Enhanced external luminescence quantum efficiency of ceramic phosphors by surface roughening

Ceramic phosphors show great promise for the realization of advanced high-power lighting devices. In the present work, ceramic Ce:YAG, which acts as a phosphor in white LEDs, was chosen as a case study to investigate the effect of surface roughness on the photoluminescence of ceramic phosphors. Highly transparent samples were fabricated by spark plasma sintering (SPS) and uniformly roughened with different grit size abrasive grinding paper. The average roughness (Ra) ranged from the nano-to the microscale (30-1570 nm). Photoluminescence (PL) emission intensity and external quantum efficiency (EQE) were found to significantly increase with surface roughness by 60 and 100%, respectively. Thus, we demonstrate a simple low-cost method to achieve a considerable increase in device brightness and efficiency.