Full-visible-spectrum emission phosphors are promising candidates for next-generation white light-emitting diodes (WLEDs), overcoming the complex and high costs of traditional mixed phosphors. However, their practical application is hindered by low luminescence efficiency. In this regard, a generalization strategy is developed that involves creating heterostructure interfaces to prevent detrimental energy transfer processes, thereby boosting efficiency. The SrLiPO4/Sr9MgLi(PO4)7:Eu2+ single-grain phosphors prepared in this work have achieved remarkable full-visible-spectrum emission efficiency, with record internal and external quantum efficiencies of 76.1% and 56.2%, respectively. The WLEDs encapsulated with this phosphor feature a high color rendering index (approximate to 93.9), a low correlated color temperature (approximate to 3100 K), and stable color performance, indicating that the as-synthesized single-grain phosphors are excellent candidates for healthy full-visible-spectrum lighting. This innovation is expected to accelerate the development of full-visible-spectrum phosphors technology and inspires the creation of more efficient and versatile luminescent materials in the future.