Jun Ye

Management of Singlet and Triplet Excitons in a Single Emission Layer: A Simple Approach for a High‐Efficiency Fluorescence/Phosphorescence Hybrid White Organic Light‐Emitting Device

A high-efficiency single-emission-layer (EML) hybrid white organic light emitting device is fabricated based on an ideal sky-blue fluorophor, DADBT, using a novel doping concentration regulation strategy, which effectively separates and respectively utilizes the singlet and triplet excitons in the single-EML. The white device shows excellent electroluminescence performance with maximum total efficiencies of 26.6%, 53.5 cd A(-1) and 67.2 lm W(-1) .

Novel Efficient Blue Fluorophors with Small Singlet‐Triplet Splitting: Hosts for Highly Efficient Fluorescence and Phosphorescence Hybrid WOLEDs with Simplified Structure

The exact hosts for F-P hybrid WOLEDs have been first demonstrated following a new design strategy for blue fluorophors with small singlet-triplet splitting. Two novel compounds DPMC and DAPSF exhibit efficient blue fluorescence, high triplet energies and good conductivities. These merits allow us to use new simplified device designs to achieve high efficiency, slow efficiency roll-off and stable emission color.

Highly efficient non-doped deep-blue organic light-emitting diodes based on anthracene derivatives

Three deep-blue-emitting anthracene derivatives, 2-tert-butyl-9,10-bis(9,9-dimethylfluorenyl) anthracene (TBMFA), 2-tert-butyl-9,10-bis[4-(2-naphthyl)phenyl] anthracene (TBDNPA), and 2-tert-butyl-9,10-bis[4-(9,9-dimethylfluorenyl)phenyl] anthracene (TBMFPA), with naphthalene or 9,9-dimethylfluorene side units, have been designed, synthesized, and characterized. The anthracene derivatives show strong deep-blue emission both in solution and in thin films. The three derivatives also have high glass-transition temperatures (Tg ≥ 133 °C) due to the presence of sterically congested terminal groups. Organic light-emitting diodes (OLEDs) prepared using these anthracene derivatives as non-doped emitters exhibit bright and saturated deep-blue emissions. OLEDs based on TBDNPA give the best performance with a low turn-on voltage (3.0 V with a brightness of 1 cd m−2), and a high efficiency (5.17% external quantum efficiency at 8.4 mA cm−2). These results are among the best ever reported for saturated deep-blue OLEDs with a CIE coordinate of y < 0.10.

Aggregation-Induced Near-Infrared Absorption of Squaraine Dye in an Albumin Nanocomplex for Photoacoustic Tomography in Vivo

Photoacoustic tomography (PAT) is a newly emerging noninvasive imaging modality that could be further enhanced using near-infrared (NIR)-absorbing materials as contrast agents. To date, the most extensively studied photoacoustic imaging agents are inorganic nanomaterials because organic materials with NIR-absorption capabilities are limited. In this study, a NIR-absorbing nanocomplex composed of a squaraine dye (SQ) and albumin was prepared based on the aggregation-induced NIR absorption of SQ. Through aggregation, the absorption spectrum of SQ was widened from the visible-light region to the NIR region, which facilitated photoacoustic signal generation in the tissue-transparent NIR optical window (700-900 nm). Blood analysis and histology measurements revealed that the nanocomplex can be used for PAT applications in vivo without obvious toxicity to living mice.

Achieving Highly Efficient Simple-Emission Layer Fluorescence/Phosphorescence Hybrid White Organic Light-Emitting Devices via Effective Confinement of Triplets

Achieving high efficiencies in simple device configurations is a long-standing and meaningful target for organic light-emitting devices (OLEDs). Herein, by utilizing an efficient blue-violet fluorophor (CzS1) that has a high triplet energy of 2.62 eV, the significance of effective confinement of the green triplets in fluorescence/phosphorescence hybrid white devices (F/P-WOLEDs) that have highly simplified emission layers (EMLs) containing only RGB emitters was demonstrated. The non-p-i-n warm-white device exhibited excellent performance with a maximum forward power efficiency high up to 42.1 lm W(-1), and maintaining at 26.3 lm W(1-) at a practical luminance of 1000 cd m(-2).

Non-blinking, highly luminescent, pH- and heavy-metal-ion-stable organic nanodots for bio-imaging

Heavy-metal-free, organic-small-molecule-based fluorescent nanodots (Sdots, 31-60 nm in diameter) based on 2,7-di(4-(diphenylamino)phenyl-2,1,3-benzothiadiazol-7-yl)-9,9-spirobifluorene (Spiro-BTA) were prepared through a simple solution process. The Sdots show not only non-blinking and high-brightness fluorescence but also stability in various pH conditions and heavy metal ion solutions. More importantly, Spiro-BTA Sdots demonstrate obviously much higher brightness with very high signal-to-background ratio in Hela cell, compared with common CdSe/ZnS QDs. In addition, they exhibit large Stokes shifts, broad absorption spectra, and low toxicity to living cells which enable their applications as good fluorescence probes for bio-imaging. Further application of Sdots for folate receptor-mediated live-cell endocytosis was demonstrated by non-convalent modification with folic acid linked multidentate ligands.

A Bipolar Transporter as an Efficient Green Fluorescent Emitter and Host for Red Phosphors in Multi‐ and Single‐Layer Organic Light‐Emitting Diodes

Multifunctional donor-acceptor compound 4,4-bis(dibenzothiophene-S,S-dioxide-2-yl)triphenylamine (DSTPA) was obtained by linking a strongly electron-withdrawing core and a strongly electron-donating core with a biphenyl bridge in linear spatial alignment. DSTPA not only has suitable HOMO and LUMO levels for easily accepting both holes and electrons, it was also demonstrated to have a high fluorescence quantum yield of 0.98 and a high triplet energy level of 2.39 eV. Versatile applications of DSTPA for bipolar transport, green fluorescent emission, and sensitizing a red phosphor were systematically investigated in a series of multi- and single-layer organic light-emitting devices. In traditional multilayer devices, it shows excellent performance both in an undoped fluorescent device (used as a green emitter and achieving maximum current and power efficiencies (CE and PE) of 12.6 cd A(-1) and 9.4 Lm W(-1) , respectively) and in a red phosphorescent device (used as a host and achieving maximum CE and PE of 26.4 cd A(-1) and 26.3 Lm W(-1) , respectively). Furthermore, DSTPA was also simultaneously used as an emitter, a hole transporter, and an electron transporter in a single-layer device showing CE and PE of 5.1 cd A(-1) and 4.7 Lm W(-1) , respectively. A single-layer red phosphorescent device with efficiencies of 11.7 cd A(-1) and 12.6 Lm W(-1) was obtained by doping DSTPA with a red phosphor. The performances of all of the devices in this work are comparable to the best of their corresponding classes in the literature.

A reticuloendothelial system-stealthy dye–albumin nanocomplex as a highly biocompatible and highly luminescent nanoprobe for targeted in vivo tumor imaging

A reticuloendothelial system (RES)-stealthy nanoprobe for enhanced tumor imaging is a longstanding pursuit. In this study, a nanocomplex comprising albumin and dye is assembled without crosslinker use. The nanocomplex shows intense luminescence with a photoluminescence quantum yield of up to 0.39 and a large Stokes shift of >130 nm. The nanocomplex also exhibits higher stability against hydrolysis than indocyanine green during the 14 days test. The nanocomplex shows favourable high biocompatibility and can be used for cell labelling. Remarkably, the nanocomplex exhibits six times higher tumor accumulation than that in the liver and spleen. At 96 h post-injection, the nanoprobe is still observable and gives a clear imaging of tumors, which can help in convenient diagnosis post-injection.