Single-walled carbon nanotubes (SWCNTs) are potentially strong optical absorbers with tunable absorption bands depending on their chiral indices (n, m). Their application for solar energy conversion is difficult because of the large binding energy (>100 meV) of electron-hole pairs, known as excitons, produced by optical absorption. Recent development of photovoltaic devices based on SWCNTs as l...

Solar cells based on organometal halide perovskites have seen rapidly increasing efficiencies, now exceeding 15%. Despite this progress, there is still limited knowledge on the fundamental photophysics. Here we use microwave photoconductance and photoluminescence measurements to investigate the temperature dependence of the carrier generation, mobility, and recombination in (CH3NH3)PbI3. At tem...

Because of their superior optical, and electrical properties, lead halide perovskites have emerged as potential materials for light-emitting-diodes. However, some obstacles yet to be overcome practical applications including low exciton binding energy, the difficulty fabricating uniform perovskite films,, instability heat, light, moisture. In this review, we focus on strategies improve lifetime...

We observe localization of excitons in semiconducting single-walled carbon nanotubes at room temperature using high-resolution near-field photoluminescence (PL) microscopy. Localization is the result of spatially confined exciton energy minima with depths of more than 15 meV connected to lateral energy gradients exceeding 2 meV/nm as evidenced by energy-resolved PL imaging. Simulations of excit...

The experimental data on triplet exciton transport in isotopically mixed crystals of naphthalene/ perdeuteronaphthalene (paper I) are contrasted with singlet exciton transport in the same samples (20%-100%) and analyzed in terms of incoherent hopping models. The master equation approach is emphasized and extended. We modify the conventional continuum master equations via a physically plausible ...

We have calculated the nonlinear response function of a DNA duplex helix including the contributions from the exciton population and coherence transfers by developing an appropriate exciton theory as well as by utilizing a projector operator technique. As a representative example of DNA double helices, the B-form (dA)10-(dT)10 is considered in detail. The Green functions of the exciton populati...

Many-body levels of optically excited and multiply charged InAs nanocrystals are studied with the semiempirical tight-binding model. Single-particle levels of unstrained spherical InAs nanocrystals are described by the spds* nearest-neighbor tight-binding model including spin-orbit coupling. For optically excited InAs nanocrystals, first-order corrections of electron-hole Coulomb and exchange i...

The variational results for the free energy of an interacting exciton phonon system are used to derive expressions for the scattering rate and diffusion constant of an exciton in such a system. These expressions are applicable to both wide and narrow band cases, and includes the possibility of an abrupt transition from wide band (free) exciton to narrow band (localized) exciton. Some comments a...

Density functional theory calculation was conducted to determine the optoelectronic properties of bismuth titanate sillenite (Bi12TiO20) and perovskite-like (Bi4Ti3O12) structures. The lattice parameters were experimentally obtained from Rietveld analysis. The density functional perturbation theory approach was used with the standard Perdew-Burke-Ernzerhof functional and screened Coulomb hybrid...