Synthesis and Electrical Properties of Diketopyrrolopyrrole-Based Block Copolymer with Tunable Molecular Weight of Poly(styrene)

To enhance the hole mobility of diketopyrrolopyrrole-quaterthiophene conjugated polymer, P(DPP-4T), where electron-deficient and electron-rich units alternate along the main chain, we synthesized a series of block copolymer based on P(DPP-4T) with electrically inert poly(styrene) (PSt) with tunable molecular weight. Hole mobilities determined by space-charge limited current measurements were enhanced by the introduction of PSt blocks confirming that our original strategy that the introduction of electrically inert block to semiconducting polymers enhances the career mobility is true for this low band gap polymer. Although the exact origin was unclear, the introduction of PSt with molecular mass of 2,000 was most effective.