Statistical copolymers for blue-light-emitting diodes

Fluorene-based statistical copolymers with m- and p-divinylbenzene were syn thesized by the Heck reaction to fabricate blue-light-emitting diodes (LEDs ). Photoluminescence (PL) spectra of the copolymers showed the maximum at 4 75 nm regardless of the concentration ratios between m- and p-divinylbenzen e to reveal the complete energy transfer from the chromophore with the meta unit to the fluorophore of the para unit while 100% of the meta unit exhib ited the emission maximum at 430 mo. The highest PL intensity was obtained with the ratio of 7/3 between the meta and pars units, However, the time-re solved picosecond fluorescence study on the polymer solution revealed that the intramolecular energy transfer alone in the copolymers was incomplete t o suppress the emission at 430 nm. The electroluminescence (EL) center of t he copolymers was the same as that of the PL to show the maximum at 475 nm. The highest-quantum efficiency of a single-layered LED fabricated with the light emissive copolymer with 30% of the para unit was observed to be 0.04 %, which would be improved by optimization of the device characteristics.