Optical Properties of Oligo(9,9-diarylfluorene) Derivatives in Thin Films and Their Application for Organic Light-Emitting Field-Effect Transistors

We demonstrated that oligo(9,9-diarylfluorene) derivatives have high potential for optoelectronic applications such as organic lasers and light-emitting organic field-effect transistors (LE-OFETs). The oligo(9,9-diarylfluorene) derivatives have high photoluminescence quantum efficiencies up to ΦPL ≈ 70−75% and very low amplified spontaneous emission thresholds (Eth) down to 0.5 μJ/cm2 in their vacuum-deposited neat films. In particular, the trimer derivatives (B3 and T3) show higher ΦPL and lower Eth than those of the dimers (B2 and T2). Efficient deep-blue LE-OFETs with the electroluminescence (EL) peaking at λpeak = 429 nm were demonstrated using the ter(9,9-diarylfluorene) as the active layer. Rather high luminance up to L ≈ 150 cd/m2 and EL quantum efficiency up to ηext ≈ 0.60% were achieved with the optimum source-drain channel length, indicating bipolar carrier injection in the terfluorene layer under the FET operation.