optical and electrical properties
Quantum confinement effects
luminescence of semiconductor
CdSe nanoparticles of different sizes
광반도체 재료로서 우수한 특성을 가짐
(Quantum confinement effects)
양자 구속효과에 대란 상태밀도 a. 벌크(3D) b. 양자우물(2D) c. 양자점(0D)
Quantumdot LEDs, LED
기존의 LED와 Quantumdot LED
What is LED?
Light Emission Diode
Using P-N Junction
Wave length is defined
by Element’s Band Gap
Compound Red, Green, Blue
↓
Express Color!(white…)
Core : 2~10 nm
- Ⅱ-Ⅳ element (CdSe, CdTe, Cds)
Shell
- metallic molecular plating(ZnS, ZnSe)
Polymer Coating
- To disperse in the aqueous solution
Quantumdots are particles of semiconductor material with the size so small that the electron energies that can exist within them are limited. These energy levels, defined by the size of quantumdots, in turn define the bandgaps. The dots can be grown to any needed size, allowing them to be tuned across a wide variety of bandgaps without changing the underlying material or construction techniques
Free(wannier-mott)
Radius >> a(exciton Bohr radius)
Small binding energy :~ 0.01 eV
Delocalized states
Move freely through crystal
(semiconductors)
Tighthly-bound(Frenkel)
Radius ~ a(exciton Bohr radius)
large binding energy : 0.1 -1.0 eV
localized on one lattice site
Moving by hopping
(insulators and molecules)
Eadd = △E + Ec
Ec = e2/C
C = 2πεεod
(depend on geometr