Non-doped Blue Devices Research Articles

Multifunctional zig-zag-shaped D-π-A-π-D emitters with high conjugation extent for blue FOLEDs and host for PHOLEDs

We have synthesized zig-zag shaped, meta- and para-linked D-π-A-π-D blue emitters, m-BTPAPy and p-BTPAPy based on a non-symmetrical connection strategy of two identical π-conjugated groups. The phenanthrimidazole moiety coupled to pyridine via naphthyl spacer by para- and meta-linking modes. Both m-BTPAPy (Td/Tg, °C: 564/281) and p-BTPAPy (Td/Tg, °C: 502/246) exhibit excellent thermal stability and can form a stable amorphous film. Changing the connection strategy from para to meta mode, m-BTPAPy shows deep blue emission with CIE (0.15, 0.07). The highly twisted m-BTPAPy exhibit higher Photoluminescence quantum yield (PLQY)s/f of 0.98/0.85 than p-BTPAPy (0.95/0.80) owing to the suppression of intermolecular stacking. The non-doped blue device (BOLEDs) with multifunctional m-BTPAPy/p-BTPAPy show external quantum efficiency (EQE) of 7.12/5.12% with small roll-off efficiency of 1.68/2.14%, power efficiency (PE) of 5.92/5.42 lm/W, the luminance of 58675/76234 cd/m2, and current efficiency (CE) of 6.12/5.86 cd/A. The non-doped device using m-BTPAPy/p-BTPAPy as both emitting and electron-transporting material exhibit luminance of 40671/49539 cd/m2, CE of 5.01/5.08 cd/A, PE of 4.68/4.76 lm/W, EQE of 6.12/4.81%, roll-off efficiency of 1.63/1.87%, and CIE (0.15, 0.10)/(0.15, 0.11). These bipolar materials with high triplet energy were employed as hosts in green and red PhOLEDs. The green (m-BTPAPy: Ir(ppy)3)/red device (m-BTPAPy: Ir(MDQ)2(acac)) exhibit maximum EQE of 29.85/20.09%, luminance of 79523/42412 cd/m2, CE of 78.62/27.56 cd/A, and PE of 72.36/23.86 lm/W, and CIE (0.33, 0.60)/(0.65,0.33).

A triphenylacrylonitrile phenanthroimidazole cored butterfly shaped AIE chromophore for blue and HLCT sensitized fluorescent OLEDs

The non-doped blue device with TPATPA-CNPPI shows luminance of 15 892 cd m−2, CE of 19.58 cd A−1, PE of 17.84 lm W−1, EQE of 8.96%, EUE of 73.40% and small roll-off efficiency (RO) of 1.11%.

Efficient Non-doped Blue Fluorescent Organic Light-Emitting Diodes Based on Anthracene-Triphenylethylene Derivatives.

The development of efficient blue materials has been a continuous research topic in the field of organic light-emitting diodes (OLEDs). In this paper, three aggregation-induced emission enhancement active blue emitters, PIAnTPE, TPAAnTPE and CzAnTPE, are successfully synthesized by attaching a triphenylethylene unit and phenanthroimidazole/triphenylamine/carbazole moieties to the 9,10-positions of anthracene, respectively. The three compounds exhibit good thermal stabilities, appropriate for the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) energy levels and display high photoluminescence quantum yields (PLQYs) of 65, 70 and 46 % in the solid state. Non-doped blue devices using PIAnTPE, TPAAnTPE and CzAnTPE as the emitting layers show good electroluminescent performances, with the maximum external quantum efficiencies (EQEs) of 4.46, 4.13 and 4.04 %, respectively. More importantly, EQEs of all the three devices can be still retained when the luminescence reaches 1000 cd m-2 , exhibiting quite small efficiency roll-offs in the non-doped OLEDs.

Excimer-emitting single molecules with stacked π-conjugated groups covalently linked at the 1,8-positions of naphthalene for highly efficient blue and green OLEDs

Two efficient blue-light-emitting compounds, 1,8-bis(4-(N-carbazolyl)phenyl)naphthalene (BCzPN) and 1,8-bis(4-(10-phenylanthracen-9-yl)-phenyl)naphthalene (BPAPN), are designed and synthesized, in which two phenylcarbazole or diphenylanthracene units are closely stacked through bonding to the 1- and 8-positions of the naphthalene ring, resulting in strong intramolecular excimer emissions in solution or as a film. By utilizing BPAPN as an emitter, high efficiencies of 6 cd A−1 and 5.8% external quantum efficiency (EQE) at 100 cd m−2, and 8 cd A−1 and 5.8% EQE at 1000 cd m−2 are achieved in a non-doped blue device. By using BCzPN or BPAPN as a host, a DPAVBi-doped BCzPN based blue device gave high efficiencies of 15 cd A−1 and 6.5% EQE at 100 cd m−2, and 12 cd A−1 and 5.5% EQE at 1000 cd m−1, and a C545T-doped BPAPN based green device gave high efficiencies of 23 cd A−1 and 6.7% EQE at 100 cd m−2, and 22 cd A−1 and 6.7% EQE at 1000 cd m−2, respectively.