Semiconducting organic polymers and Inorganic semiconductor nanocrystals Nir

Semi-conducting organic polymers and Inorganic semiconductor nano-crystals Nir Tessler EE Dept. Technion

Semiconducting Organic Polymers The material: Organic semiconductors = molecular materials small molecules to long polymer chains. Soluble Optoelectronic materials (they come as powder or fibers. We dissolve them in the appropriate solvent and cast them from solution. We usually design it such that after drying we get 0. 1 micron thick solid film) Length scale: Typical layer thickness – 50 -100 nm Inter chain distance ~ 0. 5 nm Nano-Materials

The original motivation Going from green emission to red emission via simple “block” exchange Chemistry LEGO n + O + CN O O = O CN n Wavelength (nm) Organic LEDs one of the best sources for visible light

The first known application Organic (“plastic”) Displays A proof for the material maturity:

Examples from the lab Organic transistor switching organic LED Blue organic LED

A “Problem” Polymers emit visible light only! But optical communication elements operate with near infrared light can’t use the low cost “plastic” technology? OK – Lets mix Pb. Se 5 nm 5 nm In. As/Zn. Se O Conjugated polymers Me. O n

Mix It Organic polymer in solution Inorganic semiconductor nano-crystals in solution n=o=0. 5 Mix two solutions to get the right composition

Using transmission electron microscope we can also “see” the 5 nm crystals in the polymer matrix (i. e. the solid film)

After mixing, the plastic polymer do not emit visible light and instead the inorganic nanocrystals emit in the near infrared (telecomm bands) Indium Arsenide nanocrystals Lead Selenide nanocrystals A nice feature – by changing the size of the nanocrystal it is possible to tune the emission to a desired wavelength

What happens when you place such a composite film between two electrodes? CaAl (cathode) Current/Energy is first injected into the Polymer polymer O - Me. O V n Energy/Charge Transfer to the nanocrystal + Light Emission PEDOT/ITO (Anode) Glass

The potential Impact The telecomm experts say that for the fiber to the home to happen they need low cost components that can be afforded by any household. Use “plastics”

Thanks