A5025280692- Organic Light-Emitting Diodes Research
- Organic Electronics and Photovoltaics
- Luminescence and Fluorescent Materials
- X-ray Diffraction in Crystallography
- N-Heterocyclic Carbenes in Organic and Inorganic Chemistry
- Crystallization and Solubility Studies
- Conducting polymers and applications
- Catalytic Cross-Coupling Reactions
- Thin-Film Transistor Technologies
- CCD and CMOS Imaging Sensors
- Catalytic C–H Functionalization Methods
- Particle Accelerators and Free-Electron Lasers
- Cyclopropane Reaction Mechanisms
- Laser-Matter Interactions and Applications
- Laser-Plasma Interactions and Diagnostics
- Perovskite Materials and Applications
- Quantum Information and Cryptography
- Advanced Optical Imaging Technologies
- Advanced Materials and Mechanics
- Crystallography and molecular interactions
- Analytical Chemistry and Sensors
- Advanced X-ray Imaging Techniques
- Molecular Junctions and Nanostructures
- Lanthanide and Transition Metal Complexes
- Organoboron and organosilicon chemistry
University of Michigan
2015-2021
Ann Arbor Center for Independent Living
2019
Brigham Young University
2016
Abstract Metal-free organic phosphorescent materials are attractive alternatives to the predominantly used organometallic phosphors but generally dimmer and relatively rare, as, without heavy-metal atoms, spin–orbit coupling is less efficient phosphorescence usually cannot compete with radiationless relaxation processes. Here we present a general design rule method effectively reduce transitions hence greatly enhance efficiency of metal-free in variety amorphous polymer matrices, based on...
A series of six luminescent two-coordinate Cu(I) complexes were investigated bearing nonconventional N-heterocyclic carbene ligands, monoamido-aminocarbene (MAC*) and diamidocarbene (DAC*), along with carbazolyl (Cz) as well mono- dicyano-substituted Cz derivatives. The emission color can be systematically varied over 270 nm, from violet to red, through proper choice the acceptor (carbene) donor (carbazolyl) groups. compounds exhibit photoluminescent quantum efficiencies up 100% in fluid...
Abstract Since their introduction over 15 years ago, the operational lifetime of blue phosphorescent organic light-emitting diodes (PHOLEDs) has remained insufficient for practical use in displays and lighting. Their short results from annihilation between high-energy excited states, producing energetically hot states (>6.0 eV) that lead to molecular dissociation. Here we introduce a strategy avoid dissociative reactions by including state manager within device emission layer. Hot...
We demonstrate efficient light extraction from the active region of bottom-emitting organic emitting devices (OLEDs) using a high refractive index, nondiffractive hemispherical microlens array located between transparent anode and embedded in low index glass substrate (n = 1.5). The subelectrode (SEMLA) results maximum external quantum efficiency 70 ± 4% for green phosphorescent OLEDs (PHOLEDs). Furthermore, wavelength- viewing-angle-independent structure white PHOLED efficiencies 50 3%....
Abstract The photophysical and electrochemical properties of N‐heterocyclic carbene complexes Iridium (III) (Ir(C ^ C:) 3 , where C C: = N‐phenyl,N‐methyl‐pyrazinoimidazol‐2‐yl (pmpz), N,N‐di‐p‐tolyl‐pyrazinoimidazol‐2‐yl (tpz)) are reported. Facial meridional isomers Ir(pmpz) prepared, but only the facial isomer can be isolated for Ir(tpz) . fac ‐Ir(pmpz) ‐Ir(tpz) have emission maxima at 465 nm in polystyrene, whereas maximum mer is redshifted to 495 nm. energies photoluminescent quantum...
We demonstrate high-efficiency light extraction for top-emitting organic light-emitting devices (OLEDs) comprising a transparent conductive oxide on the surface of nondiffractive, reflecting metal-coated scattering grid located beneath active region. The scatters trapped in waveguide modes without changing device electrical properties or causing significant plasmonic losses. This results an increase external quantum efficiency green phosphorescent from 20 ± 1% to 30 2%, structures and with...
A class of wide bandgap host materials is introduced as an alternative to carbazole-based hosts enhance the efficiency and transport properties organic light emitting diodes (OLEDs).
It has long been a challenge to develop highly efficient outcoupling method for organic light-emitting diodes that is independent of wavelength and viewing angle, as well being nonintrusive into the device structure. Here, we demonstrate transparent, top emitting structure integrated with high index refraction waveguide layer rough, dielectric diffuse reflector eliminates plasmonic, waveguide, substrate modes without introducing viewing-angle dependence. The simple increases external quantum...
High efficiency solid state lighting devices have the potential to significantly reduce energy usage while also offering good color rendering and longer lifetimes than conventional sources. While organic light emitting diodes are promising candidates for this application, their operational lifetime is limited by blue phosphorescent chromophore. We demonstrate stacked white (SWOLEDs) with (as determined from time it takes lose 30% of initial luminance 1000 cd/m2) up 80000 h. The correlated...
Thin red "sensing layers" are used to measure exciton confinement and charge balance in blue phosphorescent light emitting diodes. The device stability efficiency improved by preventing triplet leakage from the emission zone. results explained using a quantitative model for transport. As service our authors readers, this journal provides supporting information supplied authors. Such materials peer reviewed may be re-organized online delivery, but not copy-edited or typeset. Technical support...
Significance We demonstrate a general method to transform planar electronic and optoelectronic devices fabricated by conventional photolithography into strain-free but topologically different geometry. The is used hemispherical, retina-like imagers whose pixel spacings are unaffected the topological transformation. Our approach overcomes critical limitation of distortion encountered in transforming circuit nondevelopable, 3D shape. process opens up additional possibilities for making variety...
For 15 years, the rapid degradation of luminance over time has rendered blue phosphorescent light emitting diodes (PHOLEDs) too short-lived for many practical applications. To date, studies have concentrated on materials, yet not other parts these devices. The authors develop a method to measure charge and exciton leakage directly time, find that effects are $n\phantom{\rule{0}{0ex}}o\phantom{\rule{0}{0ex}}t$ responsible PHOLED degradation---an important revelation shifts our attention...
We present calibrated measurements of single-photon Thomson scattering from free electrons driven by a laser with intensity 1018 W/cm2. The demonstrate that individual radiate the strength point emitters, even when their wave packets spread to scale driving-laser wavelength. result agrees predictions quantum electrodynamics.
Charge coupled devices (CCDs), often used for scientific imaging and photography, conventionally comprise an active inorganic semiconductor such as silicon. Organic semiconductors, however, are typically unsuited application due to their low charge mobilities short carrier lifetimes. Here, we demonstrate a CCD using organic materials. It is based on unique channel geometry with relatively high electron very long lifetimes demonstrated by Burlingame et al. (Nature 2018, 554, 77). Repulsive...