Topic
Exciton
About: Exciton is a research topic. Over the lifetime, 31603 publications have been published within this topic receiving 810642 citations.
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TL;DR: In this paper, a simple theory of the magnetic field effects of triplet excitons is presented, and applied to the experimental field dependence results yields new information about the mechanisms of these interactions.
Abstract: The rates of many bimolecular reactions involving triplet excitons are magnetic field dependent at room temperature and for modest field strengths. The specific interactions discussed are the fusion of a pair of triplet excitons to yield either a single or triplet exciton, the interaction between a triplet exciton and a trapped triplet, the fission of a singlet exciton into a pair of triplets and the triplet exciton-free radical interaction. The magnetic field effects result from the influence of the field on the spin wavefunctions of the triplet exciton together with the existence of spin selection rules for the interactions. A simple theory of these effects is presented. Application of the theory to the experimental field dependence results yields new information about the mechanisms of these interactions.
157 citations
TL;DR: In this article, the temperature dependence of the intrinsic radiative recombination coefficient B in silicon was measured from 100 to 400 °K and a unique theory of the indirect radiative band-to-band and free exciton recombination was given.
Abstract: The temperature dependence of the intrinsic radiative recombination coefficient B in silicon was measured from 100 to 400 °K. In contrast to previous calculations, B decreases with temperature. For interpretation of the measurements, a unique theory of the indirect radiative band-to-band and free exciton recombination is given. The decrease of B with increasing T is due to the decrease to the exciton concentration and of the Coulomb-enhancement of the band-to-band recombination rate. The latter however is smaller than the exciton recombination part even at room temperature. The constants of the exciton and band-to-band recombination are determined.
157 citations
TL;DR: In this article, a theoretical model that describes the polariton dynamics in a semiconductor microcavity at large densities, for the case of nonresonant excitation, is presented.
Abstract: We present a theoretical model that allows us to describe the polariton dynamics in a semiconductor microcavity at large densities, for the case of nonresonant excitation. Exciton-polariton scattering from a thermalized exciton reservoir is identified as the main mechanism for relaxation into the lower polariton states. A maximum in the polariton distribution that shifts towards lower energies with increasing pump power or temperature is shown, in agreement with recent experiments. Above a critical pump power, macroscopic occupancies (5x10(4)) can be achieved in the lowest-energy polariton state. Our model predicts the possibility of Bose-Einstein condensation of polaritons, driven by exciton-polariton interaction, at densities well below the saturation density for CdTe microcavities.
157 citations
TL;DR: In this article, a charge transfer state was observed at the molecular interface between a conjugated polymer and a fullerene based electron acceptor, which can be photoexcited by tuning the excitation energy below the conjugate polymer bandgap.
Abstract: We report on the observation of a charge-transfer state forming at the molecular interface between a conjugated polymer and a fullerene based electron acceptor. Electron hole recombination in this state results in a luminescent transition at 840nm, energetically separated from the polymer emission. This transition can be directly photoexcited by tuning the excitation energy below the conjugated polymer bandgap, demonstrating that the charge-transfer state originates from a ground-state interaction. By electric field induced quenching of the photoluminescence, we determine a binding energy of 130meV for excitons in the charge-transfer state.
157 citations
TL;DR: An in-depth study of the TPA properties of CsPbBr3 QDs with mean size ranging from 4.6 to 11.4 nm is presented and it is found that TPA cross section is proportional to the linear one photon absorption.
Abstract: All-inorganic colloidal perovskite quantum dots (QDs) based on cesium, lead, and halide have recently emerged as promising light emitting materials. CsPbBr3 QDs have also been demonstrated as stable two-photon-pumped lasing medium. However, the reported two photon absorption (TPA) cross sections for these QDs differ by an order of magnitude. Here we present an in-depth study of the TPA properties of CsPbBr3 QDs with mean size ranging from 4.6 to 11.4 nm. By using femtosecond transient absorption (TA) spectroscopy we found that TPA cross section is proportional to the linear one photon absorption. The TPA cross section follows a power law dependence on QDs size with exponent 3.3 ± 0.2. The empirically obtained power-law dependence suggests that the TPA process through a virtual state populates exciton band states. The revealed power-law dependence and the understanding of TPA process are important for developing high performance nonlinear optical devices based on CsPbBr3 nanocrystals.
157 citations