University Grants Committee

About: University Grants Committee is a government organization based out in Hong Kong, Hong Kong, China. It is known for research contribution in the topics: Organic semiconductor & Dendrimer. The organization has 34 authors who have published 51 publications receiving 2356 citations.

Soluble and Stable N‐Heteropentacenes with High Field‐Effect Mobility

Abstract: Organic thin-fi lm transistors (OTFTs) are essential building blocks of large-area, fl exible, and low-cost organic electronics and offer promising applications in technology areas, such as light-weight and fl exible displays; radio-frequency identifi cation (RFID) circuitry; [ 1 ] and physical, chemical, and biological sensors. [ 2 ] The ultimate success of OTFTs requires developing organic semiconductors that allow 1) effi cient charge transport, which is characterized by high fi eld-effect mobility; 2) solution-based processing for low-cost fabrication; and 3) good operational stability of devices under ambient air, moisture, and light exposure. [ 3 ] Although the fi eld-effect mobilities of leading organic semiconductors in OTFTs have reached or even exceeded the value of amorphous silicon ( ≈ 1 cm 2 V − 1 s − 1 ), organic semiconductors that can meet all the above requirements are still rare. [ 4 ] Such challenge is particularly true for n-type (electron-transporting) organic semiconductors. [ 5 ] In fact the development of n-type organic semiconductors for OTFTs has lagged behind that of p-type ones, primarily due to the inherent instability of organic anions in the presence of air and water and problems with oxygen trapping within these materials. [ 4a ]

The Position of Nitrogen in N‐Heteropentacenes Matters

Abstract: An exploratory study on novel silylethynylated N-heteropentacenes, which have their N atoms on the terminal rings of the pentacene backbone, is reported. This study leads to both p- and n-channel organic thin-film transistors with high field-effect mobility and also reveals that the position of the N atoms plays an important role in tuning the structures and properties of organic semiconductors based on N-heteropentacenes.

Curved Polycyclic Aromatic Molecules That Are π-Isoelectronic to Hexabenzocoronene

Abstract: Reported here are two types of curved π-molecules that are π-isoelectronic to planar hexabenzocoronene (HBC) but are forced out of planarity either by an embedded seven-membered ring or by atom crowding at the fjord region. Embedding a heptagon in HBC leads to a novel saddle-shaped molecule 1, whose π-backbone is slightly less curved than the previously reported [7]circulene in terms of the average Gauss curvature, but surprisingly much more rigid than [7]circulene. Overcrowded fjord regions in novel derivatives of hexabenzoperylene (HBP) 2a,b lead to both chiral twisted and antifolded conformers. The successful synthesis of 1 and 2a,b is related to introducing alkoxyl groups to unprecedented positions of hexaphenylbenzenes. It is found that the red twisted isomer of 2b isomerizes at elevated temperature to the yellow anti-folded conformer. This finding along with the study on the thermodynamics and kinetics of the thermal isomerization has improved the early understandings on the conformation of HBP. In ...

Electron Mobility Exceeding 10 cm(2) V(-1) s(-1) and Band-Like Charge Transport in Solution-Processed n-Channel Organic Thin-Film Transistors.

Abstract: Solution-processed n-channel organic thin-film transistors (OTFTs) that exhibit a field-effect mobility as high as 11 cm(2) V(-1) s(-1) at room temperature and a band-like temperature dependence of electron mobility are reported. By comparison of solution-processed OTFTs with vacuum-deposited OTFTs of the same organic semiconductor, it is found that grain boundaries are a key factor inhibiting band-like charge transport.

White Organic Light-Emitting Diodes with Evenly Separated Red, Green, and Blue Colors for Efficiency/Color-Rendition Trade-Off Optimization

Abstract: A novel yellowish-green triplet emitter, bis(5-(trifluoromethyl)-2-p-tolylpyridine) (acetylacetonate)iridium(III) (1), was conveniently synthesized and used in the fabrication of both monochromatic and white organic light-emitting diodes (WOLEDs). At the optimal doping concentration, monochromatic devices based on 1 exhibit a high efficiency of 63 cd A−1 (16.3% and 36.6 lm W−1) at a luminance of 100 cd m−2. By combining 1 with a phosphorescent sky-blue emitter, bis(3,5-difluoro-2-(2-pyridyl)phenyl)-(2-carboxypyridyl)iridium(III) (FIrPic), and a red emitter, bis(2-benzo[b]thiophen-2-yl-pyridine)(acetylacetonate)iridium(III) (Ir(btp)2(acac)), the resulting electrophosphorescent WOLEDs show three evenly separated main peaks and give a high efficiency of 34.2 cd A−1 (13.2% and 18.5 lm W−1) at a luminance of 100 cd m−2. When 1 is mixed with a deep-blue fluorescent emitter, 4,4′-bis(9-ethyl-3-carbazovinylene)-1,1′-biphenyl (BCzVBi), and Ir(btp)2(acac), the resulting hybrid WOLEDs demonstrate a high color-rendering index of 91.2 and CIE coordinates of (0.32, 0.34). The efficient and highly color-pure WOLEDs based on 1 with evenly separated red, green, blue peaks and a high color-rendering index outperform those of the state-of-the-art emitter, fac-tris(2-phenylpyridine)iridium(III) (Ir(ppy)3), and are ideal candidates for display and lighting applications.