Junwu Chen

Blue organic light-emitting diode based on 1,2,3,4,5-pentaphenyl-1-(8-phenyl-1,7-octadiynyl)silole

A new silole derivative, 1,2,3,4,5-pentaphenyl-1-(8-phenyl-1,7-octadiynyl)silole, is synthesized, characterized, and used as the electron-transport/emission layers in organic light-emitting diodes. Blue emission at 492 nm is observed, with a maximum luminance of 10 460 cd/m/sup 2/ at 18 V. The respective maximum current and power efficiencies are 8.47 cd/A and 3.8lm/W. A triple-layer composite cathode was used, consisting of tris(8-hydroxy-quinolne)aluminum (Alq/sub 3/) lithium fluoride and aluminum. The dependence of emission efficiency on the thickness of TPD and Alq/sub 3/ is investigated and explained.

Synthesis, thermal stability, and light-emitting properties of hyperbranched poly(phenylenegermolene)s

A germole-containing diacetylene, 1,1-diethynyl-2,3,4,5-tetraphenylgermole (2), was synthesized. Homopolymerization of 2 and its copolycyclotrimerization with 1-octyne were effected by TaCl5–Ph4Sn in toluene, producing completely soluble polymers (1) in moderate yields. The molecular structure of 1 was characterized by spectroscopic methods. The thermal stability of 1 was evaluated by thermogravimetric analysis, which detected virtually no weight loss when the polymers were heated to ∼350°C. These hyperbranched polymers were electronically conjugated as suggested by their strong absorption in the visible spectral region (λmax∼540 nm). Photoluminescence of the polymers was dramatically enhanced by cooling their solutions to low temperatures. Restricted intramolecular rotations of the phenyl rings upon the axes of the single bonds linked to the germole cores at the cryogenic temperatures might be responsible for this unique phenomenon of cooling-enhanced emission.

UNUSUAL ELECTRONIC AND PHOTONIC BEHAVIORS OF LINEAR POLY(SILOLYLACETYLENE)S AND HYPERBRANCHED POLY(SILOLYLENEARYLENE)S

A series of dendritic 2,3,4,5-tetraphenylsiloles (1–8) are prepared. Polymerizations of 4-8 are effected by transition-metal catalysts, giving linear (9-12) and hyperbranched polymers (14) in high yields. Whereas the silole polymers are practically nonluminescent when molecularly dissolved, they become emissive when aggregated in poor solvents or cooled to low temperatures. The light-emitting diodes using linear poly(silolylacetylene)s as active layers emit blue and green lights with current efficiency up to 1.45 cd/A. The hyperbranched poly(silolenearylene)s are nonlinear optically active and strongly attenuate the optical power of intense laser pulses, whose optical limiting performances are superior to that of C60, a well-known optical limiter.

P-76: Efficient and Bright OLED based on Hexaphenylsilole

OLED devices based on hexaphenylsilole (HPS) have been fabricated. These devices emit very bright greenish-blue light, up to 55,880cd/m2 at 16V. Emission starts at 2.6V, and reaches 100- cd/m2 and 10,790-cd/m2 at 5V and 10V respectively. The maximum electroluminescence (EL) efficiency and power efficiency are 20-cd/A and 12.8-lm/W, respectively. The maximum external quantum efficiency is 7%.

Generalized mixed mode reflective liquid crystal displays for three‐panel color projection applications

The general parameter space was introduced for generalized mixed mode reflective liquid crystal displays (RLCDs). A contrast ratio parameter space was also derived to provide a better picture of both the voltage-off and voltage-on states. A guideline for the optimization of RLCD modes in terms of high light efficiency and high contrast at low operating voltage is given. Such features are important for reflective displays, particularly for crystalline silicon based RLCDs. As a result, we find a number of new RLCD modes with high contrast and high brightness, which are quite suitable for the three-panel color projection system.

Very bright and efficient OLED based on hexaphenylsilole

OLED devices based on hexaphenylsilole (HPS) have been fabricated. These devices emit very bright greenish-blue light, up to 55880 cd/m/sup 2/ at 16 V. Emission starts at 2.6 V, and reaches 100-cd/m/sup 2/ and 10790-cd/m/sup 2/ at 5 V and 10 V respectively. The maximum electroluminescence (EL) efficiency and power efficiency are 20-cd/A and 12.8-lm/W, respectively. The maximum external quantum efficiency is 7%.