Rational Defect Engineering via Calcium Doping for High-Efficiency Monolayer MoS2 Emission.

Two-dimensional transition metal dichalcogenides (TMDCs) hold great promise for next-generation optoelectronics. However, the low photoluminescence (PL) quantum yield due to inevitable defects during material preparation severely restricts their practical application. Here, we report a rational defect-engineering strategy based on first-principles calculations and realize it experimentally on MoS2 monolayers by doping with calcium atoms. First-principles calculations reveal that proper doping can introduce complementary defect levels to effectively tailor carrier dynamics. Guided by this theoretical design, we synthesized calcium-doped MoS2 monolayers via one-step chemical vapor deposition. The as-grown doped MoS2 flakes reach sub-millimeter scale (~568 μm). Compared with undoped samples, the Ca-doped MoS2 exhibits two orders of magnitude PL enhancement, significantly prolonged carrier lifetime, and efficient conversion from negative trions to neutral excitons. This strategy is also applicable to other alkaline earth dopants, providing a generalizable route for defect engineering in two-dimensional semiconductors.