Decyloxy-substituted BTBT derivatives for highly efficient and stable thin-film organic (opto)electronic devices

Abstract

Rational molecular design can yield novel organic semiconductors (OSs) with superior properties. In this study, we show that introduction of oxygen atoms in the terminal alkyl groups of diphenyl-substituted BTBT derivatives improves a number of important properties of the material. Specifically, we synthesized 2,7-bis(4-decyloxyphenyl)[1]benzothieno[3,2-b][1]benzothiophene (DOPBTBT) and compared it with its oxygen-free counterpart DPBTBT. We show that the oxygen-containing molecule is considerably more stable against thermal oxidation, and the corresponding crystals exhibit no phase transitions from room temperature up to 150 °C. The photoluminescence quantum yield is also higher for this molecule and reaches 48%. The charge-carrier mobility in thin films is about three times higher for DOPBTBT and reaches 0.74 cm² V⁻¹ s⁻¹; moreover, it is stable in the course of about one month under ambient conditions. OFETs based on the monolayer of DOPBTBT molecules demonstrate a high charge-carrier mobility of 1.1 cm² V⁻¹ s⁻¹, which is among the largest observed for monolayer devices. Finally, we show that DOPBTBT can be used in light-emitting and photo transistors. The results obtained highlight that addition of oxygen atoms into the terminal alkyl substituents of BTBT derivatives is a promising tool for molecular design towards high-mobility and stable organic semiconductors for organic optoelectronic devices.