This application discloses a new family of inorganic-organic hybrid semiconductor bulk materials built on periodic nanostructured 2D layers of ZnS that emit bright white light with high quantum efficiency. These ZnS-based crystalline inorganic-organic hybrid semiconductors have well defined and precisely controllable crystal structure and composition. Their optical emission properties, including intensity, quantum yield, and color quality, can be systematically tuned by varying the composition of both inorganic and organic components. Methods for preparing these materials, use of these materials as a new type of single-phased white light emitting phosphors, and their applications in making WLED devices are also disclosed.