SiO2 layer hepls PEDOT:PSS to make a good contact with Silicon. It has got a thickness of 2-3 nm. Then how a p-n junction will form if semiconductors are apart?
Dear Raju ,
you are welcome!
The organic semiconductor PEDOT-PSS forms with the single crystalline n- type silicon substrate a p-n hetero junction. If the organic semiconductor PEDOT-PSS is deposited directly on the silicon surface, there will be very large surface states which change the contact difference of potential of the junction and also acts as effective recombination centers. Such surface defects are well studied and well known.One effective method to overcome the effect of surface state is to passivate them by either hydrogen bonding or better a very thin oxidation layer. It is also well known that the interface state at the Si/SiOx is very reduced compared to the bare silicon surface. Even this oxide layer is formed as native oxide on the silicon surface when it is subjected to environment.
The organic p type semiconductor acts a wide gap emitter layer which is very effective in reducing the reverse maturation current and thereby reduces the dark current leading to high open circuit voltage.
However the thin passivation oxide layer must be very thin such that it is tunnelable.
Therefore is it made with 2-3 nano meter thickness.
This why such hybrid cells yield relatively high efficiency.
For more information please visit the link:
http://ac.els-cdn.com/S1876610215008152/1-s2.0-S1876610215008152-main.pdf?_tid=176f4cbc-f502-11e5-a8b8-00000aacb361&acdnat=1459182683_c111d57820c93d74a773e44aee333061
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Dear Sir,
Thank you for your reply. I understood your point. Still I have a doubt. With that thickness of oxide layer (2-3 nm), How p type will diffuse in n type? Advised paper also does not clear it.
Dear Raju,
welcome again,
When the thicness of the oxide layer is so small it does not impede the motion of the motion of holes from the PEDOT-PSS semiconductor to the n-type silicon substarte. The holes can cross the potential barrier of the oxide by a transport mechanism called tunneling.The tunneling rate increases as the thicness of the oxide decreases.
The same applies for the motion of the electrons from the n-side to the p-side.
The major effect of the the ultrathin oxide layer is to passivate the the surface state on the silicon substrate.It slightly affects the transport of holes and electrons across it.
wish you success
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