Impact of Crystal Domain on Electrical Performance and Bending Durability of Flexible Organic Thin-Film Transistors with diF-TES-ADT Semiconductor

Abstract

In this study, we examined the impact of crystal domain on the electrical performance and durability of flexible organic thin-film transistors (OTFTs). To analyze this, we fabricated the OTFTs on a polyimide substrate using 2,8-difluoro-5,11bis(triethylsilylethynyl)anthradithiophene (diF-TES-ADT) as the organic semiconductor. To examine the influence of the film morphology and crystallinity on the electrical characteristics of OTFTs, we dissolved diF-TES-ADT in chlorobenzene and toluene solvent, annealed it at different temperatures, and then evaluated its electrical performances. The optimum annealing temperature of the diF-TES-ADT OTFTs was determined through the comprehensive analysis of the electrical parameters. The film morphology and crystallinity of organic semiconductor as a function of temperature were examined using the technical measurement analysis such as the atomic force measurement, X-ray diffraction and polarized optic microscopy. Furthermore, we demonstrated the electrical degradation of the device under prolonged bending cycles and observed the effect of bending stress on the electrical performance of OTFTs. The size of the crystalline domain and surface morphology indicated a slower deterioration of OTFT performance with an increase in the number of bending cycles. It was approved that the crystal grain size and morphology of organic semiconductor may not be critical factors determining the electrical performance of OTFTs, however, the electrical durability against bending stress was significantly degraded by these factors. We speculate that the smaller grain sizes and directionally-grown crystalline structure are highly vulnerable to bending stress, resulting in increased occurrence of void cracks and structural defects.

Graphical Abstract