Microphase separation-promoted crystallization in all-conjugated poly(3-alkylthiophene) diblock copolymers with high crystallinity and carrier mobility

Abstract

The crystallinity of all-conjugated diblock copolymer, poly(3-butylthiophene)-b-poly(3-dodecylthiophene) (P3BDDT), with varied block ratios was significantly enhanced by a “two-step” thermal annealing treatment. The resulting P3BDDT exhibited an attractively high crystallinity of ∼35%, which is a 3-fold enhancement over those of its homopolymer counterparts. The space-charge limited current (SCLC) mobility measurement revealed that the carrier mobility of the highly crystalline P3BDDT film was increased to as high as ∼8.4 × 10⁻³ cm² V⁻¹ s⁻¹, exceeding the highest SCLC mobility of poly(3-alkylthiophene) homopolymer films reported in previous work (i.e., ∼1.6 × 10⁻³ cm² V⁻¹ s⁻¹). DSC, XRD, AFM and SAXS characterizations demonstrated that the interplay of crystallization and microphase separation during the “two-step” thermal annealing treatment plays a key role in the improvement of P3BDDT crystallinity.