Green-Light-Emitting Poly(Spirobifluorene)s with an Electron-Rich Unit in the Side Chain and an Electron-Deficient Unit in the Main Chain

Abstract

Poly(spirobifluorene)s and their derivatives with three primary colors are promising for application in efficient and stable polymer light-emitting diodes (PLEDs). Here, a novel approach is reported to tune the emission colors of blue-light-emitting poly(spirobifluorene) s through a charge-transfer mechanism from the side chain to the main chain. By using the electron-rich 2,3,6,7-tetra-octyloxyfluorene unit as the side chain and incorporating the electron-deficient dibenzothiophene-S,S-dioxide (SO) unit into the main chain, a series of polyspirobifluorene derivatives are successfully developed. They all display efficient green photoluminescence and electroluminescence. The observed green emission can be ascribed to both intramolecular and intermolecular charge transfer from the pendant 2,3,6,7-tetra-octyloxyfluorene unit to the SO unit in the main chain. Single-layer PLEDs of these polymers reveal a maximum luminance efficiency of 1.99 cd A(-1) and a maximum power efficiency of 1.30 lm W-1 with Commission Internationale de L'Eclairage coordinates of (0.37, 0.54)