In situ PTCDI-aided lateral crystallization of benzothieno-benzothiophene derivative for photoresponsive organic ambipolar devices

Abstract

Here, we report a laterally stacked organic crystal active layer formed from the mixed solution of a perylene diimide derivative (PTCDI-C₅) and a benzothieno-benzothiophene derivative (C₈-BTBT) through a solution process called in situ PTCDI-aided lateral crystallization, where PTCDI-C₅ serves as an n-channel semiconductor as well as a template for the crystallization of the p-channel C₈-BTBT. We found that the crystal formation was strongly influenced by the composition of the mixed solution of PTCDI-C₅ and C₈-BTBT, and ambipolar laterally stacked crystals could be prepared after optimizing parameters of the solution composition, such as ratio and total concentration. The devices fabricated based on the stacked crystals exhibited well-balanced ambipolar charge transport behavior, with a mean mobility of 3.5 × 10⁻² cm² V⁻¹ s⁻¹ for electrons and 7.6 × 10⁻² cm² V⁻¹ s⁻¹ for holes, and showed responsivity as high as 3.7 A W⁻¹, with a maximum photosensitivity of 686 under white light illumination. We successfully implemented these transistors in a complementary-like inverter that exhibited clear ambipolar voltage transfer behavior in the first and third quadrants with the gain of 10. Using this in situ lateral crystallization method, it is possible to prepare composite semiconducting layers with well-balanced ambipolar charge transport and photodetection capability in the desired wavelength range by the appropriate selection of component materials.