Comparative analysis of contact resistance and photoresponse in poly(3-hexylthiophene) and poly(3-octylthiophene) based organic field-effect transistors

- Performance of OFETs fabricated using P3HT and P3OT were investigated.
- Estimated values of performance parameters were superior for P3HT OFET.
- Estimated value of contact resistance was one order lower and photoresponse was an order higher in P3HT OFET.
- The observations were attributed to the improved morphology of P3HT over P3OT due to the presence of bulkier alkyl side chain in P3OT

This paper explicitly explores the possibility of tailoring the performance of organic field-effect transistors (OFETs) fabricated using Poly(3-hexylthiophene) (P3HT) and Poly(3-octylthiophene) (P3OT) having different length of alkyl side chain. We observed that the performance of devices fabricated using P3HT were significantly better in comparison to that fabricated with P3OT. The estimated values of performance parameters of P3HT OFET were found to be significantly superior to those of P3OT OFET. Further, an order of magnitude lower contact resistance and higher photoresponse values were evident in P3HT OFETs. Moreover, the gate voltage tunability of photoresponse was also found to be significantly higher in P3HT OFETs highlighting its suitability over P3OT OFETs for photosensitive transistor applications. The results suggest that the alkyl side chain in Poly(3-alkylthiophene)s (P3ATs) is critical for achieving the optimized device performance and can be tailored in order to improve the performance of OFETs.

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