Department Physics and Astronomy and London Centre for Nanotechnology, University College London, London, WC1H 0AH, UK.
Advent Technologies SA Patras Science Park, Patra, 26504, Greece.
Sci Rep. 2017 May 9;7(1):1611. doi: 10.1038/s41598-017-01785-2.
We take advantage of a recent breakthrough in the synthesis of α,β-unfunctionalised 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) moieties, which we symmetrically conjugate with oligothienyls in an unexpectedly stable form, and produce a "metal-free" A-D-A (acceptor-donor-acceptor) oligomer emitting in the near-infrared (NIR) thanks to delocalisation of the BODIPY low-lying lowest unoccupied molecular orbital (LUMO) over the oligothienyl moieties, as confirmed by density functional theory (DFT). We are able to retain a PL efficiency of 20% in the solid state (vs. 30% in dilute solutions) by incorporating such a dye in a wider gap polyfluorene matrix and demonstrate organic light-emitting diodes (OLEDs) emitting at 720 nm. We achieve external quantum efficiencies (EQEs) up to 1.1%, the highest value achieved so far by a "metal-free" NIR-OLED not intentionally benefitting from triplet-triplet annihilation. Our work demonstrates for the first time the promise of A-D-A type dyes for NIR OLEDs applications thereby paving the way for further optimisation.
我们利用最近在α，β-未官能化的 4,4-二氟-4-硼-3a,4a-二氮杂-s-茚（BODIPY）部分合成方面的突破，以出乎意料的稳定形式将其与寡噻吩对称共轭，并产生一种“无金属”的 A-D-A（受体-供体-受体）寡聚物，由于 BODIPY 低占据最低未占据分子轨道（LUMO）在寡噻吩部分上的离域，通过密度泛函理论（DFT）证实其在近红外（NIR）区域发射。通过将这种染料掺入更宽能隙的聚芴基质中，我们能够在固态下保持 20%的 PL 效率（在稀溶液中为 30%），并证明了发射波长为 720nm 的有机发光二极管（OLED）。我们实现了高达 1.1%的外部量子效率（EQE），这是迄今为止通过非故意受益于三重态-三重态湮灭的“无金属”NIR-OLED 获得的最高值。我们的工作首次证明了 A-D-A 型染料在 NIR-OLED 应用中的前景，从而为进一步优化铺平了道路。
