Colloidal all‐inorganic perovskites nanocrystals (NCs) have emerged as a promising material for display and lighting due to their excellent optical properties. However, blue emissive NCs usually ...suffer from low photoluminescence quantum yields (PLQYs) and poor stability, rendering them the bottleneck for full‐color all‐perovskite optoelectronic applications. Herein, a facile approach is reported to enhance the emission efficiency and stability of blue emissive perovskite nano‐structures via surface passivation with potassium bromide. By adding potassium oleate and excess PbBr2 to the perovskite precursor solutions, potassium bromide‐passivated (KBr‐passivated) blue‐emitting (≈450 nm) CsPbBr3 nanoplatelets (NPLs) is successfully synthesized with a respectably high PLQY of 87%. In sharp contrast to most reported perovskite NPLs, no shifting in emission wavelength is observed in these passivated NPLs even after prolonged exposures to intense irradiations and elevated temperature, clearly revealing their excellent photo‐ and thermal‐stabilities. The enhancements are attributed to the formation of K‐Br bonding on the surface which suppresses ion migration and formation of Br‐vacancies, thus improving both the PL emission and stability of CsPbBr3 NPLs. Furthermore, all‐perovskite white light‐emitting diodes (WLEDs) are successfully constructed, suggesting that the proposed KBr‐passivated strategy can promote the development of the perovskite family for a wider range of optoelectronic applications.
High‐quality blue‐emitting CsPbBr3 nanoplatelets (NPLs) are synthesized via a facile potassium bromide‐enriched surface passivation. The resultant blue‐emitting (≈450 nm) CsPbBr3 NPLs show a high PLQY of 87% with excellent thermal stability and photostability. Furthermore, white light LEDs based on the mixture perovskite materials including the blue‐emitting NPLs are constructed, demonstrating a wide color gamut.
Organic semiconductor lasers (OSLs) have emerged as particularly challenging. One of the major issues preventing the successful realization of lasing from organic emitters under electrically pumped ...conditions is the inevitable population of triplet excitons. Herein, a novel concept is presented to construct triplet–singlet guest–host gain systems with incorporating iridium complexes as the triplet sensitizers and a fluorescent conjugated polymer as the gain media to achieve light amplification. The direct triplet–singlet energy transfer process is confirmed by photoluminescence excitation spectra, photoinduced absorption spectroscopy, and fluorescence transients of the blend samples. Successful light amplification with a threefold lower amplified spontaneous emission threshold and much better lasing performance is demonstrated for the resulting triplet–singlet guest–host system as compared with the corresponding gain system without triplet sensitizers. Moreover, under electrically driven conditions, the fluorescent organic light‐emitting diodes (OLEDs) based on the triplet–singlet guest–host systems with “triplet sensitizers” exhibit enhanced electrical performance relative to those without. The work suggests an effective general methodology to utilize both the singlet and triplet excitons to contribute to the light amplification with excellent electrical performance in OLEDs, opening prospects toward attempting electrically pumped OSLs.
An effective general methodology to utilize triplet excitons to contribute to light amplification with excellent electrical performance is presented. The triplet energy is managed by converting triplet excitons to singlet excitons via Förster energy transfer. This methodology is believed to be beneficial for addressing the challenges toward attempting electrically driven organic semiconductor laser diodes.
Developing semiconductors with broad gain bandwidth has always been at the forefront of laser technologies. The variation in feedback resonators can provide a useful tool for producing a relatively ...wide range of discrete lasing wavelengths. However, the lasing wavelength range is limited by the fundamental gain bandwidth of the semiconductor itself. Gain bandwidth engineering for full‐color range lasing though remains a daunting challenge. Considering the abundant energy levels of organic semiconductors, the authors stride over the barrier of the gain bandwidth limitation and demonstrate the dynamically tunable amplification/lasing across the entire emission range by leveraging on Förster resonance energy transfer (FRET)‐assisted guest–host blends. The unprecedented tunability in amplification and lasing is governed by energy transfer process, which enables them to achieve wavelength‐tunable semiconductor lasers spanning the full visible region of the electromagnetic spectrum. Their distributed feedback (DFB) lasers using these guest–host blends as gain media cover almost all CIE color gamut (94%), which is 170% more perceptible colors than standard Red Green Blue color space. These insights can guide the versatile and convenient design of organic semiconductor materials transcending the current gain bandwidth limitation, paving the way for next generation of optoelectronic devices.
A fundamental strategy to design organic semiconductors with tunable gain bandwidth is presented. By leveraging on Förster resonance energy transfer (FRET)‐assisted guest–host blends, the authors demonstrate the dynamically tunable amplification/lasing across the entire emission range. Their insights can guide the design of semiconductor materials transcending current gain bandwidth limitation, paving the way for next generation of optoelectronic devices.
In the present study, quantum dot (QD) capped magnetite nanorings (NRs) with a high luminescence and magnetic vortex core have been successfully developed as a new class of magnetic-fluorescent ...nanoprobe. Through electrostatic interaction, cationic polyethylenimine (PEI) capped QD have been firmly graft into negatively charged magnetite NRs modified with citric acid on the surface. The obtained biocompatible multicolor QD capped magnetite NRs exhibit a much stronger magnetic resonance (MR) T2* effect where the r2* relaxivity and r2*/r1 ratio are 4 times and 110 times respectively larger than those of a commercial superparamagnetic iron oxide. The multiphoton fluorescence imaging and cell uptake of QD capped magnetite NRs are also demonstrated using MGH bladder cancer cells. In particular, these QD capped magnetite NRs can escape from endosomes and be released into the cytoplasm. The obtained results from these exploratory experiments suggest that the cell-penetrating QD capped magnetite NRs could be an excellent dual-modality nanoprobe for intracellular imaging and therapeutic applications. This work has shown great potential of the magnetic vortex core based multifunctional nanoparticle as a high performance nanoprobe for biomedical applications.
Rational molecular design allows for manipulating the chain conformations of polymer semiconductors by cooperative arrangement of bulky groups with steric hindrance effect and supramolecular groups ...with noncovalent attractions. Herein, a model polyfluorene with β-phase, poly4-(octyloxy)-9,9-diphenylfluoren-2,7-diyl-co-5-(octyloxy)-9,9-diphenylfluoren-2,7-diyl (PODPF), has been synthesized successfully via key Baeyer–Villiger rearrangement reaction. Its thin film exhibited excellent spectral stability without green band emission after thermal annealing at 200 °C under air and nitrogen ambients. The β-phases of PODPF in the concentrated toluene solution, organogels, and films have been characterized and confirmed by UV absorption and PL spectra as well as grazing-incidence X-ray scattering. The results suggest that the octyloxy substituents enable backbone planarization via van der Waals forces of the in-plane alkyl chains to overcome intrachain repulsion between fluorene monomers. Organic lasers using β-phase PODPF exhibit lower threshold than those of poly(9,9-dioctylfluorene), suggesting promising optical gain media. This observation suggested that supramolecular steric hindrance (SSH) is a promising molecular design of polymer semiconductors, and supramolecular steric polymers are one kind of model to get insight into the structure–function relationships for electrically pumped organic lasers in organic electronic and photonics.
Solution processed organic-inorganic hybrid perovskites are emerging as a new generation materials for optoelectronics. However, the electroluminescence is highly limited in light emitting diodes ...(LED) due to the low exciton binding energy and the great challenge in stability. Here, we demonstrate a super air stable quasi-two dimensional perovskite film employing hydrophobic fluorine-containing organics as barrier layers, which can store in ambient for more than 4 months with no change. The dramatically reduced grain size of the perovskite crystal in contrast to three dimensional (3D) perovskites was achieved. Together with the natural quantum well of quasi-two dimensional perovskite confining the excitons to recombination, the LED exhibited the maximum luminance of 1.2 × 10
cd/m
and current efficiency up to 0.3 cd/A, which is twenty fold enhancement than that of LED based on 3D analogues under the same condition.
Abstract
Colloidal all‐inorganic perovskites nanocrystals (NCs) have emerged as a promising material for display and lighting due to their excellent optical properties. However, blue emissive NCs ...usually suffer from low photoluminescence quantum yields (PLQYs) and poor stability, rendering them the bottleneck for full‐color all‐perovskite optoelectronic applications. Herein, a facile approach is reported to enhance the emission efficiency and stability of blue emissive perovskite nano‐structures via surface passivation with potassium bromide. By adding potassium oleate and excess PbBr
2
to the perovskite precursor solutions, potassium bromide‐passivated (KBr‐passivated) blue‐emitting (≈450 nm) CsPbBr
3
nanoplatelets (NPLs) is successfully synthesized with a respectably high PLQY of 87%. In sharp contrast to most reported perovskite NPLs, no shifting in emission wavelength is observed in these passivated NPLs even after prolonged exposures to intense irradiations and elevated temperature, clearly revealing their excellent photo‐ and thermal‐stabilities. The enhancements are attributed to the formation of K‐Br bonding on the surface which suppresses ion migration and formation of Br‐vacancies, thus improving both the PL emission and stability of CsPbBr
3
NPLs. Furthermore, all‐perovskite white light‐emitting diodes (WLEDs) are successfully constructed, suggesting that the proposed KBr‐passivated strategy can promote the development of the perovskite family for a wider range of optoelectronic applications.
To examine the single nucleotide polymorphism (SNP) distributed in exon 20, 21 and intron 20 of epidermal growth factor precursor gene (preproEGF) of Buyi and Han individuals.
Eleven primer sets were ...designed and synthesized for PCR, that genomic DNA of Buyi or Han individual was used as the template, to amplify and sequence respectively the large fragment DNA from preproEGF gene. BLAST programs were applied to compare and identify the SNPs from the sequenced PCR products or amplified DNA fragments.
4.5 kb DNA fragments long over 20th, 21st exon and 20th intron structures of preproEGF gene were got by PCR respectively from genomic DNAs of Buyi and Han individuals. Results of DNA sequencing showed two SNPs in 4. 5 kb fragment of Han individual, of which one was sited at C86380T of preproEGF gene and another positioned at 84580 bp (T/-), while one SNP was observed in Buyi individual, which was located at T84329C of preproEGF gene. GenBank dbSNP database showed that C86380T SNP in 20th intron of preproEGF gene h
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