Luminescence of CdSe/Al2O3 quantum wires at high photoexcitation levels

Simple Surface-Trap-Filling Model for Photoluminescence Blinking Spanning Entire CdSe Quantum Wires

“…Although it is possible for excitons, electron−hole pairs, or single charge carriers, either electrons or holes, to become trapped in surface-trap sites, and a complete theory should account for the probabilities for each, we have chosen to include only the trapping of excitons in this model for a couple of reasons. The binding energies of the photogenerated 1D excitons are quite large in CdSe QWs, >100 meV, , and a significant amount of energy would be necessary to separate the electron−hole pairs even at room temperature. Additionally, previous studies indicate that continued charging with irradiation does not occur in CdSe QWs; the total steady-state electron density on single CdSe QWs with continuous irradiation has been estimated to be at most 0.45−1.2 μm -1 along the length of the QW .…”

Quantum Size Effects in the Photonics of Semiconductor Nanoparticles

“…The restricted free motion of the exciton in the volume of semiconductor nanoparticles leads to an increase in the energy of coulombic interaction between the electron and hole forming the exciton, i.e., to an increase in the bond energy of the charges in the exciton E ex [4,6,17,50,219], which can be calculated from the following expression [4,17]:…”

“…A similar result was obtained in [39,40,44,48,107] for CdS, CdSe [44,204,210,219,293], CdTe [44,51], and CuCl [4] nanocrystals. The oscillator force of the exciton transitions of semiconductor nanoparticles, placed in a dielectric matrix (a nonconducting polymer, glass, silica gel, etc., satisfying the condition e >> e 0 , where e and e 0 are the dielectric constants of the semiconductor and of the dielectric matrix respectively), can increase not only on account of size quantization but also as a result of the so-called "dielectric amplification" [2,17,50,65], which arises as a result of "concentration" of the electric field of the electron and the hole forming the exciton in the volume of the nanoparticles on account of the significantly smaller dielectric constant of the semiconductor compared with the dielectric. In ultrasmall semiconductor crystals most of the force lines of the electric field binding the electron and the hole fall beyond the limits of the nanocrystal, and with the above-mentioned relation between the dielectric constants of the semiconductor and the nanoparticles decrease in the size of the nanoparticle leads to strengthening of the coulombic interaction between the charges in the exciton and to increase in the oscillator force of the exciton optical transitions.…”

“…However, in the case of the nonmobile or poorly mobile center of masses of the exciton their sum is significantly less than the value of the first term of the equation, and they are usually disregarded in approximate calculations. The results of theoretical and experimental investigations of the dependence of E on the size of the semiconductor nanoparticle for CdS [10,23,35,[37][38][39][40][41][42][43][44][45][46], CdSe [4,[47][48][49][50], CdTe [43,44,51,52], HgTe [53], ZnO [23,35,[53][54][55][56][57], PbS [17,23,33,37,58,59], CuS [60,61], ZnS [37], PbSe [33,59,[62][63][64], PbI 2 [4], GaAs, InSb [35], InP [65], Si …”

Enhanced photoluminescence of corrugated Al2O3film assisted by colloidal CdSe quantum dots

“…Combining corrugated Al 2 O 3 films with CdSe quantum dots to form a heterojunction may affect the charge transfer direction due to their differential energy level structure at the jagged conduction band (CB) and valence band (VB) positions [28,29]. Here, we need to consider an important issue about the spacing between the corrugated Al 2 O 3 film and the CdSe QDs.…”