Ionogels are good candidates for flexible electronics owing to their excellent mechanical and electrical properties, including stretchability, high conductivity, and stability. In this study, conducting ionogels comprising a double network (DN) of poly(N‐isopropylacrylamide‐co‐N,N′‐diethylacrylamide)/chitosan which are further reinforced by the ionic and covalent crosslinking of the chitosan network by tripolyphosphate and glutaraldehyde, respectively, are prepared. Based on their excellent mechanical properties and high conductivity, the developed DN ionogels are envisioned as stretchable ionic conductors for extremely stretchable alternating‐current electroluminescent (ACEL) devices. The ACEL device fabricated with the developed ionogel exhibits stable working operation under an ultrahigh elongation of over 1200% as well as severe mechanical deformations such as bending, rolling, and twisting. Furthermore, the developed ACEL devices also display stable luminescence over 1000 stretch/release cycles or at temperatures as harsh as 200 °C.

Recently, bipolar host materials are the most promising candidates for achieving high performance phosphorescent organic light-emitting diodes (PHOLEDs) in order to maximize recombination efficiency. However, the development of host material with high triplet energy (E T ) is still a great challenge to date to overcome the limitations associated with the present PHOLEDs. Herein, a highly efficient donor-π-acceptor (D-π-A) type bipolar host (4′-(9H-carbazol-9-yl)-2,2′-dimethyl-[1,1′-biphenyl]-4-yl)diphenylphosphine oxide (m-CBPPO) comprising of carbazole, 2,2′-dimethylbiphenyl and diphenylphosphoryl as D-π-A unit, respectively, is developed. Interestingly, a high E T of 3.02 eV is observed for m-CBPPO due to highly twisted conformation. Furthermore, the new host material is incorporated in PHOLEDs as emissive layer with a new carbene type Ir(cb) 3 material as a deep-blue emitter. The optimized devices show an excellent external quantum efficiency (EQE) of 24.8%with a notable Commission internationale de l'éclairage (x, y) ≤ 0.15, (0.136, 0.138) and high electroluminescence performance with extremely low efficiency roll-off. Overall, the above EQE is the highest reported for deep-blue PHOLEDs with very low efficiency roll-off and also indicate the importance of appropriate host for the development of high performance deep-blue PHOLEDs.

Deep‐blue triplet emitters remain far inferior to standard red and green triplet emitters in terms of exhibiting high‐color‐purity Commission International de l'Éclairage (CIE) y values of ≤0.1, external quantum efficiencies (EQEs), and high electroluminescent brightnesses in phosphorescent organic light‐emitting diodes. In fact, no deep‐blue triplet emitter with color purity and high device performance has previously been reported. In this study, a deep‐blue triplet emitter, mer‐tris(N‐phenyl, N‐benzyl‐pyridoimidazol‐2‐yl)iridium(III) (mer‐Ir1) is developed, which meets the requirements of the National Television System Committee (NTSC) CIE(x, y) coordinates of (0.149, 0.085) with an extremely high EQE of 24.8% and maximum brightness (Lmax) of 6453 cd m−2, by a device with a 40 vol% doping ratio. Moreover, another device demonstrates an EQEmax of 21.3%, an Lmax of 5247 cd m−2, and CIE(x, y) coordinates of (0.151, 0.086) at a 30 vol% doping ratio. This is the first report of a high‐performance, deep‐blue phosphor, carbene‐based Ir(III) complex device with outstanding CIE(x, y) color coordinates and a high EQE. The results of this study indicate that the novel dopant mer‐Ir1 is a promising candidate for reducing power consumption in display applications.

No abstract

Although several donor polymers have been synthesized for use in nonfullerene organic solar cells (NFOSCs), the number of efficient π‐conjugated donor polymers compatible with nonhalogenated solvent‐processed thick active layer NFOSCs is limited. Two wide‐bandgap π‐conjugated donor polymers functionalized with a siloxane side chain, P1 (chlorine‐free) and P2 (chlorinated), are designed and synthesized. The siloxane‐functionalized side chains and/or Cl π‐conjugated donor polymers increase the absorption coefficients, reduce the energy losses, increase the charge‐carrier mobility, and suppress the bimolecular recombination, which are beneficial to achieve high‐performance thick‐film ternary NFOSCs. Toluene‐processed devices based on P2:IT‐4F:BTP‐4Cl, and P2:IT‐4F:BTP‐4F exhibit high power conversion efficiencies (PCEs) of 13.25% and 11.02% with fill factors (FFs) of 70.03% and 71.60%, respectively. A P2:IT‐4F binary NFOSC exhibits a PCE of 10.38% with an FF of 69.78%, lower than that of the ternary NFOSC. The ternary device PCE of 13.25% is achieved using a 300 nm‐thick active layer, indicating that the siloxane‐functionalized side‐chain π‐conjugated polymer easily controls the bulk heterojunction blend film thickness of the NFOSC. The findings may potentially aid the development of nonhalogenated solvent‐processed thick‐film ternary NFOSCs that can satisfy future production requirements.