New Iridium Complexes as Highly Efficient Orange–Red Emitters in Organic Light‐Emitting Diodes

Abstract

nanoparticles into a hexagonal array, while maintaining the photoluminescence of the nanoparticles. This patterning technique illustrates a simple example of directed deposition where the lateral distribution of the nanoparticles in a thin film can be manipulated rapidly by use of a capillary force. This deposition process is quite versatile since both the size of the nanoparticles and the diameter of the nanopores can easily be changed. In addition, if symmetric copolymers are used, where the morphology is lamellar as opposed to cylindrical, then an assembly of the nanoparticles into nanoscopic channels can be attained. Further, if an electron beam were used to crosslink the PS and degrade the PMMA, then a pattern could be written on the surface and nanoparticles of one size could be selectively placed within the exposed pattern. Subsequent exposure of this film to e-beam or UV radiation would allow the placement of nanoparticles with a different diameter to be placed elsewhere on the surface, resulting in the fabrication of a patterned heterogeneous structure. Furthermore, by placing appropriate functionality on the ligands attached to the nanoparticles, we will be able to impart favorable interactions between the particles and the bottom of the pores to further enhance the deposition process. The simplicity, generality, versatility, and speed of this deposition process make it amenable to the fabrication of complex structures and to large-scale commercial processes. ExperimentalNanoparticle Preparation: Cadmium selenide (CdSe) nanoparticles were prepared according to literature procedures, following the method of Peng and coworkers [25]. Nanoparticles of various diameters were prepared, all of which were capped with an organic shell of phosphorous-containing surfactants, such as tri-n-octylphosphine oxide (TOPO). These hydrophobic nanoparticles could be readily dissolved or dispersed in common organic solvents used in these experiments.Template Preparation: Templates were prepared by anchoring a random copolymer of PS and PMMA containing 58 % styrene onto a silicon wafer onto which a 60±100 nm layer of SiO was evaporated; the coated templates were then annealed for 3 days. Non-anchored random copolymer was rinsed from the surface, and a very thin film of P(S-b-MMA) diblock copolymer with a thickness of L 0 was spin-coated onto this surface, then annealed at 170 C overnight. The film was then exposed to UV light under vacuum, and immersed in glacial acetic acid to selectively remove the degraded PMMA from the PS matrix. Subsequent inspection by atomic force microscopy (AFM) showed hexagonally ordered cylindrical pores normal to the substrate. These templates were then dipped vertically into heptane solutions of nanoparticles at various nanoparticle concentrations. The withdrawal rates varied from fast (~1200 cm min ±1 ) to slow (~2 cm min ±1 ). The impregnated templates were cut into small pieces, and removed from the silicon wafer by etching and floating on 5 % HF in water. The templates were retrieved with a ...

Solution-Processed Blue/Deep Blue and White Phosphorescent Organic Light-Emitting Diodes (PhOLEDs) Hosted by a Polysiloxane Derivative with Pendant mCP (1,3-bis(9-carbazolyl)benzene)

“…[53][54][55][56][57] This confirms that the polysiloxane backbone has only minimal influence on the photophysical properties of the pendant mCP chromophore. The triplet energy (E T ) of PmCPSi was obtained from its phosphorescence spectrum at 77 K in dichloromethane: a well-structured band is observed in the 400-550 nm region.…”

Synthesis, Diastereomer Separation, and Optoelectronic and Structural Properties of Dinuclear Cyclometalated Iridium(III) Complexes with Bridging Diarylhydrazide Ligands

“…[44][45][46] In diiridium complexes, which incorporate conjugated bridging ligands, theoretical calculations often predict that a degree of frontier orbital character is localized on the bridging unit. 23,26,29,32,35,[37][38][39][40]42 In these cases a highly flexible bridge is expected to promote nonradiative processes and weaken emission.…”

The Efficient Green Emitting Iridium(III) Complexes and Phosphorescent Organic Light Emitting Diode Characteristics

“…A promising phosphorescent metal complex should have a short lifetime in the excited state and high phosphorescent efficiency for the highly efficient OLEDs. Among the various phosphorescent emitters, iridium complexes remain the most effective material due to their ability to achieve maximum internal quantum efficiency, nearly 100%, and high external quantum efficiency in the devices (O'Brien et al 2003;Duan et al 2003;Xie et al 2001;Noh et al 2003;Wang et al 2001;Neve et al 2001). The most widely used homoleptic green emitting iridium(III) complex, fac-tris(2-phenylpyridine)iridium [Ir(ppy) 3 ], derivatives have shown a number of advantages such as ease of tuning emission energy by functionalizing the 'ppy' ligand with electron donating and electron withdrawing substituents and high phosphorescent quantum efficiency at room temperature Jung et al 2004;Lee et al 2009).…”