Plant habitat-conscious white light-emitting devices: Dy3+-emission considerably reduces involvement in photosynthesis†
Outdoor white lighting systems may destroy natural plant habitats, particularly in dark sites, by allowing other species to thrive due to the increase in illumination intensity. Therefore, lighting that does not affect plant growth is required. In this work, we prepared a Dy-phosphor, K2Y1−xDyx(WO4)(PO4) (KYWP:Dy), that exhibited a pale yellow-white luminescence consisting of sharp emission peaks derived from the Dy3+ luminescence. A bright white light-emitting device (WLED) was fabricated from a near-UV LED (385 nm) and the KYWP:Dy phosphor (Dy-WLED). Its CIE color coordinates and correlated color temperature were CIE(0.357, 0.374) and 4670 K, respectively. The plant cultivation tests using Chlorella dispersions were carried out by using the Dy-WLED and conventional WLEDs. The Chlorella growth under the Dy-WLED illumination was suppressed to only 26% that of the samples under conventional WLED illumination. This was achieved by reducing the similarity of the emitted light to the photosynthetic action spectrum and red-near-IR emission, which suppressed photosynthesis. Thus, we expect that our Dy-WLED is promising for creating WLEDs that preserve natural plant habitats.