Excited-State Energy Manipulation Enables Single-Layer White Light-Emitting Diodes to Simulate the Solar Spectrum

White light-emitting diodes (WLEDs) have been widely researched and applied for their characteristics of energy savings and environmentally friendliness. However, the spectrum of WLEDs is quite different from that of natural sunlight, and long-term use can have an impact on both physiological and psychological health. Three strategies have been designed to address the issue of spectral defects by revealing the exciton energy transfer and distribution behavior between multiple excited states. Here, single emitting layer (SEL)-WLEDs are designed to simulate the solar spectrum, which exhibits excellent spectral stability at different operating voltages, demonstrating that exciton distribution can maintain dynamic balance. In addition, these devices can accurately replicate sunlight during different time periods, with a high color rendering index (CRI ∼ 90) and a nearly 90% coverage in the human comfort region. Meanwhile, the ultraviolet, deep blue, and near-infrared regions were reduced by 100%, 80%, and 90%, respectively. These results indicate that the strategies are expected to be used to promote the physical and mental health of those who work in environments far from natural light for a long time.