The two-state molecular orbital model of the one-dimensional phenyl-based semiconductors is applied to poly(para-phenylene vinylene). The energies of the low-lying excited states are calculated using the density matrix renormalization group method. Calculations of both the exciton size and the charge gap show that there are both 1B− u and 1 A + g excitonic levels below the band threshold. The e...

Excitonic solar cells, within which bound electron-hole pairs have a central role in energy harvesting, have represented a hot field of research over the last two decades due to the compelling prospect of low-cost solar energy. However, in such cells, exciton dissociation and charge collection occur with significant losses in energy, essentially due to poor charge screening. Organic-inorganic p...

The development of high efficiency perovskite solar cells has sparked a multitude of measurements on the optical properties of these materials. For the most studied methylammonium(MA)PbI3 perovskite, a large range (6-55 meV) of exciton binding energies has been reported by various experiments. The existence of excitons at room temperature is unclear. For the MAPbX3 perovskites we report on rela...

The electronic structure and size-scaling of optoelectronic properties in cycloparaphenylene carbon nanorings are investigated using time-dependent density functional theory (TDDFT). The TDDFT calculations on these molecular nanostructures indicate that the lowest excitation energy surprisingly becomes larger as the carbon nanoring size is increased, in contradiction with typical quantum confin...

The exciton transition and binding energies have been investigated in near-surface InGaAs/GaAs quantum wells theoretically and experimentally ~by photoluminescence and photoluminescence excitation spectroscopy at 4.2 K!. The contribution induced by vacuum has been analyzed for the ground and excited exciton states in perpendicular magnetic fields up to 14 T. The vacuum potential barrier has bee...

Low-dimensional materials differ from their bulk counterparts in many respects. In particular, the screening of the Coulomb interaction is strongly reduced, which can have important consequences such as the significant increase of exciton binding energies. In bulk materials the binding energy is used as an indicator in optical spectra to distinguish different kinds of excitons, but this is not ...

A PTZ-based D–A COF with low exciton binding energy and high charge separation efficiency exhibited an enhanced photocatalytic performance in oxidative amine coupling cyclization of thioamide reactions.

We present a theoretical investigation of electron-hole and exciton energy spectra as well as oscillator strengths of optical transitions in colloidal CdS quantum dots ~QD’s! with spherical and tetrahedral shape. The Coulomb potential energy of the electron-hole system is treated taking into account the dielectric mismatch at the QD boundaries. Calculation of electron-hole energy spectrum and C...