Guozhu Ren

Changchun Institute of Applied Chemistry

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Liang Zhou

Chinese Academy of Sciences

Yitong Sun

Shandong University

Long Tian

Chinese Academy of Sciences

Danyang Zhang

Changchun Institute of Applied Chemistry

Y. Xu

University of Science and Technology of China

Shihong Zhou

Institute of Acoustics

Danyang Zhang

Changchun Institute of Applied Chemistry

Shihong Zhou

Chinese Academy of Sciences

Tingyu Pan

Changchun Institute of Applied Chemistry

Qingxia Wang

Chinese Academy of Sciences

Cooperative Institutions

Chinese Academy of Sciences

Changchun Institute of Applied Chemistry

University of Science and Technology of China

University of Chinese Academy of Sciences

Shanghai Jiao Tong University

Sichuan University

Fujian Institute of Research on the Structure of Matter

East China Normal University

Ministry of Agriculture and Rural Affairs

Ocean University of China

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One-step solvothermal synthesis of Na-doped carbon quantum dots and concomitant photochromic small molecules

Chemical Physics Letters (2024)

Yitong Sun Danyang Zhang Guozhu Ren Shihong Zhou Long Tian

Carbon Quantum Dots

Carbon fibers

10.1016/j.cplett.2024.141114

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Citations (3)

A Novel Near-Infrared Ytterbium Complex [Yb(DPPDA)2](DIPEA) with Φ = 0.46% and τobs = 105 μs

Molecules (2023)

Guozhu Ren Danyang Zhang Hao Wang Xiaofang Li Ruiping Deng

The luminescent performances of near-infrared (NIR) lanthanide (Ln) complexes were restricted greatly by vibration quenching of X-H (X = C, N, O) oscillators, which are usually contained in ligands and solvents. Encapsulating Ln3+ into a cavity of coordination atoms is a feasible method of alleviating this quenching effect. In this work, a novel ytterbium complex [Yb(DPPDA)2](DIPEA) coordinated with 4,7-diphenyl-1,10-phenanthroline-2,9-dicarboxylic acid (DPPDA) was synthesized and characterized by FT-IR, ESI-MS and elemental analysis. Under the excitation of 335 nm light, [Yb(DPPDA)2](DIPEA) showed two emission peaks at 975 and 1011 nm, respectively, which were assigned to the characteristic 2F5/2 → 2F7/2 transition of Yb3+. Meanwhile, this ytterbium complex exhibited a plausible absolute quantum yield of 0.46% and a luminescent lifetime of 105 μs in CD3OD solution. In particular, its intrinsic quantum yield was calculated to be 12.5%, and this considerably high value was attributed to the near-zero solvent molecules bound to Yb3+ and the absence of X-H oscillators in the first coordination sphere. Based on experimental results, we further proposed that the sensitized luminescence of [Yb(DPPDA)2](DIPEA) occurred via an internal redox mechanism instead of an energy transfer process.

Ytterbium

Quantum yield

Coordination sphere

10.3390/molecules28041632

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One-Step Solvothermal Synthesis of Na-Doped Carbon Quantum Dots and Concomitant Photochromic Small Molecules

Yitong Sun Danyang zhang Guozhu Ren Shihong Zhou Long Tian

Hydrothermal method is a common way to synthesize carbon quantum dots (CQDs), but perplexing by-products are non-negligible shortcoming. The small molecules associated with CQDs synthesis have drawn more attentions because of their luminescent property. In this work, Na-doped CQDs with excellent photoluminescent property as well as small molecules 4,4'-diaminoazobenzene with photochromism characteristic were prepared based on p-phenylenediamine and sodium hydroxide via one-step solvothermal method. The photoluminescence of as-synthesized Na-doped CQDs is tremendously influenced by H+ ions, and CQDs-O- Na+ structure existing in Na-doped CQDs was verified. At the same time, photochromism which was owing to by-product 4,4'-diaminoazobenzene with photochromic was observed and investigated. The absorption spectrum of 4,4'-diaminoazobenzene overlaps markedly with the photoluminescence spectrum of Na-doped CQDs and thus result in fluorescence internal filtering effect, by which the fluorescence cause interesting photochromism phenomenon. Furthermore, compared with conventional synthetic route of 4,4'-diaminoazobenzene, this method has the advantages of simplicity and metal-free.

Carbon Quantum Dots

Carbon fibers

Solvothermal synthesis

10.2139/ssrn.4592794

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Bright Blue Light‐Emitting Diodes Based on Well‐Modified Carbon Dots by Designing Co‐Host Systems to Balance Carriers’ Injection

Advanced Optical Materials (2023)

Danyang Zhang Jingyu Wang Jiaxuan Yin Guozhu Ren Ruixia Wu

Abstract Leveraging bright and stable carbon dots (CDs) for blue light‐emitting diodes (LEDs) is a prospective but challenging topic. Aggregation‐caused quenching (ACQ) of CDs and device engineering of CDs‐LEDs are two issues. Here, blue CDs with quantum yield of 59.75% are synthesized. Hydrogen bonds increase rigidity and facilitate luminescence, while polymer chains increase spatial resistance and resist ACQ. Then, solution‐processed blue CDs‐LEDs are assembled by blending CDs into poly(N‐vinylcarbazole) (PVK) as light‐emitting layer (EML). Furthermore, several other materials are also employed as the second host to reduce injection barrier, facilitate carriers’ transport, and balance carriers’ distribution. In particular, the blue CDs‐LED based on the co‐host system of PVK and 4‐[1‐[4‐[bis(4‐methylphenyl)amino]phenyl]cyclohexyl]‐N‐(3‐methylphenyl)‐N‐(4‐methylphenyl)benzenamine (TAPC) achieves a maximum brightness up to 827.60 cd m −2 . This work is a step forward for applying CDs in LEDs.

Quantum yield

10.1002/adom.202300075

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Citations (8)

Polymerized Carbon Dots with Broad Emission and Suppressed Aggregation‐Caused Quenching Effect Toward Electroluminescent White Light‐Emitting Diodes

Advanced Optical Materials (2024)

Danyang Zhang Tingyu Pan Jingyu Wang Yitong Sun Guozhu Ren

Abstract Carbon dots (CDs) possess intrinsically broad emission spectra, making them suitable for modulating high‐quality white light‐emitting diodes (WLEDs). However, the chief technical challenge in applying CDs to WLEDs is the aggregation‐caused quenching (ACQ) effect. A common solution is polymer post‐modification on the surface of CDs, which is a low‐yield, hard‐to‐purified, and complicated process. Herein, polymerized CDs with broad emission (full width at half maxima, FWHM = 187 nm) are synthesized via a one‐step solvothermal method. The obtained polymerized CDs display excellent solution‐processed and film‐forming capabilities, with absolute photoluminescence quantum yield as high as 4.7% in thin film state, creating a firm foundation for assembling solution‐processed WLEDs. Moreover, the polymerization steps of CDs are analyzed and described in detail. The polymer chains prevent ACQ and create new energy levels, resulting in the broad emission of CDs in an aggregated state. Subsequently, WLEDs are fabricated using polymerized CDs as the single active emitting material. The optimal device achieves the maximum brightness of 337.50 cd m −2 and FWHM of 242 nm, covering nearly the entire visible spectral window. The results present a new approach to obtaining polymerized CDs and further fabricating WLED with a straightforward, cost‐effective method.

Quantum yield

10.1002/adom.202401128

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Citations (2)

White Organic Light‐Emitting Diodes with External Quantum Efficiency of 20.77% at 10000 cd m⁻² and Ultra‐High Color Stability by Controlling Exciton Distribution

Small (2024)

Haoran Yang Weidong Sun Yufu Sun J. Wang Xiaoyang Xia

Abstract Although brightness and efficiency have been continually improved, the inability to achieve superior efficiency, color stability, and low‐efficiency roll‐off simultaneously in white organic light‐emitting diodes (OLEDs) remains a knotty problem restricting the commercial application. In this paper, emission balance for two different horizontal orientation emitting molecules is maintained by using hole transport materials and bipolar host materials to control carriers’ recombination and exciton diffusion. Impressively, the obtained devices exhibit extremely stable white emission with small chromaticity coordinates variation of (0.0023, 0.0078) over a wide brightness range from 1000 to 50000 cd m −2 . Meanwhile, the optimal white OLED realizes the power efficiency, current efficiency, and external quantum efficiency up to 70.68 lm W −1 , 85.53 cd A −1, and 24.33%, respectively at the practical brightness of 1000 cd m −2 . Owing to reduced heterogeneous interfaces and broadening recombination region, this device exhibits a high EQE over 20% under high luminance of 10000 cd m −2 , demonstrating slight efficiency roll‐off. The operating mechanism of the device is analyzed by versatile experimental and theoretical evidences, which concludes precise manipulation of charges and excitons is the key points to achieve these excellent performances. This work provides an effective strategy for the design of high‐performance white OLEDs.

Quantum Efficiency

Chromaticity

Electrical efficiency

10.1002/smll.202403345

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Facile Post‐Processing Approach to Modulate Fluorescent Properties and New Matrix‐Assisted Method to Achieve Solid‐State Luminescence of CDs Based on CTAB Surfactant

Advanced Optical Materials (2025)

Qingxia Wang Danyang Zhang Tingyu Pan Guozhu Ren Y. Xu

Abstract To realize the practical application of carbon dots (CDs), it is crucial to devise straightforward techniques that can finely modulate the fluorescent properties of CDs. Apart from that, it is imperative to weaken the aggregation‐caused quenching (ACQ) effect, which poses a significant challenge to the utilization of solid‐state CDs. In this work, three CDs named as CDs‐1, CDs‐2, and CDs‐3 are synthesized, and the fluorescence tuning of these CDs is successfully realized, assisted by cetyltrimethylammonium bromide (CTAB) surfactant, because its unique molecular structure is conducive in bolstering fluorescence intensity and adjusting emission wavelength. Furthermore, the luminescence of solid‐state CDs is successfully achieved by employing CTAB as substrate in the matrix‐assisted synthesis of composites CDs‐1@CTAB, CDs‐2@CTAB, and CDs‐3@CTAB. Notably, the photoluminescence quantum yield (PLQY) of CDs‐2@CTAB reaches an impressive value as high as 79.31%, surpassing the value of 70.29% obtained by pristine CDs‐2. The experimental results reveal that CDs@CTAB composites exhibit intriguing afterglow characteristics including room temperature phosphorescence (RTP) and thermally activated delayed fluorescence (TADF). This work confirms the versatility of CDs and highlights the significance of surfactant‐assisted strategies in improving the performance of CDs.

Matrix (chemical analysis)

10.1002/adom.202403381

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Efficient Organic Light-Emitting Diodes Obtained by Introducing Gadolinium (Gd) Complexes Based on Pyrazolone Derivative Ligands as Hole Trappers

ACS Applied Materials & Interfaces (2024)

Y. Xu Tingyu Pan Guozhu Ren Jingyu Wang Haoran Yang

The utilization of lanthanide (Ln) complexes in the realm of organic light-emitting diodes (OLEDs) has garnered extensive interest, particularly in their role as luminescent materials or electron trappers. A series of gadolinium (Gd) complexes with energy levels of high HOMO/LUMO and different triplet state energies were designed and synthesized by introducing substituents with different electronic effects onto the pyrazolone derivative ligands. Subsequently, these complexes were precisely purified by vacuum sublimation and codoped into the light-emitting layer (EML) of the OLEDs. This process was facilitated through the well-matched HOMO/LUMO levels and triplet energies among various functional materials. Consequently, the maximum external quantum efficiencies of blue, red, and green OLEDs were simultaneously enhanced with the ratios of 119%, 28%, and 71%, respectively. This improvement can be credited to the introduction of Gd(III) complex molecules within EMLs, which helps to capture excess holes and improve carriers' balance.

Pyrazolones

Derivative (finance)

10.1021/acsami.4c14821

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