Resolving the High-k Paradox in Organic Field-Effect Transistors Through Rational Dielectric Design

Dielectric materials with high relative permittivity, i.e., high-k dielectrics, are in great demand for application as gate dielectric for the development of field-effect transistors operating at low voltages. However, a high-k gate dielectric does not always produce favorable outcomes, particularly in field-effect transistors based on organic semiconductors (OFETs). Contradicting experimental results have been reported, with some studies showing compromised OFET performance, while others demonstrate enhanced performance when using high-k gate dielectrics. Currently, no comprehensive or systematic study has been conducted to compare or integrate these conflicting results. As a result, the relative validity and broader implications of these conflicting findings remain uncertain. Here, the effects of high-k gate dielectrics with systematically varied dielectric constants on OFET performance are systematically investigated and the inconsistencies in the literature are resolved. By employing a highly miscible high-k polymer blend system, it is demonstrated that both positive and negative correlations of dielectric constant and field-effect mobility exist in different semiconductor systems. These results provide a strategy to rationally design organic transistors that incorporate high-k dielectrics, without compromising the field-effect mobility due to the broadening of the density of states.