High luminescent efficiency in light-emitting polymers due to effective exciton confinement

Highly efficient light-emitting polymers have become possible by molecular engineering. Photoluminescence (PL) quantum yield above 90% in the solid state is reported for the alternating block copolymer of distyrylbenzene. We conclude that the alternate arrangement of conjugated and nonconjugated segments with surrounding side groups for chromophores effectively confine the excitons for radiative emission. The effectiveness of the exciton confinement is confirmed through the temperature independence of the PL quantum yield. The time-resolved PL decay measurement supports this model through the independence of the PL yield on temperature and emission wavelength. The synthesized copolymers have been employed for the fabrication of electroluminescent (EL) devices, demonstrating high external EL efficiency with low operation threshold. (C) 2000 American Institute of Physics. [S0003-6951(00)03405-7].