Advanced approach for phosphor recovery and characterization of LED components

Abstract

This study introduces a novel approach for characterizing Light Emitting Diode (LED) devices by isolating their individual components—specifically the phosphor, housing, and LED chips—and analyzing each separately. Furthermore, we selectively recovered the phosphor embedded in the polydimethylsiloxane (PDMS) through a depolymerization reaction. Our study includes a diverse range of LED types, such as thirty distinct Surface-Mount Device (SMD) LEDs, Chip-on-Board (COB) LEDs, and filament LEDs, sourced from both commercial suppliers and discarded LED lamps. Metals within the phosphor materials and LED bodies were examined using an optical microscope, Scanning Electron Microscopy with Energy Dispersive X-ray Spectroscopy (SEM-EDX), and (Inductively Coupled Plasma – Atomic Emission Spectroscopy) ICP-AES. To access the phosphor, the PDMS layer covering the LED was degraded with a 0.5 M tetrabutylammonium fluoride in tetrahydrofuran (TBAF/THF) solution. Subsequently, the liberated phosphors and metallic bodies underwent leaching with aqua regia for analysis using ICP-AES. The analysis conducted on LED devices revealed the presence of Y, Sr, Eu, Lu, Ce, Al, Ga, Ca in the phosphor materials, and Au, Ag, Ni, Cu, and Fe in the metallic bodies, with Ti located in the housings. This comprehensive approach enabled the precise determination of the gravimetric composition of various LED components, including the phosphor, PDMS, metallic fractions, and housings.