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- Askat E Jailaubekov, Adam P Willard, +8 authors X-Y Zhu
- Nature materials
- 2013

Photocurrent generation in organic photovoltaics (OPVs) relies on the dissociation of excitons into free electrons and holes at donor/acceptor heterointerfaces. The low dielectric constant of organic semiconductors leads to strong Coulomb interactions between electron-hole pairs that should in principle oppose the generation of free charges. The exact… (More)

We carry out a comprehensive theoretical and experimental study of charge injection in poly͑3-hexylthiophene͒ ͑P3HT͒ to determine the most likely scenario for metal-insulator transition in this system. We calculate the optical-absorption frequencies corresponding to a polaron and a bipolaron lattice in P3HT. We also analyze the electronic excitations for… (More)

- Na Sai, Paul F Barbara, Kevin Leung
- Physical review letters
- 2011

We use first-principles computational methods to examine hole trapping in organic molecular crystals. We present a computational scheme based on the tuning of the fraction of exact exchange in hybrid density functional theory to eliminate the many-electron self-interaction error. With small organic molecules, we show that this scheme gives accurate… (More)

- Neil Bushong, Na Sai, Massimiliano Di Ventra
- Nano letters
- 2005

We show, using a tight-binding model and time-dependent density-functional theory, that a quasi-steady-state current can be established dynamically in a finite nanoscale junction without any inelastic effects. This is simply due to the geometrical constriction experienced by the electron wave packets as they propagate through the junction. We also show that… (More)

- Na Sai, Michael Zwolak, Giovanni Vignale, Massimiliano Di Ventra
- Physical review letters
- 2005

Using time-dependent current-density functional theory, we derive analytically the dynamical exchange-correlation correction to the dc conductance of nanoscale junctions. The correction pertains to the conductance calculated in the zero-frequency limit of time-dependent density functional theory within the adiabatic local-density approximation. In… (More)

We report studies of ferroelectricity in ultra-thin perovskite films with realistic electrodes. The results reveal stable ferroelectric states in thin films less than 10Å thick with polarization normal to the surface. Under short-circuit boundary conditions, the screening effect of realistic electrodes and the influence of real metal/oxide interfaces on… (More)

- Stanley S Chou, Na Sai, +6 authors C Jeffrey Brinker
- Nature communications
- 2015

Establishing processing-structure-property relationships for monolayer materials is crucial for a range of applications spanning optics, catalysis, electronics and energy. Presently, for molybdenum disulfide, a promising catalyst for artificial photosynthesis, considerable debate surrounds the structure/property relationships of its various allotropes. Here… (More)

- Kevin Leung, Ida M B Nielsen, Na Sai, Craig Medforth, John A Shelnutt
- The journal of physical chemistry. A
- 2010

We apply first principles computational techniques to analyze the two-electron, multistep, electrochemical reduction of CO(2) to CO in water using cobalt porphyrin as a catalyst. Density functional theory calculations with hybrid functionals and dielectric continuum solvation are used to determine the steps at which electrons are added. This information is… (More)

- Z Q Li, V Podzorov, +4 authors D N Basov
- Physical review letters
- 2007

We report on an infrared spectroscopy study of mobile holes in the accumulation layer of organic field-effect transistors based on rubrene single crystals. Our data indicate that both transport and infrared properties of these transistors at room temperature are governed by light quasiparticles in molecular orbital bands with the effective masses m*… (More)

- P J Michalski, Na Sai, E J Mele
- Physical review letters
- 2005

We develop and solve a continuum theory for the piezoelectric response of one-dimensional nanotubes and nanowires, and apply the theory to study electromechanical effects in boron-nitride nanotubes. We find that the polarization of a nanotube depends on its aspect ratio, and a dimensionless constant specifying the ratio of the strengths of the elastic and… (More)