Charge Carriers and Excited States in Supramolecular Materials

The field of organic electronics has been thriving for the last decades due to growing commercial interest. One of the advantages of using organic materials as semiconductors is the possibility to tune their optoelectronic properties by modifying the chemical structure and organization of the building blocks. In this thesis, the properties of...

Photoluminescence enhancement in thin films of PbSe nanocrystals

Remarkable photoluminescence enhancement (PLE) in submonolayer films of PbSe nanocrystals (NCs) upon continuous illumination was observed. The intensity increase from films on InP substrates was highest in vacuum, while for films on Si/SiO2 substrates the PLE was stronger in air. The magnitude of the PLE was found to depend on the excitation...

High-resolution luminescence spectroscopy study of down-conversion routes in NaGdF4:Nd3+ and NaGdF4:Tm3+ using synchrotron radiation

Terahertz Raman laser based on silicon doped with phosphorus

Raman-type stimulated emission at frequencies between 5.0 and 5.2?THz as well as between 6.1 and 6.4?THz has been realized in silicon crystals doped by phosphorus donors. The Raman laser operates at around 5?K under optical excitation by a pulsed, frequency-tunable infrared free electron laser. The frequencies of the observed laser emission are...

Mechanism of Persistent Luminescence in Eu2+ and Dy3+ Codoped Aluminate and Silicate Compounds

A mechanism of persistent luminescence that was proposed in 1996 for SrAl2O4:Eu2+;Dy3+ has been widely adopted to explain afterglow in many Eu2+ and Dy3+ codoped aluminates and silicates. The mechanism involves the thermally activated release of a hole from Eu2+ in its excited 5d state to the valence band which is subsequently trapped by Dy3+....

Excited-state spectroscopy on a nearly closed quantum dot via charge detection

We demonstrate a method for measuring the discrete energy spectrum of a quantum dot connected very weakly to a single lead. A train of voltage pulses applied to a metal gate induces tunneling of electrons between the quantum dot and a reservoir. The effective tunnel rate depends on the number and nature of the energy levels in the dot made...

Temperature dependent spectroscopic studies of the electron delocalization dynamics of excited Ce ions in the wide band gap insulator, Lu2SiO5

Electron delocalization processes of optically excited states of Ce3+ impurities in Lu2SiO5 were investigated by means of a temperature and spectrally resolved photoconductivity study. By monitoring separately the strength of the photocurrent resulting from excitation into each of the Ce3+?5d absorption bands, over a broad temperature region,...

Tuning of the excited state properties of phenylenevinylene oligomers: A time-dependent density functional theory study

This paper discusses a time-dependent density functional theory study of the effect of molecular structure on the excited state polarizability of conjugated molecules. A short phenylenevinylene oligomer containing three phenyl rings (PV2, distyryl benzene) is taken as a model system. Introduction of methyl substituents is shown to have only a...

Excited state polarizabilities of conjugated molecules calculated using time dependent density functional theory

In this paper, time-dependent density functional theory (TDDFT) calculations of excited state polarizabilities of conjugated molecules are presented. The increase in polarizability upon excitation was obtained by evaluating the dependence of the excitation energy on an applied static electric field. The excitation energy was found to vary...