High-Performance White Light-Emitting Diodes With Stable 3-D-Printed Lead-Free Perovskite Color Conversion Layers

This work demonstrates the fabrication and characteristics of white light-emitting diodes (WLEDs) using 3-D-printed lead-free perovskite color conversion layers (CCLs). The fabricated WLEDs consist of an ultraviolet (UV) LED chip array and three CCLs: yellow-emitting double perovskites, green-emitting Cu-based perovskites, and a blue-emitting photon downconverter (DC). Liquid crystal display (LCD)-based 3-D-printing technique was employed to encapsulate lead-free photon DCs into three thin resin-based layers, respectively. The WLED devices show excellent optical performance with luminous efficacy of radiation (LER) up to 260 lm/W, color rendering index (CRI) up to 97, tunable correlated color temperature (CCT) from warm white light, neutral white light (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${x} =0.32$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${y} =0.33$ </tex-math></inline-formula>) to cold white light, tunable circadian action factor (CAF), and extremely small delta uv (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${D} _{\text {uv}}$ </tex-math></inline-formula>). On the other hand, the daily measurement of photoluminescence quantum yield (PLQY) shows good stability of the printed CCLs, which proves encapsulating perovskites in transparent resin by 3-D-printing technique is effective in protecting perovskite from degradation. These experimental results confirm the validity of fabricating WLEDs using the 3-D-printing method to form anti-degradation perovskite-resin CCLs.