Inverted annealing enhanced performance of organic thin-film transistors and phototransistors based on 2-(4-dodecylphenyl) [1]benzothieno[3,2-b]benzothiophene

Thermal annealing is an effective process for regulating the arrangement of liquid crystalline molecules to realize high performance devices. Although, extensive research has been conducted on the development of this technique in recent years, it is still challenging to fine-control the molecular packing and arrangement in thin films. Herein, we propose an inverted annealing approach to address this issue, which successfully improves the performance of organic thin film transistors based on 2-(4-dodecylphenyl) (Bucella et al., 2015) [1]benzothieno[3,2-b]benzothiophene (C12-Ph-BTBT) with ~25% increase in mobility compared to the counterparts with conventional annealing. In addition, the photoelectric properties of C12-Ph-BTBT based phototransistors treated with inverted annealing display a similar improvement, with an enhancement in the highest photoresponsivity from 461.6 A/W for conventionlly annealed devices to 541.7 A/W under the incident beam intensity of 179.2 μW/cm2. This device improvement is mainly ascribed to the gravity induced alignment of C12-Ph-BTBT molecules due to their soft nature at high temperature. Our results provide an effective way to improve the performance of organic electronic devices based on liquid crystalline molecules.