Selecting Morphology of Y₃Al₅O₁₂:Ce³⁺Phosphors for Minimizing Scattering Loss in the pc-LED Package

This paper reports the conversion efficiency (CE) and packaging efficiency (PE) of white phosphor-converted light-emitting diodes (pc-LED) with four morphologically different phosphors, such as nanophosphors (NPs), thin-film phosphors (TFPs), ceramic plate phosphors (CPPs), or micro-size powder phosphors (MPPs) to search for additional room for minimizing the scattering loss of conventional MPPs used in a conventional white pc-LED. The newly developed film-type phosphors with optical structures employ a two dimensional photonic crystal layer (2D PCL) to improve the extraction efficiency as well as optical short-wave pass filters (SWPFs) for recycling of backward emission loss. A careful evaluation of the CE, PE and internal quantum efficiency (IQE) shows that the 2D PCL, SWPF-assisted NP thick films characteristics and 2D PCL-assisted CPP characteristics, such as an improved PE and reduced scattering loss, satisfy the requirements for current white pc-LED applications. Therefore, a 2D PCL-assisted CPP-capped pc-LED shows a CE of ∼56% and a PE of ∼70%, surpassing the values (∼55, ∼63%) observed in the typical MPP-based white pc-LED at 350 mA. In addition, a 2D PCL, SWPF-assisted NP thick film-capped LED shows a CE of ∼31% and PE of ∼82%, indicating that there is a large room for further improvement in the IQE of as-prepared NPs.