL of the CsPbX 3 NCs-OSTE composites. [ABSTRACT FROM AUTHOR]

• CsPbX 3 /CN heterostructure were constructed to improve the stability of CsPbX 3. • CsPbBr 3 /CN is a type I, whereas CsPbCl 3 /CN a type II heterostructure. • CsPbX 3 /CN composite enhanced light-harvesting and improved charge recombination. • Both CsPbX 3 /CN composite exhibit the excellent photocatalytic activity. • CsPbX 3 /CN composite can degrade photocatalytically a type of penicillin. Fabrication of CsPbX 3 (X = Cl, Br)/graphitic carbon nitride (CN) composite has proved to be an efficient way to improve the stability of CsPbX 3 nanocrystals (NCs) and improve their photocatalytic activities. Here, the CsPbBr 3 /CN and CsPbCl 3 /CN heterostructures were successfully prepared, based on the band structure, the CsPbBr 3 /CN is indexed as a type I heterostructure, and CsPbCl 3 /CN is indexed as a type II heterostructure. Both CsPbX 3 /CN heterostructure could facilitate the electron-hole pairs (e−-h+) separation and exhibit the outstanding photocatalytic activity for penicillins 6-aminopenicillanic acid (6-APA) degradation under visible light, the degradation rates of 6-APA with CsPbCl 3 /CN and CsPbBr 3 /CN composite were about 78.11 and 83.31% in 120 min, respectively. The improved photocatalytic activity of the CsPbX 3 /CN heterostructures could be attributed to the favourable adsorbability, the enhanced light-harvesting ability, the efficient charge separation ability, as well as the synergistic effects of CsPbX 3 NCs and CN. This work may not only open up a new insight for design of CsPbX 3 -based heterostructure as novel photocatalyst but also provide a new possibility for photocatalytic applications of perovskites-based NCs. [ABSTRACT FROM AUTHOR]