Recent techniques and strategies in development of high mobility diketopyrrolopyrrole (DPP)-based polymer for organic transistors

For the past few years, organic field-effect transistors (OFETs) have attracted interest because of improvements in the charge carrier mobility and lifetime stability. OFETs based on π-conjugated polymers are of interest for complementary-like electronic circuits. A lot of research has been done on the development of a range of high-performance conjugated polymers with p-type, n-type, and ambipolar properties. One such material is diketopyrrolopyrrole (DPP)- based conjugated polymer. The electron deficient property of DPP, its planar backbone, and intermolecular hydrogen bonding results in materials with strong π- π stacking interactions. It was found that the fused aromatic rings such as DPP and thieno(3,2-b)-thiophine form a large orbital overlapping area, which is useful for charge carrier transport. Similarly, applying side chain engineering and molecular design strategy by coupling diketopyrrolopyrrole with diketopyrrolopyrrole in an alternating fashion results in a copolymer with exceptional absorption characteristics (~1100 nm) and field effect mobility values of greater than 1 cm²V⁻¹s⁻¹. DPP copolymerization with electron donor moieties, like thiophene, selenophene, naphthalene, bithiophene, benzothiadiazole, vinylene and thieno-thiophene, results in high charge carrier mobility. Moreover, the hole mobility higher than 10 cm²V⁻¹s⁻¹ has been achieved based on donor-acceptor (D-A) copolymer with long hexadecyl side-chains. Thus, the high carrier mobility of DPP makes it an excellent candidate to obtain high performance OFETs for use in electronic circuits.