A first-principles study of optoelectronic properties and electric field modulation in PbS quantum dot/graphene hybrid systems

Abstract

A hybrid low dimensional system composed of quantum dots (QDs) and graphene combines the excellent photoresponsive properties of QDs with the ultra-high carrier mobility of graphene, which provides a promising platform for the next generation of high-performance photodetectors and image sensors. However, further research is needed before this design can be truly optimized and eventually commercialized. In this work, the optoelectronic properties of a series of PbS QD/graphene systems are studied using first-principles calculations based on density functional theory (DFT). The interaction between different halogen-passivated low-index crystal facets of a PbS QD and monolayer graphene is analyzed from the perspectives of electronic states, wave function coupling, and interface charge redistribution. The hybrid system with the strongest interaction is identified and the reason is discussed. It is shown that there is enhancement of the interaction between non-polarized crystal facets of the PbS QD and graphene. Additionally, it is found that the variation of the direction and intensity of an external electric field can approximately linearly shift the energy levels of the hybrid system and affect the charge transfer between the two components, which may be very useful for manipulating the performance of the device developed from the system. This study helps understand the optical properties of the PbS QD/graphene system and provides insights for its future optimization.