|Title:||High-efficiency pure blue thermally activated delayed fluorescence emitters with a preferentially horizontal emitting dipole orientation: Via a spiro-linked double D-A molecular architecture||Authors:||Ni, Fan
Lee, Wei Kai
Pan, Kuan Chung
|Issue Date:||1-Jan-2019||Journal Volume:||7||Journal Issue:||35||Source:||Journal of Materials Chemistry C||Abstract:||
© 2019 The Royal Society of Chemistry. Blue as one of the three primary colors is of great significance for lighting and full-color displays, and the development of blue emitters with satisfactory color purity and high efficiency is still a formidable challenge for organic light-emitting diodes (OLEDs). In this study, a spiro-linked double donor-acceptor (D-A) molecular architecture is introduced to selectively improve the horizontal emitting dipole orientation of blue emitters and thereby boost the electroluminescence (EL) performance of blue OLEDs. To testify the validity, a thermally activated delayed fluorescence (TADF) emitter, namely SBA-2DPS, is designed by connecting two D-A pairs with a sp3 hybrid carbon atom. Compared to the prototypical emitter DMAC-1DPS, the shape of SBA-2DPS is elongated dramatically without expanding the degree of π-conjugation owing to the σ-spacer linkage. Consequently, a high horizontal dipole ratio (Θv = 87%) is achieved for SBA-2DPS. Besides, SBA-2DPS exhibits high thermal stability, pure blue emission and distinct TADF characteristics. OLEDs based on SBA-2DPS exhibit an external quantum efficiency (ηext) of 25.5% and favorable Commission International de l'Eclairage (CIE) coordinates of (0.15, 0.20). Such an inspiring performance is rationalized by their high out-coupling efficiency (Φout = 38.2%) and the optical microcavity effect. Unambiguously, this finding demonstrates the validity of the spiro-linked double D-A molecular architecture in constructing good blue TADF emitters with a preferentially horizontal emitting dipole orientation for high-efficiency blue OLEDs.
|Appears in Collections:||電機工程學系|
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