Defect-mediated carrier trapping and nonradiative recombination in two-dimensional sliding ferroelectrics

Two-dimensional (2D) sliding ferroelectrics have garnered significant attention as potential candidates for next-generation electronic devices, including non-volatile memories and optoelectronic neuromorphic devices. However, the impact of defects on photoinduced carrier dynamics in these materials remains largely underexplored. Here, we systematically investigate the role of sulfur (S) vacancies in rhombohedral-stacked MoS2 bilayers and their influences on carrier trapping and nonradiative recombination. Our results demonstrate that S vacancies introduce localized electron trap states within the bandgap. While suppressing direct recombination, these trap states open a highly efficient two-step nonradiative channel. This new pathway, mediated by low-frequency phonon modes, accelerates the overall recombination, reducing the carrier lifetime. The findings are crucial for engineering defects and controlling carrier dynamics in 2D ferroelectrics. This study not only advances fundamental understanding of defect-related processes in MoS2 bilayers but also paves the way for the design of more efficient optoelectronic devices.