P3HT:PCBM blend based photo organic field effect transistor

• We have investigated organic bulk hetero-junction based MESFET type photo-OFET.
• Device has shown low voltage operation.
• Device has followed p-type operation mode of a typical ambipolar FET.
• Field effect mobility was found higher as compared to reported organic MESFETs.

In this work, we have fabricated photo organic field effect transistor using the blend of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C61-butyric acid methylester (PCBM) as active layer. Transistor was fabricated in MESFET type configuration with top gate and bottom drain source contacts on glass substrate. Drain and source contacts were made using Silver (Ag) whereas gate contact was made by depositing Aluminum (Al) on the active layer. Active layer showed Ohmic type contact with drain/source electrodes and Schottky type contact with gate electrode which was discussed with help of energy band diagram. I–V characteristics of the device were investigated under dark and UV–Vis illumination, and these were found similar to p-type mode I–V characteristics of a typical ambipolar field effect transistor. Further, device has shown low voltage operation with weak saturation trend under illumination. Field effect mobility and photo responsivity values of the device were found higher as compared to reported organic photo-MESFETs. Realization of such low voltage devices will provide potential for the development of low cost large area flexible sensor arrays and other low power electronic devices in future.

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