Optically active chemical defects in polyfluorene-type polymers and devices

Abstract

Polyfluorenes and polyfluorene-type polymers have emerged as a promising class of emitter materials for realizing blue polymeric light-emitting devices. However, during device operation material degradation leads to the occurrence of an unwanted green emission band at 2.2-2.3 eV. This chapter reviews the latest scientific investigations on the origin of this low energy emission band, putting special focus on chemical (i.e., keto defect sites, hydroxy-terminated polyfluorenes, etc.) and interface defects. Along this line, the formation of defect sites during polymer synthesis, their enhancement in the solid state upon, e.g., thermal stress, and the defect emission under device operation are discussed. Finally, novel approaches for realizing stable blue emitter materials are included, demonstrating that a thorough consideration of the herein presented results in materials design paves the way to polyfluorene-type polymers suitable for practical applications. © Springer-Verlag.