For electroluminescence with delayed fluorescence, the azasiline unit has been introduced for the first time as a donor in a thermally activated delayed fluorescence (TADF) material. The TADF material (DTPDDA) shows strong intramolecular charge transfer (CT) character with large spatial separation with the acceptor of triazine leading to narrow splitting of singlet and triplet excited states for the efficient reverse intersystem crossing (RISC). A blue organic light emitting diode (OLED) based on DTPDDA not only displays deep blue in the Commission Internationale de L’Eclairage (CIE) coordinates of (0.149, 0.197) but also exhibits a high external quantum efficiency (EQE) of 22.3% which is the highest value ever reported for a blue fluorescent OLED. Theoretical prediction based on transient photoluminescence (PL) and optical simulation result agrees well with the achieved EQE indicating the successful conversion of triplet excitons to singlet in the blue fluorescent OLED by using DTPDDA.

With the goal of achieving high-performance electrically stable organic field-effect transistors (OFETs), we chemically graft a fluorinated polymer nanolayer onto the polar oxide dielectric surfaces via a simple and easy fabrication process in ambient air. The para-fluorine-thiol click reaction between poly(pentafluorostyrene) (PFS) and mercaptopropyltrimethoxysilane is used to synthesize a graftable fluorinated polymer (gPFS). The surface characteristics of the gPFStreated SiO 2 dielectrics and the crystal structure and grain growth of the overlying organic semiconductors are investigated. Various semiconductor materials are employed for the OFETs prepared with gPFS-treated SiO 2 dielectrics, including vacuum-processed pentacene, N,N-ditridecyl-3,4,9,10-perylenetetracarboxylic diimide, solution-processed 5,11-bis-(triethylsilylethynyl)anthradithiophene, and poly[2,5-bis(2-octyldodecyl)pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione-(E)-1,2-di-(2,2′-bithiophen-5-yl)ethane. Three OFETs are prepared with different dielectrics: (i) bare SiO 2 , (ii) gPFS-treated SiO 2 , and (iii) perfluorooctyltriethoxysilane-treated SiO 2 . The OFETs prepared with the gPFS-treated SiO 2 dielectrics display the highest mobilities and smallest hysteresis. Furthermore, the gPFS-treated SiO 2 provides the best device stability under a sustained gate bias, suggesting that the gPFS surface minimize the number of traps present in the OFET.

Pseudo-regular alternating PDPP-TVS copolymers using an asymmetric monomer (thiophene-vinylene-selenophene (TVS)) are synthesized. Unlike regular alternating copolymers, these polymers are highly soluble in nonchlorinated solvents such as tetra-hydrofuran, toluene, xylene, and tetralin. The organic field-effect transistor devices fabricated using these polymers dissolved in nonchlorinated solvents exhibit a high hole mobility up to 8.2 cm(2) V(-1) s(-1).

We describe several strategies for the molecular design of high-efficiency blue fluorescent emitters. Asymmetric donor–acceptor (D–A) and symmetric A–D–A-type fluorescent emitters were designed with spiroacridine donors and diphenyltriazine acceptors. Substituting a toluene or xylene moiety for the phenyl group connecting the donor and acceptor and replacing the diphenylsilane group with a fluorene moiety resulted in a deeper blue emission without any losses in luminescence efficiency. On the basis of these substitutions, deep blue organic light emitting diodes (OLEDs) with Commission Internationale de L’Eclairage (CIE) coordinates of (0.149, 0.082) and an external quantum efficiency (EQE) of 7.7% were fabricated using a D–A-type emitter. Symmetrizing the D–A structure to an A–D–A structure increased the proportion of horizontally oriented emission dipoles in the organic film from 70 to 90%. OLEDs incorporating symmetric A–D–A-type emitters had EQEs as high as 8.5% due to increased outcoupling efficiencies and also showed deep blue emission with CIE coordinates of (0.142, 0.116). The molecular design strategies described herein can be applied to donor–acceptor-type fluorescent emitters for the fabrication of efficient deep blue OLEDs.

the heteroleptic molecular structure of the Ir (III) complexes and strong Coulombic interaction between the dopant and host molecules are the driving forces of the preferred EDO. [ 4,5 ] In this regard, the structure of the emitting molecules, as well as the organic host molecules, must infl uence the EDO. The effect of the ancillary ligands in the heteroleptic Ir complexes (HICs) on the EDO and the photoluminescence quantum yields (PLQY) in doped fi lms were reported recently, exhibiting that bis(phenyl-pyridine)Ir III (2,2,6,6-tetramethylheptane-3,5-diketonate) (Ir(ppy) 2 tmd) results in higher PLQY and Θ values than Ir(ppy) 2 acac, which in turn has higher values than Ir(ppy) 3 . Unfortunately, the reason why different ancillary ligands resulted in different EDOs has not been reported yet and their discussion was limited to rather qualitative description and there are few reports on the quantitative and systematic investigation of the effect of the structure of the emitting molecules on the EDO in fi lms. Furthermore, the effect of the main ligands in HICs has not been investigated up to now to our best knowledge. The understanding of the structure-property relationship will eventually lead us to identify phosphorescent dyes with high Θ in fi lms to fabricate OLEDs with high EQE.In this study, we investigated the effect of main ligands of HICs on the EDO in doped fi lms and related the EDO to the angle between the TDM of emission dipoles and the C 2 axis of the molecules. For this purpose, we designed and synthesized four iridium complexes where the hydrogen atom(s) at different positions of the cyclometalated ligands of Ir(ppy) 2 tmd were systematically replaced by methyl group(s) keeping the ancillary ligand the same as tmd. We used the same host for the dopants to minimize the host effect, i.e., to minimize the variation of the intermolecular interaction between the dopants and the host. We found that the methyl substitution resulted in different directions of the TDM in the iridium complexes. Moreover, the molecules with higher angle between the C 2 axis and the TDM in the molecules resulted in a higher horizontal portion of the emitting dipole orientation in the emitting layer. Based on the observation, we were able to develop a new green emitter having high Θ of 80% and PLQY of 97% and resultantly demonstrate a green OLED exhibiting an unprecedented high EQE of 34.1%, power effi ciency (PE) of 157.6 lm W −1 , and current effi ciency (CE) of 120.5 cd A −1 using the new emitter.Chemical structures of the green-emitting phosphorescent dyes investigated in this study are shown in Figure 1 a. All the structures are based on Ir(ppy) 2 tmd having high Θ and