Defects play a significant role in tailoring the optical properties of two-dimensional materials. Optical signatures of defect-bound excitons are important tools to probe defective regions and thus interrogate the optical quality of as-grown semiconducting monolayer materials. We have performed a systematic study of defect-bound excitons using photoluminescence (PL) spectroscopy combined with a...

2014 We report the spectral and time characteristics of the fluorescence of CsMnF3. The weak intrinsic fluorescence in nominally pure samples is analysed with time resolved techniques showing the energy transfer processes from exciton to fluorescing traps. By applying either a uniaxial stress along the Mn2-Mn1 direction or a high magnetic field in the basal plane we are able to monitor the effi...

Exciton binding energies of heavyand light-hole excitons affected by charge-carrier screening in GaAs-Al„Ga& As quantum wells are calculated by the variational-perturbation method. The exciton binding energies are found to decrease rapidly when the screening length is less than 30az (effective exciton Bohr radius). This screening length corresponds to a carrier density of 7.0X 10"/cm at T=10 K....

We introduce a computationally efficient approach to calculating characteristics of excitons in quantum wells. In this approach we derive a system of self-consistent equations describing the motion of an electron–hole pair. The motion in the growth direction of the quantum well in this approach is separated from the in-plane motion, but each of them occurs in modified potentials found self-cons...

Free exciton (FX) and bound exciton (BX) in Al0.5Ga0.5N/Al0.35Ga0.65N multiple quantum wells (MQWs) with different Si-doping levels in the well layers are investigated by photoluminescence (PL) spectra. Low temperature (10 K) PL spectra identify a large binding energy of 87.4 meV for the BX in undoped sample, and 63.6 meV for the BX in Si-doped (2 × 10(18 ) cm(-3)) sample. They are attributed t...

Graphene nanoribbons display extraordinary optical properties due to one-dimensional quantum-confinement, such as width-dependent bandgap and strong electron-hole interactions, responsible for the formation of excitons with extremely high binding energies. Here we use femtosecond transient absorption spectroscopy to explore the ultrafast optical properties of ultranarrow, structurally well-defi...

Recently, inorganic and hybrid light absorbers such as quantum dots and organometal halide perovskites have been studied and applied in fabricating thin-film photovoltaic devices because of their low-cost and potential for high efficiency. Further boosting the performance of solution processed thin-film solar cells without detrimentally increasing the complexity of the device architecture is cr...

We investigate the electron-phonon coupling in CH3NH3PbX3 lead halide perovskites through observation of Landau levels and high-order excitons at weak magnetic fields, where cyclotron energy is significantly smaller than longitudinal optical phonon energy. The reduced masses carriers exciton binding energies obtained from these data are clearly influenced by polaron formation. analyze field-dep...

Highly luminescent isolated polydiacetylene (PDA) chains in a new diacetylene crystal are studied. The diacetylene crystal structure and theoretical calculations suggest that the chains are not planar and more strongly twisted than any known PDA. Yet the chains behave as quasi perfect quantum wires, showing that this behaviour is generic among PDA, provided crystal order is high enough. The exc...

Graphene oxide has recently been considered to be a potential replacement for cadmium-based quantum dots due to its expected high fluorescence. Although previously reported, the origin of the luminescence in graphene oxide is still controversial. Here, we report the presence of core/valence excitons in graphene-based materials, a basic ingredient for optical devices, induced by quantum confinem...