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 light-emitting diodes. In the proposed phosphor coating method, 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 were measured. The obtained results show that the catenoid phosphor layer with the side inward width of 0.07 mm shows an excellent uniform angular correlated color temperature (CCT) distribution. Its maximum CCT variation is only 150 K at the viewing angles ranging from -80° to 80° when the average CCT is approximately 6300 K. The analysis of the ACU performances of different phosphor layer geometries is presented.