I am working on silver nanoparticles synthesis. I want to make use of it in oleds. Please tell me how to do it. I can also collaborate.
Silver nanoparticles would not be useful for OLEDS. You need a semiconducting material, either inorganic or polymers....... silver nanoparticles even if you use as a coating in one of the electrodes(injection), it still would not be great since it oxidises very quickly
Silver is a stable electrode for an OLED device. Our lab has reported a highly efficient printed OLED device incorporating silver paste (a formulation of silver nanoparticle). After sintering, silver paste can become highly conductive making it an ideal cathode metal that can be ink-jet printed. The critical point here is the sintering temperature. OLED device cannot bear temp higher than 150degC.
So if your silver nanoparticle can be deposited into thin film by spin-coating or ink-jet-printing, and it demands low temperature sintering or even no thermal sintering to make it conductive, it will be a great candidate. We are also looking for such kind of solution-processable silver.
See our paper in the link.
http://dx.doi.org/10.1038/ncomms2971
For an OLED to work, one requires an emitting layer. The molecule/material that can be used as an emitting layer need to possess a band gap.
Typical Structure of an OLED - Bottom electrode(Anode) / Hole transport Layer (HTL) / Emitting Layer (EM) / Electron Transport Layer (ETL) / Top Electrode (Cathode)
Requirements for the design of an OLED
1. Choose a bottom electrode (Anode) whose work function matches or is close to the HOMO of Hole transport layer.
2. Choose a top electrode whose work function matches or is close to the LUMO of Electron transport layer
If the work function of bottom electrode is close to the HOMO of HTL then the barriers will be low. Similarly top electrode work function must be close to LUMO of ETL for barriers to be low.
3. One of the electrode has to be transparent so that light comes out of the device.
e.g. Typically ITO - is used as a bottom transparent electrode.
4. HTL must have higher mobility for holes than electrons. A good HTL must have very high mobility for holes and very low mobility for electrons.
5. ETL must have higher mobility for electrons than holes. A good ETL must have very high mobility for electrons and very low mobility for holes.
6. EM should be a luminescent material with a band gap and high fluorescence quantum yield. Band gap decides the color of light emitted by the OLED.
Sometimes one material can play multiple roles i.e., one material can act as an emitting layer (EM) and ETL.
Generally if the barriers for hole injection and/or electron injection are large then the device will have a high turn voltage in the I-V curves and also high EL onset voltage.
If the Hole mobiltiy of HTL and electron mobility of ETL are different then one has to balance them by varying the thickness of the layers provided the barriers for hole injection at bottom electrode / HTL interface and the barrier for electron injection at top electrode / ETL interface are same.
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