Promoting phototransistor performance by utilizing solution epitaxy templated organic semiconductor films†

Abstract

The quality of organic semiconductor films plays a crucial role in carrier transport and the overall performance of organic phototransistors (OPTs). Various approaches have been explored to enhance the morphology of organic films, and one effective method involves using crystalline templates with large domain sizes to promote the growth of the upper active films. However, strategies for obtaining continuous and uniform template layers over large areas are still in high demand. Herein, we employ a “solution epitaxy” method to fabricate a uniform C₃₂H₆₆ crystalline film as the template layer, facilitating the growth of the organic semiconductor 2,8-difluoro-5,11-bis(triethylsilylethynyl)anthradithiophene (diF-TES-ADT) over a large area. Our results demonstrate that the morphology of the epitaxial films strongly depends on the morphology and thickness of the template layer. By optimizing the template layer, we successfully obtain terraced-like organic semiconductor films with excellent crystallinity with large domain sizes. These epitaxially grown films are then employed as carrier transport channels in OPTs, leading to the development of high-performance devices with a sensitivity of 3.74 × 10⁶ and a responsivity of 6.2 × 10³ A W⁻¹. Furthermore, the obtained phototransistors show promising potential for emulating synaptic behavior with their dependence on illumination power intensity and UV light addition time. This finding provides a feasible strategy for obtaining high-quality organic films with efficient charge transport and high photoresponse properties.