The charge carrier transport of conjugated polymer thin film is mainly decided by the crystalline domain and intercrystallite connection. High-density tie-chain can provide an effective bridge between crystalline domains. Herein, the tie-chain connection behavior is optimized by decreasing the crystal region length (lc ) and increasing the crystallization rate. Poly[4-(4,4-bis(2-octyldodecyl)-4H-cyclopenta[1,2-b:5,4-b']dithiophen-2-yl)-alt-[1,2,5]-thiadiazolo[3,4-c]pyridine] (PCDTPT-ODD) is dissolved in nonpolar solvent isooctane and high ordered rod-like aggregations are formed. As the temperature increases, the changes in solution state and crystallization behavior lead to three different chain arrangement morphologies in the films: 1) at 25 °C, large and separated crystal regions are formed; 2) at 55 °C, small and well-connected crystal regions are formed due to faster crystallization rate and smaller nucleus size; 3) at 90 °C, the amorphous film is formed. Further results show that the film prepared at 55 °C has a smaller crystal region length (lc , 7.6 nm) and higher tie-chains content. Thus, the film exhibits the best device mobility of 2.3 × 10-3 cm2 V-1 s-1 . This result shows the great influence of crystallization kinetics on the microstructure of conjugated polymer films and provides an effective way for the optimization of the intercrystallite tie-chain.
Keywords: D-A conjugated polymers; crystal region lengths; crystallization rates; tie-chain connection.
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