Enhanced photoconductivity of semiconductor polymers using graphene nanoflakes

We have examined the effect of the addition of graphene nanoflakes (GNs) to improve the field-effect mobility of poly(3-hexylthiophene) (P3HT)-based field-effect transistors (FETs). We observe that the FET mobility increases up to 0.02 cm²/Vs at GNs concentration of 0.06 mg/mL. The remarkable increase in FET mobility can be ascribed to the incorporation of highly conducting and highly ordered graphene flakes, which acts like conducting bridges between the P3HT molecules. With further increasing the concentration of GNs, the mobility and I_on/I_off ratio starts to decrease, due to mismatching of the energy levels of graphene and P3HT. The effect is further evidenced from the time-of-flight photocurrent (TOFP) measurements, in which the transit time (t_tr) of the charge carriers are shifted to shorter times in blended layers compared to pristine P3HT. Further, we have analyzed time-resolved photocurrent variation on these samples in terms of hopping transport model using Monte-Carlo (MC) simulations within the framework of Gaussian disorder. These studies reveal that the addition of GNs causes improvement in mobility and reduces the extremely slow carriers and uniform arrival of the charge carriers. More here.