A stack of layers 100, a lamp, a luminaire and a method of manufacturing a stack of layers is disclosed. The stack of layers 100 comprises a first outer layer 102, a second outer layer 106 and a luminescent layer 104. The first outer layer 102 and the second outer layer 106 are of a light transmitting polymeric material and have an oxygen transmission rate lower than 30 cm3/(m2-day) measured under standard temperature and pressure (STP). The luminescent layer 104 is sandwiched between the first outer layer 102 and the second outer layer 106 and comprises a light transmitting matrix polymer and a luminescent material 108 being configured to absorb light according to an absorption spectrum and convert a portion of the absorbed light towards light of a light emission spectrum.