Charge Transport Of Polymer Field Effect Transistors Based On Spontaneous Doping

The organic field-effect transistor(OFET)based on conjugated polymer has attracted extensive attention due to its great potential in the application of large-area flexible electronics.Since the performance of OFETs largely depends on the charge transport,the exploration of charge transport is an indispensable part of device performance improvement.The well-aligned dipole moments at the dielectric-semiconductor interface modulate the charge transport from ambipolar to unipolar in OFETs,which is called spontaneous P doping.The unipolar transport can make OFETs more suitable for complementary circuits,so it is particularly important to study spontaneous doping.Since the spontaneous doping is related to the annealing temperature of the dielectric layer and whether it has direct contact with the organic semiconductor layer,detailed studies are carried out.First,OFETs with top-gate,bottom-contact strcuture were fabricated by using DPPT-TT as semiconductor and fluorinated polymer CYTOP as dielectric.By changing the annealing temperature of DPPT-TT and analyzing the variation of device properties under different annealing temperatures,the results show that the performance of DPPT-TT is less affected when the annealing temperature between 100 ℃ and 150 ℃.Second,OFETs with top-gate,bottom-contact structure were fabricated by using DPPT-TT as semiconductor and fluorinated polymer CYTOP as dielectric.By changing the annealing temperature of the dielectric layer,the variation of the device performance under different annealing temperatures was analyzed,it was found that the spontaneous doping strength of the device was greatest when the annealing temperature of the dielectric layer was 100 ℃.Third,OFETs with top-gate,bottom-contact structure were fabricated by using DPPT-TT as semiconductor,single-layer PMMA,single-layer CYTOP and double-layer(PMMA+CYTOP)as dielectric,respectively.The electrical characteristics and the parameters of the devices with different dielectric layers were compared.The experimental results showed that,the spontaneous doping can only be produced when the device with a fluorinated polymer dielectric is in direct or indirect contact with the semiconductor layer.