32 research outputs found
Exciton/Charge-transfer Electronic Couplings in Organic Semiconductors
Charge transfer (CT) states and excitons are important in energy conversion processes that occur in organic light emitting devices (OLEDS) and organic solar cells. An ab initio density functional theory (DFT) method for obtaining CTâexciton electronic couplings between CT states and excitons is presented. This method is applied to two organic heterodimers to obtain their CTâexciton coupling and adiabatic energy surfaces near their CTâexciton diabatic surface crossings. The results show that the new method provides a new window into the role of CT states in excitonâexciton transitions within organic semiconductors.United States. Dept. of Energy (DEFG02- 07ER46474)David & Lucile Packard Foundation (Fellowship
Newly Discovered Sauropod Dinosaur Tracks with Skin and Foot-Pad Impressions from the Upper Jurassic Morrison Formation, Bighorn Basin, Wyoming, U.S.A
Detailed analysis of charge transport in amorphous organic thin layer by multiscale simulation without any adjustable parameters
Influence of Chemical Structure on the Charge Transfer State Spectrum of a Polymer:Fullerene Complex
Concentration dependent energy levels shifts in donor-acceptor mixtures due to intermolecular electrostatic interaction
Molecular Insight Into the Energy Levels at the Organic Donor/Acceptor Interface: A QM/MM Study
We present an investigation of the band levels and charge transfer (CT) states at the interface between two organic semiconductors, metal-free phthalocyanine (H2Pc) and 3,4,9,10-perylenetetracarboxylic bisbenzimidazole (PTCBI), using a combined quantum mechanics/molecular mechanics (QM/MM) technique. Near the organicâorganic interface, significant changes from the bulk, as large as 0.2 eV, are found in the excited state energies, ionization potentials, and electron affinities, due to differences in molecular packing and polarizabilities of the two molecules. The changes in the ionization potential and electron affinity cause the CT states at the interface to be on average higher in energy than fully separated charges in the bulk materials despite having a typical local binding energy of 0.15 eV. Furthermore, we find that thermal fluctuations can induce variations of up to 0.1 eV in the CT binding energy. These results suggest that it is possible for bound interfacial CT states to dissociate in a barrierless fashion without involving âhotâ CT states. This observation has direct relevance to the design of more efficient organic photovoltaics.United States. Dept. of Energy (DE-FG02- 07ER46474)Alfred P. Sloan FoundationDavid & Lucile Packard Foundatio