Yuan-Chun Wu

Intermolecular Electronic Coupling of Organic Units for Efficient Persistent Room‐Temperature Phosphorescence

Abstract Although persistent room‐temperature phosphorescence (RTP) emission has been observed for a few pure crystalline organic molecules, there is no consistent mechanism and no universal design strategy for organic persistent RTP (pRTP) materials. A new mechanism for pRTP is presented, based on combining the advantages of different excited‐state configurations in coupled intermolecular units, which may be applicable to a wide range of organic molecules. By following this mechanism, we have developed a successful design strategy to obtain bright pRTP by utilizing a heavy halogen atom to further increase the intersystem crossing rate of the coupled units. RTP with a remarkably long lifetime of 0.28u2005s and a very high quantum efficiency of 5u2009% was thus obtained under ambient conditions. This strategy represents an important step in the understanding of organic pRTP emission.

An AEE-active polymer containing tetraphenylethene and 9,10-distyrylanthracene moieties with remarkable mechanochromism

A polymer (poly(9,10-anthracenevinylene-alt-4,4-(9,9-bis(4-(4-(1,2,2-triphenylvinyl)phenoxy)butyl)-9H-fluorene-2,7-diyl) dibenzaldehyde), P1 was successfully synthesized through the Wittig-Horner reaction by employing fluorene and 9,10-distyrylanthracene moieties as building blocks for backbone and tetraphenylethenes as pendant groups. Photophysical and thermal properties of the resulting polymeric emitter were fully characterized by ultraviolet-visible (UV-Vis) absorption and photoluminescence (PL) spectra, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). While P1 emits an orange-light centered at 567 nm in dilute tetrahydrofuran (THF) solution, the solid powder of the polymer exhibits strong yellow emission peaked at 541 nm. It is also found that the as-synthesized polymer shows unique property of aggregation-enhanced emission (AEE). In addition, P1 possesses high thermal stability with a decomposition temperature (Td,5% of 430 °C and high morphological stability with a glass transition temperature (Tg of 171 °C. Under the stimulus of mechanical force, the emission of P1 can be changed from yellow to red (Δλmax = 61 nm), showing a remarkable mechanochromism. The results from XRD analysis suggest that such mechanochromic phenomenonof P1 is probably caused by the destruction of crystalline structure, which leads to the conformational planarization of the distyrylanthracene moieties forming by the polymerization and the increase of molecular conjugation of the backbone.

Nitrogen-Doped Amorphous InZnSnO Thin Film Transistors With a Tandem Structure for High-Mobility and Reliable Operations

The threshold voltage shift (AVth) in amorphous InZnSnO thin-film transistors (a-IZTO TFTs) during negative gate-bias stress (NGBS) is significantly improved by nitrogen doping. Numerous N-In bonds eliminate donorlike subgap states near the Fermi level, which improve stability during stress but degrade electron mobility. We developed tandem TFTs with an a-IZTO:N layer on top of an a-IZTO layer, in which mobility reaches 31.76 ± 0.81 cm2/Vs and the reliability is improved. Especially, AVth in NGBS is reduced by 80% for pristine a-IZTO devices. This simple but an effective method achieves fast and reliable operation in the a-IZTO TFTs.

Integrating Poly-Silicon and InGaZnO Thin-Film Transistors for CMOS Inverters

The applications of a-InGaZnO thin-film transistors (TFTs) to logic circuits have been limited owing to the intrinsic n-channel operation. In this paper, we demonstrated a hybrid inverter constructed by p-channel low-temperature poly-silicon (LTPS) TFTs and n-channel amorphous-indium–gallium–zinc–oxide (a-IGZO) TFTs. Hydrogenated LTPS TFTs and a-IGZO TFTs have been successfully fabricated on the same panel, followed by a rapid thermal annealing treatment to remove the hydrogens in the a-IGZO TFTs. The resulted hybrid inverter exhibits large noise margin closed to

CCDC 1481207: Experimental Crystal Structure Determination

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Subgap State Engineering Using Nitrogen Incorporation to Improve Reliability of Amorphous InGaZnO Thin-Film Transistors in Various Stressing Conditions

and a high voltage gain as 68.3. Due to the complementary configurations in the static state, the inverter shows small current and thus consumes low power in hundreds of picowatts. As all the fabrication processes are compatible with conventional techniques, the reported results may open new opportunities in circuit design and applications for oxide TFTs.

Achieving remarkable mechanochromism and white-light emission with thermally activated delayed fluorescence through the molecular heredity principle

Related Article: Bingjia Xu, Haozhong Wu, Junru Chen, Zhan Yang, Zhiyong Yang, Yuan-Chun Wu, Yi Zhang, Chongjun Jin, Po-Yen Lu, Zhenguo Chi, Siwei Liu, Jiarui Xu, Matthew Aldred|2017|Chemical Science|8|1909|doi:10.1039/C6SC03038F

Achieving very bright mechanoluminescence from purely organic luminophores with aggregation-induced emission by crystal design

Instability of amorphous InGaZnO thin-film transistors (a-IGZO TFTs) remains an obstacle for commercialization. Here, we systematically discuss the effect of nitrogen incorporation on a-IGZO TFT stability and developed Ar/O2/N2 atmosphere to improve the stability under stressing in different conditions. Based on X-ray photoelectron spectrometer results, it is revealed that the positive gate bias stress (PGBS) stability is significantly improved due to microscopically passivated metal-oxygen bonds. Yet, the negative gate bias and light stress (NBLS) stability is seriously deteriorated with heavily nitrogen incorporation probably due to the bandgap narrowing effect. By optimizing a mixed O2/N2 atmosphere, the subgap states are finely tuned to afford optimal performance and stability. The developed IGZO TFTs exhibit mobility (12.67 cm2/Vs), small shift of threshold voltage under PGBS (reduced by 64% as compared with the pristine a-IGZO TFTs), and good negative gate bias stability and with NBLS stability as well.