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The SAM is positioned between ZnO–PbS colloidal quantum dot (CQD) film junction to modify band alignment via the dipole moment of the constituent SAM molecule, and the band tuning may be modified via the density, dipole and the orientation of the SAM molecule.
Colloidal semiconductor nanocrystals, which are also called quantum dots (QDs), consist of ~1–10 nm diameter semiconductor nanoparticles that have organic ligands bound to their surface. These nanomaterials have found applications in nanoscale photonic, photovoltaic, and light-emitting diode (LED) devices due to their size-dependent optical ...
This is in contrast to other quantum dots such as CdSe which must be passivated with an epitaxially matched shell to be bright emitters. In addition to this, lead-halide perovskite nanocrystals remain bright emitters when the size of the nanocrystal imposes only weak quantum confinement .
The Brus equation or confinement energy equation can be used to describe the emission energy of quantum dot semiconductor nanocrystals in terms of the band gap energy E gap, the Planck constant h, the radius of the quantum dot r, as well as the effective mass of the excited electron m e * and of the excited hole m h *.
Larger quantum dots have closer electronic states than smaller quantum dots which means that the energy required to excite an electron from HOMO to the LUMO is lower than the same electronic transition in a smaller quantum dot. This quantum confinement effect can be observed as a red shift in absorbance spectra for nanocrystals with larger ...
Silicon quantum dots are metal-free biologically compatible quantum dots with photoluminescence emission maxima that are tunable through the visible to near-infrared spectral regions. These quantum dots have unique properties arising from their indirect band gap , including long-lived luminescent excited-states and large Stokes shifts .
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The diagram to the right shows edges for an equivalent unit cell with A in the cube corner position, B at the body center, and X at face-centered positions. Four general categories of cation-pairing are possible: A + B 2+ X − 3 , or 1:2 perovskites; [ 8 ] A 2+ B 4+ X 2− 3 , or 2:4 perovskites; A 3+ B 3+ X 2− 3 , or 3:3 perovskites; and A ...