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.