A novel bipolar hosting material, 11-(3-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl)-12,12-dimethyl-11,12-dihydroindeno[2,1-a]carbazole (DPDDC), was designed, synthesized, and characterized for green phosphorescent organic light-emitting diodes (PhOLEDs). The DPDDC exhibits excellent hole and electron transport properties, superior thermal stability, a high glass-transition temperature and a small singlet-triplet energy gap for efficient reverse intersystem crossing from triplet to singlet, reducing the triplet density of the host for PhOLEDs. The electrophosphorescence properties of the devices using DPDDC as the host and three green phosphorescent iridium(III) complexes, bis(2-(4-tolyl)pyridinato-N,C2′)iridium(III) acetylacetonate, bis(2-phenylpyridine)iridium(III) acetylacetonate, and bis(4-methyl-2,5-diphenylpyridine)iridium(III) acetylacetonate [(mdppy)₂Iracac] as the emitter were investigated. The green PhOLED with 5 wt% (mdppy)₂Iracac presents an excellent performance, including a high power efficiency of 92.3 lm W⁻¹, high external quantum efficiency of 23.6%, current efficiency roll-off as low as 5.5% at 5000 cd m⁻² and a twentyfold lifetime improvement (time to 90% of the 5000 cd m⁻² initial luminance) over the reference electrophosphorescent device.

A fiber-shaped polymer light-emitting electrochemical cell (PLEC) was developed by sandwiching an electroluminescent polymer layer between two aligned carbon nanotube (CNT) sheet electrodes. Similar to a conventional planar PLEC, the electroluminescent polymer layer and two carbon nanotube electrodes are closely and stably contacted, so that the injected charges can be rapidly and efficiently transported. Due to their one-dimensional structure, the fiber-shaped PLEC demonstrates unique and promising advantages, e.g., the luminance is almost independent on the observation angle. In addition, the fiber-shaped PLEC is thin, lightweight and flexible, which bespeaks a promising future for various electronic textiles.

Organic semiconductors as a promising class of optoelectronic materials have attracted significant interest because of their fascinating physical–chemical properties, simple fabrication scheme to afford wearable or flexible devices, much wider scopes for easy production, and shaping and tuning of semiconductor properties compared to inorganic materials, such as silicon (Si).^1,2 At present, a number of organic semiconductor classes based on small molecules and polymers have been discovered and widely used for next-generation organic and hybrid optoelectronics, such as organic thin film transistors, organic photodiodes, organic solar cells, and organic light-emitting diodes (OLEDs).^{3 – 5}

By adjusting the conjugation degrees of the phenylquinoline-based cyclometalated ligands, yellow, orange to red phosphorescent iridium(III) complexes [Ir(bzq)₂(POXD)] (1, bzq = 7,8-benzoquinoline, POXD = N-(5-phenyl-1,3,4-oxadiazol-2-yl)-diphenylphosphinic amide), [Ir(pq)₂(POXD)] (2, pq = 2-phenylquinoline) and [Ir(piq)₂(POXD)] (3, piq = 1-phenylisoquinoline) have been designed and prepared. Their photophysical and electrochemical studies and theoretical calculations were performed, and [Ir(bzq)₂(POXD)] was also determined by X-ray crystallography. At room temperature, complexes 1–3 exhibit efficient phosphorescence emissions at about 539, 592 and 614 nm with photoluminescence quantum yields (PLQYs) of 0.21, 0.06 and 0.06 in CH₃CN solutions, respectively. In the 5 wt% doped poly(methyl methacrylate) (PMMA) film, the PLQYs (0.35 for complex 1, 0.37 for complex 2 and 0.18 for complex 3, respectively) increase significantly. Organic light emitting diodes (OLEDs) based on these complexes were fabricated to evaluate their potential application. The yellow device in the configuration ITO/2-TNATA (25 nm)/NPB (5 nm)/TCTA (10 nm)/complex 1 (10 wt%):mCP (10 nm)/complex 1 (10 wt%):TPBi (10 nm)/TPBi (40 nm)/Liq (1 nm)/Al (100 nm) shows excellent performance with a maximum luminance of 24 080 cd m⁻², maximum current efficiencies of 70.1 cd A⁻¹ and maximum external quantum efficiencies of 21.3% along with low efficiency roll-off.

High-performance MoS ₂ nanopillar arrays characterized with electron injection and light extraction were facilely developed and applied in flexible inverted OLEDs.