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Herein, a novel molecular SO2‐Bri‐DSB based on the sulfone‐bridged distyrylbenzene derivative is synthesized, and its organic crystal is fabricated. It has a very high photoluminescence (PL) quantum efficiency in the solution and crystalline state, i.e., dual‐state emission (DSE), and the corresponding PL mechanism is clarified in detail using the transient absorption and transient PL test. The PL behaviors in the monomolecular state and organic crystal are compared. In addition, the optical anisotropy of the SO2‐Bri‐DSB crystal is thoroughly investigated using various polarization‐dependent spectroscopy techniques. The time evolution of anisotropy is composed of a step behavior caused by the anisotropy of the electronic transition and a slow enhancing process with a lifetime of 4.86 ns, which is governed by the change in emission lifetime due to the anisotropy. The space‐resolved evolution of the optical anisotropy is investigated using the polarization‐dependent light wave‐guiding test and exhibits that the emission anisotropy gradually decreases with length, and it has a longer effective propagation length than the polarization emission signal. The findings provide insight into the intrinsic optical anisotropy of single‐molecular crystals and indicate that these materials have enormous potential in the domains of polarization lighting and display. [ABSTRACT FROM AUTHOR]

All‐inorganic perovskite quantum dots (QDs) with high photoluminescence quantum yield, narrow spectral bandwidth, and broad spectral tunability have broad applications. However, perovskite QDs suffer from poor stability and the fast anion‐exchange reaction between different halide ions. Herein, we embedded green‐light‐emitting CsPbBr3 QDs and red‐light‐emitting CsPb(Br/I)3 QDs into carboxyl‐containing polymethyl methacrylate (PMMA) by the hot‐injection method. As a result, the as‐prepared perovskite@PMMA composites not only retain high luminescence but also exhibit good water resistance. Moreover, this treatment prevents anion exchange between different halide QD particles in the solid state. The applications in light‐emitting diodes and cellular labeling agents are also carried out to demonstrate their good stability. Waterproof particles: CsPbBr3 particles were successfully encapsulated into carboxyl‐containing PMMA and exhibited good stability in water. The water resistance of 500 nm CsPbBr3@PMMA composites was tested (figure shows photographs of the composites water solution under daylight and UV light). The relative PL emission intensity decreased very slowly over time, retaining 90% of its original value after 12 h exposure to water. [ABSTRACT FROM AUTHOR]

Carbon dots (CDs) have attracted extensive attention over the past decade due to their excellent advantages. However, few attempts have been reported for realizing the long-wavelength emission, especially for obtaining efficient solid-state red emission with high photoluminescence quantum yield (QY). Herein, we developed highly red light emitting CDs by the step-by-step surface modifications of the nitrogen-doped CDs. By introducing hexadecyltrimethyl ammonium bromide to modulate a red CD aqueous solution, the photoluminescence QY increases from 23.2% to 43.6%. Furthermore, we dispersed CDs in a PVP matrix for a solid-state film, where the solid-state quenching was effectively suppressed, and high QY (41.3%) of red light emission was achieved. Taking advantage of the as-prepared red light emitting CDs combining with the reported high quantum yield blue and green light emitting CDs, we realized UV-pumped WLEDs with tunable correlated color temperature from 7879 to 2961 K. Moreover, a high color rendering index (CRI) of 93 for WLEDs was realized, which is superior than the best records for the semiconductor quantum dot based WLEDs. Finally, the red light emitting CDs were demonstrated to have promising application as a red color converter in traditional YAG-based WLEDs to improve their CCT and CRI. [ABSTRACT FROM AUTHOR]

The photoluminescence (PL) characteristics of semiconductor CdSe quantum dots (QDs) aggregated on Cu nanowires (NWs) were studied in detail. The PL relaxation dynamic data show that Cu NWs improve the PL intensity of CdSe QDs by accelerating the emission relaxation rate. The temperature-dependent PL data and excitation intensity-dependent PL data suggest that the activation energy of CdSe QDs might decrease due to the excellent heat transfer properties and the plasmon effect of Cu NWs. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The photoluminescence (PL) characteristics of MEH-PPV hybrid films blended with Au nanoparticles are studied in detail. Due to the strong coupling effect between the surface plasmon of Au nanoparticles and the emission of MEH-PPV, the introduction of Au nanoparticles could enhance the PL intensity and modulate the shape of absorption and excitation spectra, according to our steady spectroscopy experiments. Besides, the relaxation dynamic experiments show that the non-radiative rate in the hybrid system decreases. The temperature and the excitation intensity (EI)-dependent PL spectral data indicate that hybrid MEH-PPV films have lower activation energy and higher thermal exchange rate. As a result, the thermal accumulation effect and the non-linearity of EI-induced PL enhancement are suppressed in hybrid films. [ABSTRACT FROM AUTHOR]

The 3-(furan-2-yl)-2-(4-{[(2-hydroxy-5-methylphenyl)methylidene]amino}phenyl)prop-2-enenitrile (LAXYUI)), acting as a model, is a type of outstanding organic fluorophore. Using a transient absorption approach, the excitation relaxation behavior of LAXYUI in the monomolecular system and ordered crystals was identified. The polarization optical properties of LAXYUI crystals, including anisotropy of absorption and photoluminescence, polarization PL decay at different temperatures, and the evolution of optical anisotropy as a function of propagation length, are thoroughly investigated using a series of home-built polarization optical techniques. Our results can help people better understand the time- and space-dependent optical anisotropy that occurs in organic crystals, which will be important in the future to improve or broaden the performance of polarization optical systems based on organic crystals. • The aggregation molecule has a longer excited state lifetime and a stronger fluorescence. • The fluorescence lifetime of the crystal changes periodically with the polarization direction of the excitation. • Under horizontal excitation, the fluorescence lifetime is shortened more obviously with the increase of temperature. • The space-dependent evolution of anisotropy should be assigned to the difference of refractive index along the axis. [ABSTRACT FROM AUTHOR]

Although two-dimensional lead halide based perovskite has been developed for nearly five years, the room temperature preparation for achieving high efficiency Mn2+ emission in the lead halide perovskites is still facing huge challenges. Herein, we studied photoluminescent properties of highly emitting Mn2+ ions doped PEA 2 PbBr 4 perovskite platelets synthesized at room temperature by a facile hydrobromic acid-assisted (HBr-assisted) solid-liquid mixing strategy. The Mn-doped platelets with different Mn doping levels were synthesized by controlling Mn/Pb molar feed ratio and HBr addition volume. The photoluminescence (PL) quantum yield (QY) of orange-color (605 nm) of Mn-doped platelets reached 98%. Their optical properties were studied by steady-state and time-resolved PL spectroscopy. The temperature-dependent PL spectra revealed that the improvement mechanism of Mn luminescence and thermal stability was related to the reduction of the nonradiative defect/trap states through the HBr-induced surface passivation and enhancement of the exciton-to-Mn2+ energy transfer. This work provides a facile HBr solution-assisted method for preparing high-quality 2D Mn-doped perovskite platelets with stable and efficient luminescence. The two-dimensional Mn-doped PEA 2 PbBr 4 perovskite platelets with photoluminescence quantum yield of 98% and single-exponential Mn emission decay were prepared by a facile HBr-assisted strategy at room temperature. The improvement of luminescence is attributed to the reduction of the nonradiative defect/trap states and enhancement of the exciton-to-Mn2+ energy transfer. [Display omitted] • The 2D Mn-doped PEA 2 PbBr 4 perovskite platelets were synthesized by a facile HBr-assisted strategy at room temperature. • The Mn2+ PL QY up to 97% was achieved in orange-emitting Mn-doped PEA 2 PbBr 4 perovskite platelets. • The improved PL was attributed to the suppressed defect states and enhanced exciton-to-Mn energy transfer. [ABSTRACT FROM AUTHOR]

The carrier dynamics and the radiative channel together govern the performance of optoelectronic devices based on perovskite nanocrystals (NCs). In order to further understand their relationship, the pressure-dependent spectral test is employed, which scans the photo-physical properties of CsPbI 3 NCs. The carrier dynamics involving monomolecular and bimolecular recombination slow down with pressure, which decreases the photoluminescence quantum yield (PLQY). The former is affected by the variance of the shallow defect and both of them are sensitive to the phase transition at 0.39 GPa, which is confirmed by the pressure-dependent PL and absorption spectral data. The radiative lifetime, originated from a part of bimolecular recombination, prolongs with pressure, even though the PLQY decreases simultaneously. The photo-physical characteristics as mentioned is mainly originated from the lattice shrinkage induced by pressure. Our work provides clues for optimizing the performance of lighting and displaying devices based on inorganic perovskites NCs. • The photo-physical characteristics of CsPbI 3 NCs under high pressure is studied by many types of spectral tests. • The CsPbI 3 NCs undergo a phase transition at 0.39 GPa. • With pressure, the PL quantum yield (QY) of CsPbI 3 NCs decreased significantly. • Pressure affects the competition between radiative and non-radiative channels of CsPbI 3 NCs. [ABSTRACT FROM AUTHOR]