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.

Two-dimensional (2D) materials have attracted great attention in optoelectronics because of their unique structure, optical and electrical properties. Designing high-performance photodetectors and implementing their applications are eager to promote the development of 2D materials. Position-sensitive detector (PSD) is an optical inspection device for the precise measurements of position, distance, angle, and other relevant physical variables. It is a widely used component in the fields of tracking, aerospace, nanorobotics, and so forth. Essentially, PSD is also a photodetector based on the lateral photovoltaic effect (LPE). This article reviews recent progress in high-performance PSD based on 2D materials. The high-sensitive photodetectors and LPE involved in 2D photodetectors are firstly discussed. Then, we introduce the research progress of PSD based on 2D materials and analyze the carrier dynamics in different device structures. Finally, we summarize the functionalities and applications of PSD based on 2D materials, and highlight the challenges and opportunities in this research area.