Photonics NCs

A colloidal synthesis of nanocrystals doesn't allow to

• NPs with approximately the same size or narrow distribution of sizes

• NPs with the same shape and topology of their surface

• NPs with the same chemical composition and lattice structure

• Obtaine a thin NC film on substrates

The efficient band gap energy of NCs ... due to the size of a quantum dot decreases

• Increases

• Decreases

• Does not change

Quantum dots of the first type are QDs characterized with

• A large-gap semiconductor is grown onto a narrow-gap semiconductor core (оболочка из полупроводника с большой шириной запрещенной зоны наращивается на ядро из полупроводника с меньшей шириной запрещенной зоны)

• A narrow-gap semiconductor is grown onto a large-gap semiconductor core (оболочка из полупроводника с меньшей шириной запрещенной зоны наращивается на ядро из полупроводника с большей шириной запрещенной зоны)

• The energy levels of an electron and a hole in the shell are located lower than in the nucleus; in this case, the band gap of the shell is approximately the same as that of the core (энергетические уровни электрона и дырки в оболочке располагаются ниже, чем в ядре; при этом ширина запрещенной зоны оболочки примерно такая же, как у ядра)

• The energy levels of an electron and a hole in the shell are located higher than in the nucleus; in this case, the band gap of the shell is approximately the same as that of the core (энергетические уровни электрона и дырки в оболочке располагаются выше, чем в ядре; при этом ширина запрещенной зоны оболочки примерно такая же, как у ядра)

Which process has the highest rate?

• Phosphorescence

• Fluorescence

• Intercombination conversion

• Vibrational relaxation

Photon radiation occurs only from the lowest excited state S1 or T1.

• Levshin's rule

• Stokes-Lommel rule

• Kasha's rule

• Vavilov's law

The emission spectrum of molecule doesn’t depend on the exciting light frequency.

• Levshin's rule

• Stokes-Lommel rule

• Kasha's rule

• Vavilov's law

What type of delayed fluorescence does not exist?

• E-type

• N-type

• P-type

The quantum yield of luminescence is a ratio of...

• the number of absorbed photons to the number of emitted photons

• the number of emitted photons to the number of absorbed photons

• the number of emitted photons to the number of incident photons

In nanoplatelets, the charge confinement occurs in ...

• one direction

• two directions

• three directions

A decrease in the size of a quantum dot ...... its luminescene band position.

• leads to a shift to shorter wavelengths

• leads to a shift to longer wavelengths

• doesn't change