Optics of colloidal quantum-confined CdSe nanoscrolls

Abstract

Nanostructures in the form of 1.2-nm-thick colloidal CdSe nanoplatelets rolled into scrolls are investigated. The morphology of these scrolls is analysed and their basic geometric parameters are determined (diameter 29 nm, longitudinal size 100 -150 nm) by TEM microscopy. Absorption and photoluminescence spectra of these objects are recorded, and the luminescence decay kinetics is studied. It is shown that the optical properties of CdSe nanoscrolls differ significantly from the properties of CdSe quantum dots and that these nanoscrolls are attractive for nanophotonic devices due to large oscillator strengths of the transition, small widths of excitonic peaks and short luminescence decay times. Nanoscrolls can be used to design hybrid organic -inorganic pure-color LEDs with a high luminescence quantum yield and low operating voltages.

Chiral Optical Properties of Tapered Semiconductor Nanoscrolls

“…This feature allows one to indirectly determine the radius ρ 0 of semiconductor nanoscrolls by comparing their spectra with the spectra of unrolled nanoplatelets and measuring the red shift of the absorption or photoluminescence edge. For example, the red shift of photoluminescence spectra of CdSe nanoscrolls was observed in the experimental work …”

“…For example, the red shift of photoluminescence spectra of CdSe nanoscrolls was observed in the experimental work. 25 Optical activity emerging from perturbing potentials similar to that in eq 11 mostly occurs upon intraband transitions of charge carriers and was thoroughly addressed in our earlier works, 37−39 so in the following we focus on interband transitions between the valence and conduction bands of a semiconductor nanoscroll. As was shown, 40 the absorption rates of band-to-band transitions are practically unaffected by perturbation of the envelope wave functions of charge carriers, with curvature of space metrics being the only significant factor that alters the transition probabilities.…”

“…The theoretically calculated absorption spectrum of a CdSe nanoscroll shown in Figure 3c is similar to the typical experimental spectra of ordinary semiconductor nanoplatelets. 25 It is seen to comprise two exciton peaks HH 1 and LH 1 corresponding to the lowest transitions from the heavy and light hole bands. It also contains the absorption band SO 1 of the electric dipole transitions |1,n y ,n z ⟩ → |1,n y ,n z ⟩ from the spin−orbit hole band, and high energy absorption bands HH 2 and LH 2 of transitions |2,n y ,n z ⟩ → |2,n y ,n z ⟩ from the heavy hole and light hole bands.…”

“…17−21 Nanoscrolls are chiral semiconductor nanocrystals that are formed upon rolling up of nanoplatelets during their synthesis. 22−24 Nanoscrolls resemble nanoplatelets in such electronic properties as strong spatial confinement of excitons in one direction, narrow photoluminescence spectra and short luminescence decay time, 25,26 strong electrooptical response, 27,28 and giant oscillator strengths. 29,30 At the same time, nanoscrolls are essentially chiral nanocrystals whose handedness depends on the direction of winding and that are especially attractive for the described applications due to their low density and relatively large surface area.…”

“…Nanoscrolls are chiral semiconductor nanocrystals that are formed upon rolling up of nanoplatelets during their synthesis. − Nanoscrolls resemble nanoplatelets in such electronic properties as strong spatial confinement of excitons in one direction, narrow photoluminescence spectra and short luminescence decay time, , strong electrooptical response, , and giant oscillator strengths. , At the same time, nanoscrolls are essentially chiral nanocrystals whose handedness depends on the direction of winding and that are especially attractive for the described applications due to their low density and relatively large surface area . Naturally strong optical activity of tapered nanoscrolls can be enhanced even further by doping the nanoscrolls with ionic impurities, by introducing screw dislocations inside them, or by choosing the nanoscroll dimensions to ensure that the quantum states of charge carriers are resonant …”