Method for dyeing a layer of a nanocrystalline material on a substrate using a liquid dye, comprising the successive steps of (i) providing said layer on a substrate, (ii) providing an apparatus for dyeing said layer, which apparatus comprises at least a supply container for the liquid dye, a closable substrate holder provided with at least one inlet and at least one outlet for a substrate provided with a layer of nanocrystalline material, and conduit and circulation means for causing the liquid dye to circulate through the supply container and the substrate holder, (iii) placing the substrate with said layer in the substrate holder and closing the substrate holder, and providing a liquid dye in the supply container, and (iv) causing the liquid dye from the supply container to circulate for a determined time through the substrate holder, and apparatus for performing this method.