Laser-induced graphene as a versatile platform for colloidal quantum dot heterostructure photodetectors

The growing demand for high-performance, flexible, and low-cost photodetectors has driven research interest in heterostructure-based architectures that integrate materials with complementary optical and electronic properties. In this study, we developed a heterostructure photodetector platform based on laser-induced graphene (LIG) and lead sulfide colloidal quantum dots (QDs). LIG, which is directly patterned on polyimide via laser irradiation, offers scalable mask-free fabrication with mechanical flexibility and excellent conductivity. To enhance charge transfer between the QDs and LIG, solid-state ligand exchange was performed, replacing the long-chain oleic acid ligands with short iodide ligands. This modification significantly improved charge transfer efficiency, resulting in a high photo-to-dark current ratio (>100), responsivity approximately 20 A W^-1 with excellent linearity across a wide range of light intensities, and specific detectivity exceeding 10¹¹ Jones. Furthermore, the versatility of LIG formation was demonstrated through its compatibility with various polyimide substrate formats, proving its potential for fabricating flexible, large-area, and customizable electrode patterns. These findings highlight the application potential of LIG-QD heterostructures as a platform for next-generation flexible optoelectronic devices.