Organic Electronics ( IF 3.310 ) Pub Date : 2020-03-02 , DOI: 10.1016/j.orgel.2020.105687 Atul S.M. Tripathi; Rakesh Kumar Gupta; Shubham Sharma; Shuichi Nagamatsu; Shyam S. Pandey
of alkyl chains is a plausible approach to impart the facile solution processability in regioregular poly (poly-3-alkylthioness) (RR-P3ATS) but drastic fall in the conductivity as a function of increasing alkyl chain length restricted the versatile use of its hexyl substituted derivative (P3HT). In this work, fabrication of large area oriented thin films of RR-P3ATs with varying alkyl chain lengths was successfully demonstrated using ribbon shaped floating film transfer method (FTM). Observed decrease in the molecular orientation with increasing alkyl chain length was explained by enhanced alkyl chain inter-digitation as evidenced by trends of d-spacing estimated from the out-of-plane XRD results. In-plane GIXD revealed edge-on orientation in the thin films of all of the P3ATs prepared by ribbon-shaped FTM, which is highly desired for planer charge carrier transport. Parallel oriented thin film of longest alkyl chain (octadecyl) substituted P3AT poly (3-octadecylthiophene) exhibited a field effect transistor (FET) mobility of 1.9 x 10-2 cm2/Vs, which is about 4-5 orders of magnitude higher as compared its previously reported values estimated by time-of-flight and FET methods. Thus, fabrication of thin films by FTM leads to versatile choice of RR-P3ATs for solution processing for FETs using common organic solvents without having any detrimental impact of alkyl chain length on the charge carrier mobility.