2-Aminoanthracene Crystallization in Its Compatible Polystyrene Block: RAFT Synthesis and Enhanced Charge Retention in Pentacene Transistor Gate Dielectrics

Abstract

We synthesized polystyrene-block-polyanthrylaminomethylstyrene (PS-b-PAAS) via the RAFT reaction and side chain modification, where the PAAS block is 50%. By blending 2-aminoanthracene (2AA) with PS-b-PAAS, the coaggregation behavior of the PAAS block and 2AA within the thin film was observed by optical microscopy (OM) and X-ray diffraction. At 5 and 10 wt % 2AA within the thin film, OM results showed a clear morphological difference between the PS matrix and PS-b-PAAS matrix. Differences in the 2AA excited-state lifetimes in these matrices were also established by using transient absorption spectroscopy (TAS). Blends were used as gate dielectrics in the pentacene transistors. We compared characteristic voltage (V c, an indicator of threshold voltage) before and after charging of PS-b-PAAS blended with unsubstituted PS and both polymers individually blended with 2AA. For blended PS-b-PAAS and PS, as the concentration of PS-b-PAAS increases, the decreased Vc especially with negative charging of the pentacene indicated a larger concentration of charge carriers induced by the dielectric film. The charging experiments also revealed that the unique structure formed by the 2AA/PS-b-PAAS blend significantly affected the charge storage capability of organic field-effect transistors (OFETs). This work demonstrates the novel coaggregation structure in the dielectrics and furthermore its impact on charge storage capability in pentacene OFETs.