Realization of High Color Uniformity for Phosphor-Converted White Light-Emitting Diodes Through a Stamp-Printed Phosphor Coating

In this letter, we demonstrate a stamp-printed phosphor coating process to realize high angular color uniformity (ACU) for phosphor-converted white lightemitting diodes. In the proposed phosphor coatingmethod, the phosphor gel is printed on desirable areas, where it forms variable geometries through the transfer of the stamp bump. The phosphor coating method shows high flexibility in its fabrication of various phosphor layer geometries, including the frustum, inverted frustum, cube, and catenoid. ACU performances of different phosphor layer geometries weremeasured. The obtained results showthat the catenoid phosphor layer with the side inward width of 0.07 mm shows an excellent uniformangular correlated color temperature (CCT) distribution. Its maximum CCT variation is only 150 K at the viewing angles ranging from -80 degrees to 80 degrees when the averageCCT is approximately6300K. The analysisof the ACU performances of different phosphor layer geometries is presented.