Exploiting A Dual-fluorescence Process In Fluorene-dibenzothiophene-s,s-dioxide Co-polymers To Give Efficient Single Polymer Leds With Broadened Emission

摘要

A description of the synthesis of random (9,9-dioctylfluorene-2,7-diyl)-(dibenzothiophene-S,S-dioxide-3,7-diyl) co-polymers (p(F-S)x) by palladium-catalyzed Suzuki cross-coupling polymerization where the feed ratio of the latter is varied from 2 to 30 mol % (i.e., x = 2 - 30) is given. Polymer light emitting devices are fabricated with the configuration indium tin oxide/ poly(3,4-ethylenedioxythiophene):poly(styrenesulfonic acid)/p(F-S)x/Ba/Al. The device external quantum efficiency increased as the ratio of the S co-monomer was increased, up to a maximum of 1.3% at 100 mA cm~(-2) for p(F-S)30 and a brightness of 3 770cd m~(-2) (at 10V). The S units impart improved electron injection, more balanced mobilities, and markedly improved device performance compared to poly(9,9-dioctylfluorene) under similar conditions. These co-polymers display broad emission, observed as greenish-white light, which arises from dual fluorescence, viz. both local excited states and charge transfer states. Utilizing dual emission can reduce problems associated with Foerster energy transfer from high-energy to-low energy excited states.