The present invention describes photoluminescent apparatuses or colour filters (100a,100b,100c,100d) and methods (1000a,1000b) for manufacturing. A photoluminescent (PL) or quantum dot (QD) material (100) fills a pattern of trenches (40,42) formed on a surface or on opposite surfaces of an optically transparent substrate (20), being cured and sealed by an optically transparent cover (22); in another embodiment, the PL or QD material (100) are cured and sealed when two patterned optically substrates (20) are bonded together. Sealing of the PL or QD material in the trenches (40,42) preserves the optical and performance stability of these colour filters. These colour filters (100a, . . . 100d) are suitable for use in next generation UHD display screens or lighting applications.