The effect of the dielectric end groups on the positive bias stress stability of N2200 organic field effect transistors
Bias stress degradation in conjugated polymer field-effect transistors is a fundamental problem in these disordered materials and can be traced back to interactions of the material with environmental species,[1,2,3] as well as fabrication-induced defects.[4,5] However, the effect of the end groups of the polymer gate dielectric and the associated dipole-induced disorder on bias stress stability has not been studied so far in high-performing n-type materials, such as N2200.[6,7] In this work, the performance metrics of N2200 transistors are examined with respect to dielectrics with different end groups (Cytop-M and Cytop-S). We hypothesize that the polar end groups would lead to increased dipole-induced disorder, and worse performance.[1,9,10] The long-time annealing scheme at lower temperatures used in the paper is assumed to lead to better crystallization by allowing the crystalline domains to reorganize in the presence of the solvent. It is hypothesized that the higher crystallinity could narrow down the range at which energy carriers are induced and thus decrease the gate dependence of the mobility. The results show that the dielectric end groups do not influence the bias stress stability of N2200 transistors. However, long annealing times result in a dramatic improvement in bias stress stability, with the most stable devices having a mobility that is only weakly dependent on or independent of gate voltage.
European Research Council (610115)
Engineering and Physical Sciences Research Council (EP/R031894/1)
European Commission Horizon 2020 (H2020) Marie Sk?odowska-Curie actions (747461)