Two-dimensional (2D) transition metal dichalcogenide (TMDC) monolayers, a class of ultrathin materials with a direct bandgap and high exciton binding energies, provide an ideal platform to study the photoluminescence (PL) of light-emitting devices. Atomically thin TMDCs usually contain various defects, which enrich the lattice structure and give rise to many intriguing properties. As the influences of defects can be either detrimental or beneficial, a comprehensive understanding of the internal mechanisms underlying defect behaviour is required for PL tailoring. Herein, recent advances in the defect influences on PL emission are summarized and discussed. Fundamental mechanisms are the focus of this review, such as radiative/nonradiative recombination kinetics and band structure modification. Both challenges and opportunities are present in the field of defect manipulation, and the exploration of mechanisms is expected to facilitate the applications of 2D TMDCs in the future.

二维（2D）过渡金属二硫化碳（TMDC）单层是一类具有直接带隙和高激子结合能的超薄材料，为研究发光器件的光致发光（PL）提供了理想的平台。原子薄的TMDC通常包含各种缺陷，这些缺陷会丰富晶格结构并产生许多有趣的特性。由于缺陷的影响可能是有害的，也可能是有益的，因此，PL定制需要全面了解缺陷行为的内部机制。在此，总结并讨论了缺陷对PL发射的影响的最新进展。基本机理是本综述的重点，例如辐射/非辐射重组动力学和能带结构修饰。