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Emitters displaying thermally activated delayed fluorescence (TADF) can lead to highly efficient organic light-emitting diodes (OLEDs). Such emitters are usually incorporated into the emissive layer (EML) at a relatively low concentration (

A scheme that allows stable confinement of a weakly ionized non‐neutral plasma is discussed. The method requires the forced rotation of the neutral gas within the trap about an axis that roughly coincides with the trap’s magnetic and mechanical axes. A number of the basic equilibrium and nonequilibrium properties of such a trapped plasma are calculated.

A family of photorefractive polymer composites has been developed that enable high-performance device operation at a wavelength of 975nm. This constitutes a major extension into the near-infrared spectral region for the operation of all-organic photorefractive devices. Utilizing our photorefractive materials, we demonstrate large net two-beam coupling gain of more than 100cm−1, 60% diffraction efficiency in four-wave mixing experiments, and a fast response time of 33ms, at an irradiance of 1W∕cm2.

Precise control of the electrical characteristics of organic field-effect transistors is essential for their use in integrated circuits. In addition to the mobility, the threshold voltage, Vth, is a key parameter to control for proper circuit operation. In this work, we demonstrate the controlled tuning of Vth of solution-processed, small-molecule, organic semiconductor transistors via molecular doping of the solution at multiple different doping levels.

We have investigated the contact-doping effect on high performance n-channel C60 organic field-effect transistors (OFETs) using the air-stable rhodocene dimer as an n-type dopant. The average charge mobility improved from a value of 0.48 cm2/(Vs) in a reference device to 1.65 cm2/(Vs) for contact-doped devices with a channel length of 25 μm. The operational stability of contact-doped OFETs under continuous stress bias was found similar to the reference devices.

We investigate trap-state passivation by addition of ultra-low amounts of n-dopants in organic field-effect transistors (OFET) made of as-received and purified fullerene C60. We find a strong dependence of the OFET threshold voltage (VT) on the density of traps present in the layer. In the case of the unpurified material, VT is reduced from 17.9 V to 4.7 V upon trap passivation by a dopant:C60 ratio of ∼10−3, while the Ion/off current ratio remains high. This suggests that ultra-low doping can be used to effectively compensate impurity and defect-related traps.

Solution-based n-doping of the polymer poly{[N,N′-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5′-(2,2′-bithiophene)} [P(NDI2OD-T2)] and the small molecule 6,13-bis(tri(isopropyl)silylethynyl)pentacene (TIPS-pentacene) is realized with the air-stable dimers of rhodocene, [RhCp2]2, and ruthenium(pentamethylcyclopentdienyl)(1,3,5-triethylbenzene), [Cp*Ru(TEB)]2. Fermi level shifts, measured by direct and inverse photoemission spectroscopy, and orders of magnitude increase in current density and film conductivity point to strong n-doping in both materials. The strong reducing power of these air-stable dopants is demonstrated through the n-doping of TIPS-pentacene, a material with low electron affinity (3.0 eV). Doping-induced reduction of the hopping transport activation energy indicates that the increase in film conductivity is due in part to the filling of deep gap states by carriers released by the dopants.

We demonstrate that holes from a p-doped N,N′-diphenyl-N,N′-bis(1-naphthyl)-1,1′-biphenyl-4,4′-diamine (α-NPD) layer transfer to an adjacent pentacene film. The spatial separation of carriers from dopants, or remote doping, is demonstrated with a combination of photoemission spectroscopy and current-voltage measurements for a p-doped α-NPD/pentacene heterojunction. Increased conductivity of the pentacene film is observed in both nongated temperature-dependent conductivity and gated thin-film transistor measurements.

A narrow band-gap alternating copolymer of perylene diimide and bis(dithienothiophene) (2) and a polythiophene derivative substituted by a tris(thienylenevinylene) conjugated side chain (4) are used as acceptor and donor, respectively, in all-polymer solar cells (SCs). The optimized device based on the blend of 4 and 2 in the ratio 3:1 (w/w) gives a short circuit current (Jsc) of 5.02 mA cm−2 and a power conversion efficiency of 1.48%, under simulated AM 1.5 illumination at 100 mW cm−2. These values are among the highest values reported for all-polymer SCs.

Electrical or chemical doping of molecular films is an efficient means of improving and controlling charge injection and carrier transport in organic devices. Recent work demonstrated that bis(cyclopentadienyl)cobalt(II) (cobaltocene, CoCp2) efficiently dopes a tris(thieno)hexaazatriphenylene (THAP) derivative, as shown by a 0.56eV shift of the Fermi level toward the empty states and an increase of current density by a factor of 103 over undoped THAP devices. In this work, a combination of x-ray photoemission spectroscopy and Rutherford backscattering is used to elucidate the details of dopant incorporation into bulk films. Cobaltocene is observed to codeposit into the THAP matrix in a controllable manner, with preferential adsorption of the dopant onto the surface of the host film. In the case of CoCp2-doped tris(8-hydroxy-quinolinato) aluminum (Alq3) films, negligible amounts of the dopant are found in the bulk matrix and on the film surface, resulting in minimal improvements in the electrical character...

The development of a high-performance photorefractive polymer composite operating at 1550 nm is reported. We show 40% internal diffraction efficiency with response time of 35 ms and a net gain of 20cm−1 in four-wave mixing and two-beam coupling experiments, respectively. This is more than an order of magnitude improvement in the diffraction efficiency and net two beam coupling gain and two orders of magnitude in the response time than the previously reported photorefractive polymer operating at this technologically important wavelength. The improvement in photorefractive characteristics is accomplished by an enhanced orientation of the nonlinear optical chromophore in the present composite.