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White LEDs were fabricated by precoating blue InGaN LEDs with blends of a green emitting polymer (Poly[{9,9-dioctyl-2,7-divinylenefluorenylene)-alto-co-(2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene}], PFPV) and a red emitting polymer (Poly[1-methoxy-4-(2-ethylhexyloxy-2,5-phenylenevinylene)], MEH-PPV), which acted as the phosphor. The two polymers were blended in different weight ratios, which were found to affect the green (555 nm) and red (610 nm) emission intensity. The CIE-1931 coordinate, T c and R a all changed as the MEH-PPV content increased. The white LED of the polymer blend phosphor containing 33 wt % MEH-PPV had a luminous efficiency of 54.2 lm/W at 20 mA with a CIE-1931 coordinate, T c and R a of (0.3328, 0.3547), 5488 and 71.4, respectively.

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Spherical cadmium sulfide (CdS) nanoparticles, 4 -5 nm in diameter, were synthesized using an aqueous cadmium nitride [Cd(NO 3 ) 2 . 4H 2 O] and sodium sulfide [Na 2 S . 9H 2 O] solution in a microemulsion system. The effects of the water to surfactant molar ratio (W = [water]/[surfactant]), the concentration of precursors, the Cd to S precursor ratio, and the density of the ultrasonic wave on the properties of the CdS nanoparticles were examined. The luminescent properties and the size effect of the nanoparticles were characterized using UV-vis absorption and photoluminescence (PL) spectra. The PL emission intensity did not change significantly with an increase in precursor and surfactant concentrations. The absorption edge and PL peak energy of the CdS nanoparticles shifted to shorter wavelengths with an increase in cadmium nitride concentration owing to a phase change and a decrease in CdS nanoparticle size.