Morphology Effectively Controls Singlet-Triplet Exciton Relaxation and Charge Transport in Organic Semiconductors

有机分子中激子的光发射轨道层析成像

Photoemission orbital tomography for excitons in organic molecules

本研究将光发射轨道层析成像（POT）方法拓展至有机分子激子研究，兼顾激子波函数纠缠特性与光发射能量守恒，分类了通用激子结构并给出自然跃迁轨道解释，通过含时密度泛函理论模拟泵浦-探测实验验证结论。

Comment on On the Yield of Singlet Excitons in Organic Light-Emitting Devices: a Double Modulation Photoluminescence-Detected Magnetic Resonance Study

In a recent Letter Lee et al. studied the spin 1/2 photoluminescence-detected magnetic resonance (PLDMR) of a soluble derivative of poly-phenylene vinylene [MEH-PPV] and argued that it originates from the interaction of triplet excitons with polarons. We show that in MEH-PPV as well as in other conjugated polymers the spin 1/2 PLDMR does not depend on the triplet exciton density and thus cannot be associated with triplet excitons.

Spin-Triplet Excitons in the $S=1/2$ Gapped Antiferromagnet BaCuSi$_2$O$_6$: Electron Paramagnetic Resonance Studies

BaCuSi$_2$O$_6$, a $S=1/2$ quantum antiferromagnet with a double-layer structure of Cu$^{2+}$ ions in a distorted planar-rectangular coordination and with a dimerized spin singlet ground state, is studied by means of the electron paramagnetic resonance technique. It is argued that multiple absorptions observed at low temperatures are intimately related to a thermally-activated spin-triplet exciton superstructure. Analysis of the angular dependence of exciton modes in BaCuSi$_2$O$_6$ allows us to accurately estimate anisotropy parameters. In addition, the temperature dependence of EPR intensity…

Diffusion of triplet excitons in an operational Organic Light Emitting Diode

Measurements of the diffusion length L for triplet excitons in small molecular-weight organic semiconductors are commonly carried out using a technique in which a phosphorescent-doped probe layer is set in the vicinity of a supposed exciton generation zone. However, analyses commonly used to retrieve $L$ ignore microcavity effects that may induce a strong modulation of the emitted light as the position of the exciton probe is shifted. The present paper investigates in detail how this technique may be improved to obtain more accurate results for L. The example of 4,4'-bis(carbazol-9-yl)1,1'-bip…

Inelastic X-Ray Scattering Study of Exciton Properties in an Organic Molecular crystal

Excitons in a complex organic molecular crystal were studied by inelastic x-ray scattering (IXS) for the first time. The dynamic dielectric response function is measured over a large momentum transfer region, from which an exciton dispersion of 130 meV is observed. Semiempirical quantum chemical calculations reproduce well the momentum dependence of the measured dynamic dielectric responses, and thus unambiguously indicate that the lowest Frenkel exciton is confined within a fraction of the complex molecule. Our results demonstrate that IXS is a powerful tool for studying excitons in complex o…

Non-radiative exciton energy transfer in hybrid organic-inorganic heterostructures

Non-radiative optical energy transfer from a GaAs quantum well to a thin overlayer of an infrared organic semiconductor dye is unambiguously demonstrated. The dynamics of exciton transfer are studied in the time-domain using pump-probe spectroscopy at the donor site and fluorescence spectroscopy at the acceptor site. The effect is observed as simultaneous increase of the population decay rate at the donor and of the rise time of optical emission at the acceptor sites. The hybrid configuration under investigation provides an alternative non-radiative, non-contact pumping route to electrical car…