An area of considerable research interest is the development of visible light, down- conversion phosphors for application in white light emitting diodes (LEDs). In such devices, a blue LED can act as the primary light source, exciting photoluminescence in a phosphor with subsequent broad band emission occurring at visible wavelengths of lower energy. A combinatorial approach to synthesize and screen potential inorganic phosphors for such an application has been developed. Using solution chemistry techniques, solid state thin film arrays of (Y1−xGdx)3-z(Al1−yGay)5O12:Ce3+
Z, where x and y range from 0 to 1.0 and z is equal to 0.03 were synthesized. Subsequent characterization demonstrates that the combinatorial approach can be used to rapidly screen potential phosphors for use as luminescence down-converters in white LEDs. Emission and excitation trends match those reported in the literature for traditionally prepared powder samples. The optimal Ce3+ concentration in Y3Al5O12 (YAG) was identified as approximately 1.5 mol%, and within the YAG-substituted host specific compositions were identified as promising blue to yellow phosphor candidates.