Yu-Lin Chu

A New Supramolecular Hole Injection/Transport Material on Conducting Polymer for Application in Light-Emitting Diodes

A new DNA-mimetic π-conjugated polymer poly(triphenylamine-carbazole) (PTC-U) has been prepared which exhibits high thermal stability, non-corrosion, excellent hole injection and electron-blocking abilities in the solid state owing to the uracil induced physical cross-linking. In addition, a trilayer device with PTC-U as a hole injection/transport layer is approximately 1.6 times higher than that of the commercial product PEDOT:PSS-based devices.

A new supramolecular POSS electroluminescent material

A new polyhedral oligomeric silsesquioxane (POSS) core star-like supramolecular blue-light electroluminescent material, 4-uracilbutyl-1-methylpyrene ether (U-PY)/octakis[dimethyl(N-(6-acetamidopyridin-2 yl))siloxy] silsesquioxane (ODAP-POSS) has been synthesized. This U-PY/ODAP-POSS contains eight pyrene chromophore arms formed through complementary uracil-diamidopyridine (U-DAP) pairs and exhibits high quantum efficiencies and good solution processing properties. The photoluminescence spectra of U-PY/ODAP-POSS (50/50) reveal that the color is stable after heating the sample at 150 °C for 1 h, in contrast, the pyrene/ODAP-POSS (50/50) shows significant thermal quenching. An electroluminescence (EL) device based on U-PY/ODAP-POSS exhibits higher maximum brightness and higher luminance efficiency relative to that of the U-PY. In addition, U-PY/ODAP-POSS also behaves as an effective dopant that enhances energy transfer from itself to MEH-PPV. The U-PY/ODAP-POSS-doped MEH-PPV blends exhibit high luminance efficiency, 1.45 times greater than MEH-PPV.

Bioinspired hole-conducting polymers for application in organic light-emitting diodes

A novel uracil-functionalized poly(3-thiophene) as a hole-injecting/transporting layer in an organic light-emitting device is able to form physical crosslinkages resulting in high thermal stability, non-corrosion, excellent hole injection/transport and electron-blocking capabilities in the solid state, and it achieves up to 10 times higher performance than that of conventional poly(3-thiophene)s under similar experimental conditions.

A new benzoxazine containing uracil, complementary functionality

A new benzoxazine, uracil containing benzoxazine (UBz), has been successfully synthesized. The FTIR and DSC measurement of the poly(UBz)/poly(BA-a) blends indicated that hydrogen bonding interactions between uracil groups would result in a decrease in the exothermic peak temperature. In addition, the PL measurement confirmed that the poly(UBz)/poly(BA-a) blend possessed complementary behavior.

Large-scale production of ureido-cytosine based supramolecular polymers with well-controlled hierarchical nanostructures

A novel supramolecular polymer containing urea-cytosine (UrCy) quadruple hydrogen-bonding moieties that possesses a high association constant (Ka > 106 M−1) was synthesized at high yield (96%) at kilogram-scale. The synthesized telechelic macromer dissolved in solution can undergo a substantial change in solution viscoelasticity and can self-assemble due to the noncovalent nature of supramolecular polymerization. As the concentration of UrCy in solution was increased, the spherical assemblies gradually transformed to an ordered lamellar phase with an extremely high degree of polymerization. In addition, the dynamic behavior of UrCy units induced a sudden phase transition in the bulk state, revealing an interesting order–disorder transition from a crystalline solid to liquid state. This newly-discovered material has excellent polymer-like features that are distinct to existing systems. A simple path for forming supramolecular polymers is recommended for the design, large-scale production and manipulation of self-assembled materials with distinctive properties.

A solvent-resistant azide-based hole injection/transporting conjugated polymer for fluorescent and phosphorescent light-emitting diodes

Interfacial mixing of polymers is a critical issue when attempting to improve the charge transport and stabilize the operation of solution-processed organic light-emitting diodes (OLEDs). Herein, we describe a simple methodology for overcoming interfacial mixing, based on the use of a photo-crosslinkable hole injection/transporting material (HITM). We synthesized a conjugated polymer, PTCAzide, bearing ready crosslinking ability and investigated its suitability for use as an HITM. Photo-crosslinking of the PTCAzide copolymer gave X-PTCAzide, which exhibited much higher thermal stability (the glass transition temperature increased by 21 K relative to that of PTCAzide), remarkable electrochemical stability, and excellent solvent-resistance, thereby expanding the operation time of corresponding electronic devices. Such a tris(8-hydroxyquinolinato)aluminum-based trilayer device reached a maximum brightness of 52971 cd m−2, and the maximum luminance efficiency (LE) and power efficiency (ηE) are both higher than those of the corresponding device based on commercial PEDOT:PSS. In addition, a solution-processed phosphorescent OLED device incorporating X-PTCAzide also exhibited good performance (external quantum efficiency: 7.93%; LE: 29.6 cd A−1; ηE: 14.3 lm W−1; maximum brightness: 34484 cd m−2). The efficient and simple photocrosslinking without adding an initiator could facilitate the fabrication process. Thus, PTCAzide appears to be a promising next-generation HITM for the development of highly efficient and inexpensive OLEDs. Its photo-crosslinkable nature allows improvements in morphological stability and hole injection/transporting ability, leading to more stable devices with better operation, without disrupting molecular packing or charge transport.