Improving the charge injection in bottom contact organic transistors by carbon electrodes

The electrode/organic semiconductor interface in OFETs is critical to device performance. Traditional metal electrodes often produce an unfavorable interfacial dipole when they are in contact with organic semiconductors, inducing a larger injection barrier. Here, we report an amorphous carbon film formed by a pyrolysis photoresist as the bottom contact source/drain electrode of the OFETs to improve the charge injection. The carbon electrodes show a good conductivity and a work function of -4.67 eV. Although its work function is lower than that of Au, the device shows ten-fold enhancement in mobility compared to Au electrodes. The UPS results further prove that there is a favorable orientation of the interface dipole between the carbon electrode and the DNTT organic semiconductor film, thus reducing the carrier injection barrier and improving the device performance. This finding is beneficial to reducing the contact resistance of the OFET device, which is known as the bottleneck to further scale down the device for high frequency applications.