An illumination module includes a light mixing cavity with an interior surface area and window that are physically separated from an LED. A portion of the window is coated with a first wavelength converting material and a portion of the interior surface area is coated with a second wavelength converting material. The window may be coated with LuAG:Ce. The window may also be coated with a third wavelength converting material with a peak emission wavelength between 615-655 nm where the spectral response of light emitted from the window is within 20% of a blackbody radiator at the same CCT. The LED may emit a light that is converted by the light mixing cavity with a color conversion efficiency ratio greater than 130 lm/W where the light mixing cavity includes two photo-luminescent materials with a peak emission wavelengths between 508-528 nm and 615-655 nm.