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Xiancheng Nie

Bio: Xiancheng Nie is an academic researcher from University of Science and Technology of China. The author has contributed to research in topics: Phosphorescence & OLED. The author has an hindex of 5, co-authored 7 publications receiving 92 citations.

Papers
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Journal ArticleDOI
TL;DR: Taking advantage of the AIE feature, the AIP molecules are fabricated into OLEDs as a homogeneous light-emitting layer, which allows for relatively small efficiency roll-off and shows an external electroluminescence quantum yield of up to 5.8%, more than the theoretical limit for purely fluorescent OLED devices.
Abstract: Aggregation-induced emission (AIE) is a beneficial strategy for generating highly effective solid-state molecular luminescence without suffering losses in quantum yield. However, the majority of reported AIE-active molecules exhibit only strong fluorescence, which is not ideal for electrical excitation in organic light-emitting diodes (OLEDs). By introducing various substituent groups onto the biscarbazole compound, a series of molecular materials with aggregation-induced phosphorescence (AIP) is designed, which exhibits two distinctly different phosphorescence bands and an absolute solid-state room-temperature phosphorescence quantum yield up to 64%. Taking advantage of the AIE feature, the AIP molecules are fabricated into OLEDs as a homogeneous light-emitting layer, which allows for relatively small efficiency roll-off and shows an external electroluminescence quantum yield of up to 5.8%, more than the theoretical limit for purely fluorescent OLED devices. The design showcases a promising strategy for the production of cost-effective and highly efficient OLED technology.

134 citations

Journal ArticleDOI
TL;DR: In this article, a series of fluorescent naphthalimides, which did not originally show observable phosphorescence in solution, as aggregates, in polymer films, or in any other tested host material, including heavy-atom matrices at cryogenic temperatures, can now efficiently produce ultralong RTP (ϕ=0.17, τ=243 ms) in phthalimide hosts.
Abstract: Manipulation of long-lived triplet excitons in organic molecules is key to applications including next-generation optoelectronics, background-free bioimaging, information encryption, and photodynamic therapy. However, for organic room-temperature phosphorescence (RTP), which stems from triplet excitons, it is still difficult to simultaneously achieve efficiency and lifetime enhancement on account of weak spin-orbit coupling and rapid nonradiative transitions, especially in the red and near-infrared region. Herein, we report that a series of fluorescent naphthalimides-which did not originally show observable phosphorescence in solution, as aggregates, in polymer films, or in any other tested host material, including heavy-atom matrices at cryogenic temperatures-can now efficiently produce ultralong RTP (ϕ=0.17, τ=243 ms) in phthalimide hosts. Notably, red RTP (λRTP =628 nm) is realized at a molar ratio of less than 10 parts per billion, demonstrating an unprecedentedly low guest-to-host ratio where efficient RTP can take place in molecular solids.

86 citations

Journal ArticleDOI
TL;DR: The reported molecular construct serves as an intermediary case between a fully conjugated donor-acceptor system and a donor/acceptor binary mix, which may provide important clues on the design and control of high-freedom molecular systems with complex excited-state dynamics.
Abstract: Aggregation-induced emission (AIE) has proven to be a viable strategy to achieve highly efficient room temperature phosphorescence (RTP) in bulk by restricting molecular motions. Here, we show that by utilizing triphenylamine (TPA) as an electronic donor that connects to an acceptor via an sp3 linker, six TPA-based AIE-active RTP luminophores were obtained. Distinct dual phosphorescence bands emitting from largely localized donor and acceptor triplet emitting states could be recorded at lowered temperatures; at room temperature, only a merged RTP band is present. Theoretical investigations reveal that the two temperature-dependent phosphorescence bands both originate from local/global minima from the lowest triplet excited state (T1). The reported molecular construct serves as an intermediary case between a fully conjugated donor-acceptor system and a donor/acceptor binary mix, which may provide important clues on the design and control of high-freedom molecular systems with complex excited-state dynamics. Aggregation-induced emission (AIE) has proven to be a viable strategy to achieve highly efficient room temperature phosphorescence (RTP) in bulk by restricting molecular motions. Here, the authors present an RTP design strategy by combining the concept of AIE and donor-acceptor motif and demonstrate unusual thermochromic dual phosphorescence.

65 citations

Journal ArticleDOI
TL;DR: In this paper, a series of naphthalene diimides with various electron-donor substituents on the nitrogen atoms were used to achieve red room temperature phosphorescence (RTP).

21 citations

Journal ArticleDOI
TL;DR: In this article, the authors used a well-established empirical rule on electrophilic substitution involving directing groups in organic chemistry, where two luminophores are covalently linked to benzene ortho, meta, and para to each other.
Abstract: The ability to modulate luminescence is crucial for organic light-emitting molecules. However, the correlation between molecular structure and emission is not always obvious and systematic. Here, using a well-established empirical rule on electrophilic substitution involving directing groups in organic chemistry, we present a model system, where two luminophores are covalently linked to benzene ortho, meta, and para to each other, to demonstrate that the rule can also be useful in predicting the fluorescence and phosphorescence behaviors of these disubstituted benzene molecules. The benzene ring works as a "molecular wire" that transduces electron density when the two luminophores form ortho- and para-isomers, while little to no transduction can be noted for the meta-isomer, based on well-established organic chemistry. We anticipate that many more "textbook examples" of electronic directing in organic chemistry can be used for systematic modulation of molecular fluorescence and room-temperature phosphorescence.

15 citations


Cited by
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01 Feb 1995
TL;DR: In this paper, the unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio using DFT, MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set.
Abstract: : The unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio. Harmonic force fields are obtained using Density Functional Theory (DFT), MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set. DFT calculations use the Local Spin Density Approximation (LSDA), BLYP, and Becke3LYP (B3LYP) density functionals. Mid-IR spectra predicted using LSDA, BLYP, and B3LYP force fields are of significantly different quality, the B3LYP force field yielding spectra in clearly superior, and overall excellent, agreement with experiment. The MP2 force field yields spectra in slightly worse agreement with experiment than the B3LYP force field. The SCF force field yields spectra in poor agreement with experiment.The basis set dependence of B3LYP force fields is also explored: the 6-31G* and TZ2P basis sets give very similar results while the 3-21G basis set yields spectra in substantially worse agreements with experiment. jg

1,652 citations

Journal ArticleDOI
TL;DR: In this article, the authors analyzed key photophysical processes related to triplet excitons, including intersystem crossing, radiative and non-radiative decay, and quenching processes.
Abstract: Triplet excitons in organic molecules underscore a variety of processes and technologies as a result of their long lifetime and spin multiplicity Organic phosphorescence, which originates from triplet excitons, has potential for the development of a new generation of organic optoelectronic materials and biomedical agents However, organic phosphorescence is typically only observed at cryogenic temperatures and under inert conditions in solution, which severely restricts its practical applications In the past few years, room-temperature-phosphorescent systems have been obtained based on organic aggregates Rapid advances in molecular-structure design and aggregation-behaviour modulation have enabled substantial progress, but the mechanistic picture is still not fully understood because of the high sensitivity and complexity of triplet-exciton behaviour This Review analyses key photophysical processes related to triplet excitons, including intersystem crossing, radiative and non-radiative decay, and quenching processes, to illustrate the intrinsic structure–property relationships and draw clear and integrated design principles The resulting strategies for the development of efficient and persistent room-temperature-phosphorescent systems are discussed, and newly emerged applications based on these materials are highlighted Advances in molecular-structure design and modulation of the aggregation behaviour have enabled much progress in the observation of room-temperature phosphorescence from organic aggregates This Review analyses key photophysical processes related to triplet excitons, illustrating the intrinsic structure–property relationships and identifying strategies to design efficient and persistent room-temperature-phosphorescent systems

552 citations

Journal ArticleDOI
TL;DR: A series of novel host-guest organic phosphors allowing dynamic color tuning from the cyan to orange red (608 nm) are developed, which can provide a crucial step towards the next-generation of security technologies for information handling.
Abstract: Organic materials with long-lived, color-tunable phosphorescence are potentially useful for optical recording, anti-counterfeiting, and bioimaging. Herein, we develop a series of novel host-guest organic phosphors allowing dynamic color tuning from the cyan (502 nm) to orange red (608 nm). Guest materials are employed to tune the phosphorescent color, while the host materials interact with the guest to activate the phosphorescence emission. These organic phosphors have an ultra-long lifetime of 0.7 s and a maximum phosphorescence efficiency of 18.2 %. Although color-tunable inks have already been developed using visible dyes, solution-processed security inks that are temperature dependent and display time-resolved printed images are unprecedented. This strategy can provide a crucial step towards the next-generation of security technologies for information handling.

259 citations

Journal ArticleDOI
TL;DR: A rational strategy toward amorphous smart luminophores with colorful, excitation-dependent, and time-dependent p-RTP, excellent solution processability, and film-forming ability for versatile applications is outlined.
Abstract: Achieving persistent room-temperature phosphorescence (p-RTP), particularly those of tunable full-colors, from pure organic amorphous polymers is attractive but challenging. Particularly, those with tunable multicolor p-RTP in response to excitation wavelength and time are highly important but both fundamentally and technically underexplored. Here, a facile and general strategy toward color-tunable p-RTP from blue to orange-red based on amidation grafting of luminophores onto sodium alginate (SA) chains, resulting in amorphous polymers with distinct p-RTP and even impressively excitation-dependent and time-dependent afterglows is reported. p-RTP is associated with the unique semi-rigidified SA chains, effective hydrogen bonding network, and oxygen barrier properties of SA, whereas excitation-dependent and time-dependent afterglows should stem from the formation of diversified p-RTP emissive species with comparable but different lifetimes. These results outline a rational strategy toward amorphous smart luminophores with colorful, excitation-dependent, and time-dependent p-RTP, excellent solution processability, and film-forming ability for versatile applications.

138 citations

Journal ArticleDOI
TL;DR: In this article, the authors review the recent progress in exploring nonconventional luminophores and discuss the current challenges and future perspectives, and highlight the clustering-triggered emission (CTE) mechanism, which emphasizes clustering of electron rich moieties and consequent electron delocalization along with conformation rigidification.
Abstract: Nonconventional luminophores devoid of remarkable conjugates have attracted considerable attention due to their unique luminescence behaviors, updated luminescence mechanism of organics and promising applications in optoelectronic, biological and medical fields. Unlike classic luminogens consisting of molecular segments with greatly extended electron delocalization, these unorthodox luminophores generally possess nonconjugated structures based on subgroups such as ether (–O–), hydroxyl (–OH), halogens, carbonyl (CO), carboxyl (–COOH), cyano (CN), thioether (–S–), sulfoxide (SO), sulfone (OSO), phosphate, and aliphatic amine, as well as their grouped functionalities like amide, imide, anhydride and ureido. They can exhibit intriguing intrinsic luminescence, generally featuring concentration-enhanced emission, aggregation-induced emission, excitation-dependent luminescence and prevailing phosphorescence. Herein, we review the recent progress in exploring these nonconventional luminophores and discuss the current challenges and future perspectives. Notably, different mechanisms are reviewed and the clustering-triggered emission (CTE) mechanism is highlighted, which emphasizes the clustering of the above mentioned electron rich moieties and consequent electron delocalization along with conformation rigidification. The CTE mechanism seems widely applicable for diversified natural, synthetic and supramolecular systems.

133 citations