Emerging research directions for n-type conjugated polymers

In the past decade, -conjugated polymers have been intensively studied in printed optoelectronic applications, such as organic field-effect transistors (OFETs) and organic photovoltaics (OPVs). After years of development, n-type conjugated polymers have exhibited comparable performance to that of their p-type counterparts in both OFETs and OPVs. Apart from OFET and OPV studies, several new research directions for n-type conjugated polymers recently appeared, including organic thermoelectrics, organic electrochemical transistors, organic spintronics, and organic energy storage systems. In these fields, n-type conjugated polymers are either less studied or their device performance lags far behind that of p-type ones. This review highlights the important role of n-type conjugated polymers in these emerging research directions and summarizes the recent progress in the development of n-type conjugated polymers in these new research fields. These fields require n-type conjugated polymers with new properties, such as better mixing with ionized dopants or good water permeability. Thus, new polymer design strategies and device engineering considerations are desired. This review highlights the important role and recent progress of n-type conjugated polymers in several emerging research directions.