Quantum dot light-emitting diode with quantum dots inside the hole transporting layers.

We report a hybrid, quantum dot (QD)-based, organic light-emitting diode architecture using a noninverted structure with the QDs sandwiched between hole transporting layers (HTLs) outperforming the reference device structure implemented in conventional noninverted architecture by over five folds and suppressing the blue emission that is otherwise observed in the conventional structure because of the excess electrons leaking towards the HTL. It is predicted in the new device structure that 97.44% of the exciton formation takes place in the QD layer, while 2.

Improved performance of organic light-emitting diodes with MoO3 interlayer by oblique angle deposition.

We fabricated and demonstrated improved organic light emitting diodes (OLEDs) in a thin film architecture of indium tin oxide (ITO)/ molybdenum trioxide (MoO3) (20 nm)/N,N'-Di(naphth-2-yl)-N,N'-diphenyl-benzidine (NPB) (50 nm)/ tris-(8-hydroxyquinoline) (Alq3) (70 nm)/Mg:Ag (200 nm) using an oblique angle deposition technique by which MoO3 was deposited at oblique angles (θ) with respect to the surface normal. It was found that, without sacrificing the power efficiency of the device, the device current efficiency and external quantum efficiency were significantly enhanced at an oblique deposition angle of θ=60° for MoO3.

Synthesis, characterization, and bipolar transporting behavior of a new twisted polycyclic aromatic hydrocarbon: 1',4'-diphenyl-naphtho-(2'.3':1.2)-pyrene-6'-nitro-7'-methyl carboxylate.

An asymmetric twistacene, 1',4'-diphenyl-naphtho-(2'.3':1.2)-pyrene-6'-nitro-7'-methyl carboxylate (tetracene 2), was synthesized by using benzyne-trapping chemistry.

Observation of excitonic quenching by long-range dipole-dipole interaction in sequentially doped organic phosphorescent host-guest system.

We studied the quenching mechanisms responsible for the low efficiency of thin film phosphorescence by a specially designed organic light-emitting diode with an emission layer consisting of a few repeating cells made of a sequentially evaporated host and guest. Variation of the thickness of the guest layer in each cell enables the study of the effect of molecule aggregation on the quantum efficiency. On the other hand, variation of the thickness of the host layer reveals a new long-range quenching mechanism involving a Förster-like dipole-dipole interaction.