Why is the thermalization of excited electrons in semiconductor nanoparticles so rapid? Studies on CdSe nanoparticles

Plasmonic Optical Properties and Applications of Metal Nanostructures

“…Another possible explanation for the difference is surface and/or solvent environment, which was found to affect electronic relaxation of Au NPs. [174][175][176] It is generally agreed that the electronphonon coupling constant is the same for Au NPs as for bulk, at least for particles down to 2 nm in diameter. [100,173,177] When the particle size is smaller than 1 nm, the electronic relaxation time seems to become significantly longer than that of bulk.…”

Quantum Size Effects in the Photonics of Semiconductor Nanoparticles

“…Here a so-called "hot" exciton is formed (see the Scheme, process 1), and this uses up the excess energy in reaction with the crystal lattice ("thermalization" of the exciton) until the energy of the charges in the exciton corresponds to E CB in the case of the electron and E VB in the case of the hole (Scheme, process 2). This mechanism has been called electron-phonon relaxation or thermalization [4,71,219,237,[296][297][298][299]. Further thermalization does not occur, since E g as a rule significantly exceeds the energy of the phonons (E ph » 300 cm -1 ), while multiphonon processes are unlikely.…”

“…In ultrasmall semiconductor crystals, in which the density of states in the conduction band decreases and quantization of the energy spectrum in the permitted bands (more clearly defined the smaller the size of the nanocrystals) occurs as a result of the action of the quantum restriction effect of the charge carriers, it must be expected that thermalization of the charge carriers will be hindered on account of the small probability of small phonon emission and multiphonon processes. However, the results of investigations of semiconductor nanocrystals by femtosecond flash photolysis showed that thermalization of nonequilibrium charge carriers occurs in the nanocrystals just as quickly as (in hundreds of femtoseconds) and sometimes more quickly than in bulk semiconductors [1,4,137,[296][297][298][299][300][301].…”

“…Here, two or more excitons can be simultaneously excited in the nanoparticle, and they then recombine, giving up the excess energy to a third particle and converting it into higher excited states (Auger recombination) (Scheme, process 4) [137,219,296,297,301,302].…”

Design and numerical modeling of normal-oriented quantum wire infrared photodetector array

“…Both of these variant structures will have different optical and electronic behavior and the effects of variant structure (1) are briefly discussed later in this work. Also, somewhat similar physical concepts and device geometry are employed by Xu in his work on highly ordered arrays of carbon nanotubes for use as IR detectors [14]. One requirement of using alumina as a template for electrodeposition of II-VI semiconductors is that nonaqueous based electrodeposition techniques must be used so that the alumina is not dissolved.…”