Light quality shows strong effects on humans in many aspects, including aesthetics, psychology, physiology, and health. By assuming that natural light has the best light quality, devising a pseudo‐natural light is hence important and critical. Here, an all‐weather pseudo‐natural light is demonstrated based on a high number of broad‐band emitters. By doping six broad‐band organic light‐emitting dyes in three separate emission layers, for example, the light source can exhibit a 92–96% similarity with the sunlight from dawn to dusk, and a color gamut of 80% in terms of NTSC. By combining six narrow‐band light‐emitting diodes (LEDs), a much wider gamut of 121% NTSC is achievable, but with a slightly poor daylight similarity, i.e., ranging between 80% and 83%. The daylight similarity, however, can easily be enhanced to at least 94% upon incorporating broad‐band phosphors, even with the use of only one or two LEDs.

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Plant factories have attracted increasing attention because they can produce fresh fruits and vegetables free from pesticides in all weather. However, the emission spectra from current light sources significantly mismatch the spectra absorbed by plants. We demonstrate a concept of using multiple broad-band as well as narrow-band solid-state lighting technologies to design plant-growth light sources. Take an organic light-emitting diode (OLED), for example; the resulting light source shows an 84% resemblance with the photosynthetic action spectrum as a twin-peak blue dye and a diffused mono-peak red dye are employed. This OLED can also show a greater than 90% resemblance as an additional deeper red emitter is added. For a typical LED, the resemblance can be improved to 91% if two additional blue and red LEDs are incorporated. The approach may facilitate either an ideal use of the energy applied for plant growth and/or the design of better light sources for growing different plants.

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