2D TiO2 photonic crystal-assisted Y3Al5O12:Ce ceramic-plate phosphor and free-standing red film phosphor for white LEDs

In this paper, the optical properties of a two-dimensional (2D) TiO₂ nanobowl photonic crystal layer (PCL)-assisted Y₃Al₅O₁₂:Ce (YAG:Ce) yellow ceramic-plate phosphor (CPP) and a free-standing K₂SiF₆:Mn (KSF:Mn) red film phosphor are introduced. By placing 2D TiO₂ PCL-assisted YAG:Ce CPP onto a blue emissive light-emitting diode (LED) cup, we achieved an increase in the luminous efficacy of 1.53 times compared to when flat YAG:Ce CPP was placed onto the cup. Despite the increased luminous efficacy, the low color rendering index (CRI) was maintained. In order to enhance the CRI, we applied various concentrations of free-standing KSF:Mn red film phosphor between 2D PCL-assisted YAG:Ce CPP or flat YAG:Ce CPP with a blue LED cup. The optical properties were measured by means of the electroluminescence (EL) by applying a constant current (350 mA) to the LED chip. As a result, we obtained a high CRI (91), a low correlated color temperature (CCT, 2580 K), and good luminous efficacy (75.0 lm/W) by applying free-standing red phosphor film with a concentration of 50 wt% to a 2D PCL-assisted YAG:Ce CPP-based LED.