A new green electroluminescence polymer, CN-poly(dihexylfluorenevinylene) (CN-PDHFV), which denotes poly [(9,9-, was synthesized by condensation polymerization utilizing the Knoevenagel reaction. The resulting polymer exhibits good solubility in common organic solvents such as chloroform, THF, and ODCB. The polymer is also easily cast on a glass plate to green film. The UV-vis spectrum of the polymer exhibits characteristically a broad absorption band at 440 nm. This polymer shows photoluminescence around λ max ) 535 nm (exciting wavelength 410 nm) and green electroluminescence around λmax ) 530 nm. The current-voltage-luminance (I-V-L) characteristics of the polymer show a turn-on voltage of 4.8 V and a brightness of 600 cd/m 2 at 5.

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Two different upconversion mechanisms leading to green fluorescence in an Er3+ doped LiNbO3 crystal have been investigated with pulse laser excitations at the wavelengths of 1064 and 980 nm. In the case of the 1064 nm pump, the Er3+ ions become excited by the phase-matched second harmonic wave generated in the LiNbO3 crystal, whereas sequential two-photon absorption is mainly responsible for the excitation with the 980 nm pump. The second harmonic excitation is of an order of magnitude more efficient than the sequential two photon excitation in the upconversion of the near-infrared pump photons to the green fluorescence.

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