A light emitting device comprises: an excitation source (LED) operable to generate excitation light of a first wavelength range and a phosphor (photo-luminescent) material configured to absorb at least a part of the excitation radiation and to emit light of a second wavelength range. Light emitted by the device comprises the combined light of the first and second wavelength ranges. The device is characterized by at least the light emitting surface of the excitation source being coated (encapsulated) with an encapsulating material which is transparent to light of the first and second wavelength ranges and which incorporates particles of a thermally conducting material (thermal conductivity ≧100 Wm−1K−1, e.g. silver, aluminum or carbon nano-particles) distributed throughout its volume. The phosphor material can be provided on a surface of the encapsulating material, incorporated in the encapsulating material and/or applied to the surface of, or incorporated, in an optical component such as a lens.