My device structure is ITO/PEDOT:PSS/Active layer/Al. Here i am using p3ht-cnt composite as the active layer. During dark i-v measuring i am not getting the usual diode characteristics for the device. I am getting a linear curve instead.
What may be the possible cause ?
Is it the thickness of the active layer playing any role here ?
Hi Prakash,
It is highly likely that your devices are shunted. The Al anode may direct connect to ITO cathode. The reason may be the porous PEDOT or active layer. You may want to try (1) clean ITO substrate (by UV-Ozone or oxygen plasma) before depositing PEDOT; (2) filter PEDOT solution; (3) filter active layer solution; (4) deposit an electron blocking material (PCBM, C60, etc.) before Al
Thickness of the active layer is not that important, but you may still want to make sure the active layer is conformally coated ITO/PEDOT substrate and Al and ITO are totally isolated.
Good luck on your experiment.
Dear Praash,
What has been said by Zhaoning is okay and cover most of the causes not to have diode lie characteristics of organic solar cell structure. But in order to be specific you it is advisable to display the measured I-V characteristics.
wish you success.
To gain more insight into this problem, you would benefit from a thermographic investigation (dark lock-in thermography, DLIT), because this is a first step to locate the shunt position. Afterwards, you could use optical and/or electron microscopy to further investigate the shunted position in order to find out what went wrong.
You should determine the carrier concentration of your CNTs. The length of CNTs sometimes encourage shunting. Concentration of CNTs is also anther factor you should consider.
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