Abstract: A wavelength converting structure is provided. The wavelength converting structure comprises the following: a substrate, and a wavelength converting coating which is deposited on the substrate and comprises: (a) a phosphor powder which can be excited by UVC; and (b) an anti-UVC adhesive, wherein the thickness of the wavelength converting coating is 2 to 10 times the average particle size of the phosphor powder and the amount of the phosphor powder in the wavelength converting coating conforms to at least one of the following requirements: (i) the phosphor powder should be about 30% to 85% by volume of the wavelength converting coating based on the total volume of the phosphor powder and the adhesive; and (ii) the weight ratio of the phosphor powder to the adhesive should range from 1:1 to 20:1. The wavelength converting coating can effectively convert UVC to visible light to provide a visible light source with a high surface area.