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: It is demonstrated that the driving force for exciton dissociation at the fullerene-fullerene heterointerface is optimized for diameters <1.0 nm, which will guide the development of next-generation high-performance carbon nanotube-based solar cells and photosensitive devices.
Abstract: We have employed thin films of highly purified semiconducting carbon nanotubes as near-infrared optical absorbers in heterojunction photovoltaic and photodetector devices with the electron acceptor C60. In comparison with previous implementations of more electrically heterogeneous carbon nanotube/C60 devices, we have realized a 10× gain in zero-bias quantum efficiency (QE) and even more substantial gains in power conversion efficiency (ηp). The semiconducting nanotube/C60 heterojunctions are highly rectifying with a peak external QE, internal QE, and ηp of 12.9 ± 1.3, 91 ± 22, and 0.6%, respectively, in the near-infrared. We show that the device efficiency is determined by the effective length scale for exciton migration in the nanotube films, confirm the high internal QE via photoluminescence quenching, and demonstrate that the driving force for exciton dissociation at the fullerene-fullerene heterointerface is optimized for diameters <1.0 nm. These results will guide the development of next-generation h...
214 citations
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TL;DR: High electron and hole mobilities as well as balanced charge carrier injection lead to improved exciton generation in these gate-controlled devices and the effect of charge-induced absorption is substantially reduced in high-quality single crystals compared with amorphous organic materials.
Abstract: We report on electrically driven amplified spontaneous emission and lasing in tetracene single crystals using field-effect electrodes for efficient electron and hole injection. For laser action, feedback is provided by reflections at the cleaved edges of the crystal resulting in a Fabry-Perot resonator. Increasing the injected current density above a certain threshold value results in the decreasing of the spectral width of the emission from 120 millielectron volts to less than 1 millielectron volt because of gain narrowing and eventually laser action. High electron and hole mobilities as well as balanced charge carrier injection lead to improved exciton generation in these gate-controlled devices. Moreover, the effect of charge-induced absorption is substantially reduced in high-quality single crystals compared with amorphous organic materials.
214 citations
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TL;DR: The present result indicates the single-crystal organic LET is a promising device structure that is free from various kinds of nonradiative losses such as exciton dissociation near electrodes and exciton annihilations.
Abstract: We measured the external electroluminescence quantum efficiency (eta(ext)) in light-emitting field-effect transistors (LETs) made of organic single crystals and found that, in the ambipolar transport region, eta(ext) is not degraded up to several hundreds A/cm(2) current-density range, which is 2 orders of magnitude larger than that achieved in conventional organic light-emitting diodes. The present result indicates the single-crystal organic LET is a promising device structure that is free from various kinds of nonradiative losses such as exciton dissociation near electrodes and exciton annihilations.
214 citations
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TL;DR: In this article, a high efficiency organic electrophosphorescent device comprised of a 4,4,4′-tris(3-methylphenylphenylamino)triphenylamine (m-MTDATA) hole transport layer and a 4.4′,N,N′-dicarbazole-biphenyl (CBP) host doped with the metallorganic phosphor, factris (2-phenylpyridine)iridium (Ir(ppy)3) as the green light-emitting layer.
214 citations
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TL;DR: In this article, a relativistic Bethe-Salpeter Equation calculation (GW-BSE) was used to directly calculate excitonic properties from first-principles.
Abstract: 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 relativistic Bethe-Salpeter Equation calculations (GW-BSE). This method is capable to directly calculate excitonic properties from first-principles. At low temperatures it predicts exciton binding energies in agreement with the reported ‘large’ values. For MAPbI3, phonon modes present in this frequency range have a negligible contribution to the ionic screening. By calculating the polarization in time from finite temperature molecular dynamics, we show that at room temperature this does not change. We therefore exclude ionic screening as an explanation for the experimentally observed reduction of the exciton binding energy at room temperature and argue in favor of the formation of polarons.
213 citations