Enhancing optoelectronic performance of organic phototransistors through surface doping of tetra-bromo perylene diimide single crystals

Abstract

Organic phototransistors (OPTs) built from organic single crystals offer distinct advantages over their thin-film counterparts due to their superior charge transport, large surface area, and defect-free molecular arrangement. However, the progress in developing high-performance n-type organic semiconductors has largged behind that of p-type materials, posing a challenge to the advancement of organicelectronic devices. To address this issue, we synthesized novel tetra-bromo-substituted chiral perylene diimides, which self-assembled into single crystals, offering potential of n-type semiconductors. Traditional doping techniques often risk damaging the delicate crystal structure; therefore, we implemented a mild surface doping method using aniline vapor, which preserves the structural integrity of the crystals while significantly enhancing their optoelectronic properties. The doped devices exhibited a remarkable improvement in charge transport, with electron mobility increasing four times to 1.19 × 10⁻² cm² V⁻¹ s⁻¹. Furthermore, the optoelectronic characteristics were significantly improved simultaneously, with the external quantum efficiency increasing over two-fold, and response times becoming notably faster. These enhancements are attributed to the increased charge carrier density and improved exciton separation efficiency following doping. This study demonstrates that our surface doping strategy is a highly effective approach for optimizing the performance of organic single-crystal OPTs, providing a promising pathway for future applications in advanced optoelectronic devices.