A light emitting device comprises: a thermally conductive substrate (MCPCB); at least one LED mounted in thermal communication with a surface of the substrate; a housing attached to the substrate and configured such the housing and substrate together define a volume that totally encloses the at least one LED, the housing comprising at least a part that is light transmissive (window); and at least one phosphor material provided on an inner surface of the housing within said volume said phosphor being operable to absorb at least a part of the excitation light emitted by the at least one light emitting diode and to emit light of a second wavelength range. The housing is attached to the substrate such that the volume is substantially water tight, preferably air/gas tight.