Spray-coating semiconducting conjugated polymers for organic thin film transistor applications

Abstract

We herein present the results from our study of spray-coated poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-bithiophene] (F8T2) semiconducting polymer films for organic thin film transistor (OTFT) applications. Optimized spray-coating parameters were performed for deposition of F8T2 layer on Si/SiO₂ substrate treated with self-assembled monolayers (SAMs) of organosilane compounds. OTFTs fabricated from general spin-coating on the same substrate were also tested to evaluate the quality of active F8T2 layer. Comparable OTFT electrical performances can be obtained for both cases even through the spray-coated devices have high surface roughness and low overall homogeneity. The spray-coated F8T2 OTFTs on the SAMs-modified substrate exhibit a maximum hole mobility of ∼7.8 × 10⁻³ cm² V⁻¹ s⁻¹ and ON/OFF ratios of over 10⁵. These results confirm that the spray-coating method is a powerful tool in production of reliable and reproducible OTFTs, displaying a great potential for other solution-processable organic (opto-)electronics devices.