Nitrogen‐Doped Graphene Quantum Dots and Monolayer MoS ₂ ‐Based 0D/2D Unipolar Heterojunctions as a Broadband Photodetector

This study presents a broadband photodetector operating from the near‐infrared (NIR) to the ultraviolet (UV) region, based on a 0D/2D unipolar heterojunction. The heterostructure, composed of nitrogen‐doped graphene quantum dots (N‐GQDs) and molybdenum disulfide (MoS ₂ ), was fabricated via a simple one‐pot hydrothermal method. Broadband detection is enabled by combining the UV‐absorbing N‐GQDs with MoS ₂ , which absorbs visible and NIR light. The Fermi level alignment between the two materials creates a unipolar junction, generating a localized electric field that promotes efficient separation of photogenerated carriers. The fabricated device exhibits responsivities of 189, 95, and 845 mA W ⁻¹ in the NIR, visible, and UV regions, demonstrating its highest sensitivity within the UV spectrum. The underlying photodetection mechanism is explained through band alignment theory and the role of trap states. This cost‐effective and scalable 0D/2D heterojunction design shows significant potential for applications in optoelectronics, security systems, and wearable devices.