A5045853606- Organic Electronics and Photovoltaics
- Conducting polymers and applications
- X-ray Diffraction in Crystallography
- Crystallization and Solubility Studies
- Molecular Junctions and Nanostructures
- Organic Light-Emitting Diodes Research
- Photochemistry and Electron Transfer Studies
- Organic and Molecular Conductors Research
- Perovskite Materials and Applications
- Luminescence and Fluorescent Materials
- Synthesis and Properties of Aromatic Compounds
- Advanced Chemical Physics Studies
- Fullerene Chemistry and Applications
- Crystallography and molecular interactions
- Porphyrin and Phthalocyanine Chemistry
- Spectroscopy and Quantum Chemical Studies
- Nonlinear Optical Materials Research
- Magnetism in coordination complexes
- Graphene research and applications
- Thin-Film Transistor Technologies
- Synthesis and properties of polymers
- Solid-state spectroscopy and crystallography
- Carbon Nanotubes in Composites
- Semiconductor materials and interfaces
- Electrochemical Analysis and Applications
University of Arizona
2006-2025
Georgia Institute of Technology
2012-2021
AID Atlanta
2016-2020
King Abdulaziz University
2017
King Abdullah University of Science and Technology
2017
University of Mons
2004-2010
Institut des Sciences Moléculaires
2010
Université de Bordeaux
2010
University of Cambridge
2009-2010
University of Washington
2010
Our objective in this Account is 3-fold. First, we provide an overview of the optical and electronic processes that take place a solid-state organic solar cell, which define as cell semiconducting materials between electrodes are organic, be them polymers, oligomers, or small molecules; discussion also meant to set conceptual framework many contributions Special Issue on Photovoltaics can viewed. We successively turn our attention (i) absorption exciton formation, (ii) migration...
The rates for up-conversion intersystem crossing (UISC) from the T1 state to S1 are calculated a series of organic emitters with an emphasis on thermally activated delayed fluorescence (TADF) materials. Both spin-orbit coupling and energy difference between states (ΔEST) evaluated, at density functional theory (DFT) time-dependent DFT levels. UISC ΔEST values found be in good agreement available experimental data. Our results underline that small sizable matrix elements have simultaneously...
Theoretical investigations of charge transport in organic materials are generally based on the "energy splitting dimer" method and routinely assume that parameters (site energies transfer integrals) determined from monomer dimer calculations can be reliably used to describe extended systems. Here, we demonstrate this transferability fail even molecular crystals with weak van der Waals intermolecular interactions, due substantial (but often ignored) impact polarization effects, particularly...
Abstract A major challenge for organic solar cell (OSC) research is how to minimize the tradeoff between voltage loss and charge generation. In early 2019, we reported a non-fullerene acceptor (named Y6) that can simultaneously achieve high external quantum efficiency low OSC. Here, use combination of experimental theoretical modeling reveal structure-property-performance relationships this state-of-the-art OSC system. We find distinctive π–π molecular packing Y6 not only exists in single...
We describe at the quantum-chemical level main parameters that control charge transport molecular scale in discotic liquid crystals. The focus is on stacks made of triphenylene, hexaazatriphenylene, hexaazatrinaphthylene, and hexabenzocoronene molecules derivatives thereof. It found a subtle interplay between chemical structure their relative positions within determines properties; features required to promote high mobilities materials are established basis calculated structure−property...
The reorganization energy in pentacene is reported on the basis of a joint experimental and theoretical study ionization using high-resolution gas-phase photoelectron spectroscopy, semiempirical intermediate neglect differential overlap calculations, first-principles correlated quantum-mechanical calculations at MP2 density functional theory levels. upon positive determined both experimentally theoretically to be remarkably low. This one key element that allows rationalize extremely high...
The hole-vibrational coupling is reported for anthracene, tetracene, and pentacene on the basis of a joint experimental theoretical study ionization spectra using high-resolution gas-phase photoelectron spectroscopy first-principles correlated quantum-mechanical calculations. found to be significantly smaller than electron-vibrational in case these oligomers; however, both quantities are predicted converge same value when increasing chain length.
A comprehensive study of the photophysical properties a series monoaza[5]helicenes is presented on basis joint optical spectroscopy and quantum chemistry investigations. The molecules have been characterized by absorption CW/time-resolved luminescence measurements. All quantities related to spin−orbit-coupling processes, such as intersystem crossing rates radiative phosphorescence lifetimes, were found depend strongly nitrogen position within carbon backbone. Density functional theory...
Abstract The anisotropy inherent to many planar organic molecules leads a high sensitivity of various fundamental processes the orientation within films and at heterojunctions. Such include absorption, charge exciton transport, energy levels, transfer, all which are critical solar cell operation. Here,an in‐depth study bilayer cells consisting donor/acceptor interface between zinc phthalocyanine (ZnPc) fullerene (C 60 ) is conducted devices with typically deposited standing up (edge‐on)...
The exciton-dissociation and charge-recombination processes in organic solar cells based on pentacene/C(60) heterojunctions are investigated by means of quantum-mechanical calculations. electronic couplings the rates exciton dissociation charge recombination have been evaluated for several geometrical configurations complex, which relevant to bilayer bulk heterojunctions. results suggest that, irrespective actual pentacene-fullerene orientation, both pentacene-based C(60)-based excitons able...
Record power conversion efficiencies (PCEs) of perovskite solar cells (PSCs) have been obtained with the organic hole transporter 2,2',7,7'-tetrakis(N,N-di-p-methoxyphenyl-amine)9,9'-spirobifluorene (spiro-OMeTAD). Conventional doping spiro-OMeTAD hygroscopic lithium salts and volatile 4-tert-butylpyridine is a time-consuming process also leads to poor device stability. We developed new strategy for that avoids post-oxidation by using stable radicals as dopant ionic modulator (referred...
Tail states in organic semiconductors have a significant influence on device performances by acting as traps charge transport. We present study of the controlled passivation acceptor tail fullerene ${\mathrm{C}}_{60}$ addition electrons introduced molecular $n$ doping. Using ultralow doping, we are able to successively fill with charges and examine changes conductivity, activation energy, mobility, Fermi-level position. Passivation leads an increase electron mobility more than 3 orders...
We have used density functional theory calculations and mixed quantum/classical dynamics simulations to study the electronic structure charge-transport properties of three representative mixed-stack charge-transfer crystals, DBTTF-TCNQ, DMQtT-F(4)TCNQ, STB-F(4)TCNQ. The compounds are characterized by very small effective masses modest electron-phonon couplings for both holes electrons. hole electron transport characteristics found be similar along stacking directions; example, in...
A long standing question in organic electronics concerns the effects of molecular orientation at donor/acceptor heterojunctions. Given a well-controlled bilayer system, we uncover genuine on charge generation and recombination. These are studied through point view photovoltaics-however, results have important implications operation all optoelectronic devices with interfaces, such as light emitting diodes photodetectors. Our findings can be summarized by two points. First, donor molecules...
Enhancing the luminescence property without sacrificing charge collection is one key to high-performance organic solar cells (OSCs), while limited by severe non-radiative recombination. Here, we demonstrate efficient OSCs with high via design and synthesis of an asymmetric non-fullerene acceptor, BO-5Cl. Blending BO-5Cl PM6 donor leads a record-high electroluminescence external quantum efficiency 0.1%, which results in low voltage loss 0.178 eV power conversion (PCE) over 15%. Importantly,...
Abstract The charge-transfer electronic states appearing at the donor-acceptor interfaces in organic solar cells mediate exciton dissociation, charge generation, and recombination. To date, characterization of their nature has been carried out on basis models that only involve state ground state. Here, we demonstrate it is essential to go beyond such a two-state model consider explicitly as well vibrational couplings with local absorbing donor and/or acceptor. We have thus developed...
Organosulfur polymers, such as those derived from elemental sulfur, are an important new class of macromolecules that have recently emerged via the inverse vulcanization process. Since launching this field in 2013, development monomers and organopolysulfide materials based on process is now active area polymer chemistry. While numerous advances been made over last decade concerning polymerization process, insights into mechanism structural characterization high-sulfur-content copolymers...
Abstract Donor‐acceptor (D–A • ) type luminescent organic radicals have received widespread attention as efficient doublet emitters. However, their generally low photoluminescence quantum efficiency (PLQE) and limited photostability restrict various applications. Since unraveling the relationship between structure properties of D–A remains a challenge, here, series tri(2,4,6‐trichlorophenyl)methyl (TTM) radical derivatives, which differ by location ring fusion sites nature heteroatoms, is...
The charge-transport parameters of the perfluoropentacene and perfluorotetracene crystals are studied with a joint experimental theoretical approach that combines gas-phase ultraviolet photoelectron spectroscopy density functional theory. To gain better understanding role perfluorination, results for compared to those their parent oligoacenes, is, pentacene tetracene. Perfluorination is calculated increase ionization potentials electron affinities by approximately 1 eV, which expected reduce...