Highly-efficient blue phosphorescent light-emitting diodes were fabricated based on a conjugated-polymer host by doping bis(2-(4,6-difluorophenyl)-pyridinato-N,C2') picolinate(FIrpic) into poly(9,9-dioctylfluorene)(PFO).Previously,conjugated polymers were not considered as potential hosts for blue phosphorescent dyes because of their low-lying triplet energy levels.Energy back transfer would occur and lead to poor luminescent efficiency in both photoluminescence(PL) and electroluminescence(EL) processes.However,by inserting a hole-transporting layer of poly(N-vinylcarbazole)(PVK),the energy back transfer was suppressed.At low FIrpic-doping concentrations,PFO emissions were completely quenched;with 8 wt% FIrpic,a maximum luminous efficiency of 11.5 cd/A was achieved.
A new kind of organic-inorganic hybrid HfO 2/SiO 2 sol-gel material with a large thermo-optic coefficient and a wide linear tunable temperature range has been developed for fabrication of a long period waveguide grating (LPWG) filter,whose parameters were optimized and designed by using finite difference time domain (FDTD) simulations.The LPWG filter,a periodic rectangle-corrugated grating structure,was easily fabricated with soft-lithography technique.At a temperature range from 19°C to 70°C,the fabricated LPWG filter element demonstrated a high temperature sensitivity of about 6.5 nm/°C and a wide linear tunable temperature range of 51°C,so that it can be used as a precise thermometer.Our results are useful for the designs of LPWG filters for the implementation of a wide range of thermo-optic functions.
In order to promote the light output powers of GaN-based light emitting diodes (LEDs), two kinds of novel corrosive liquidshave been developed in this paper to roughen the surface of the indium tin oxide (ITO) current spreading layer of LEDs. As aresult, the textured transparent ITO layer greatly enhanced the external quantum efficiency of the LEDs. Provided that a wafersample was dipped in a kind of corrosive liquid developed by us for only about 60 s, the light output powers of the LEDs canbe promoted by 24.7%, compared with conventional GaN-based LEDs. It is obvious that the presented method is simple, rapidand cost-effective.
