Colossal Vacancy Effect of 2D CuInP2S6 Quantum Dots for Enhanced Broadband Photodetection

Abstract

Band engineering is an effective way to tune the physical and chemical properties of materials, leading to significant performance improvement. Herein, the first two-dimensional (2D) quaternary quantum dots (QDs), CuInP2S6 (CIPS) QDs, were successfully fabricated by the lithium intercalation method with a high yield of ∼29%. Importantly, the tuned band structure of CIPS was achieved by forming colossal lithium-induced phosphorus and sulfur vacancies, endowing CIPS QDs with stronger and broader optical absorbance, as well as higher conductivity. Therefore, CIPS QDs exhibit outstanding intrinsic optoelectronic performances toward broadband photodetection with a broadband photoresponse from 405 to 1550 nm, a photoresponsivity of 22.9 A/W, a detectivity of 3.65 × 108 Jones, and a response speed of 60 ms. Especially, such excellent performances can be realized in a simple device structure and ambient air, exceptionally different from most 2D QD-based photodetectors requiring a heterostructure, gate voltage, or vacuum condition. In addition, CIPS QDs retain outstanding photoresponse on curving flexible substrates and in imaging applications. This work provides a unique venue for band structure tuning to effectively manipulate materials’ optoelectronic properties and functionalities.