Recent Advances in Packaging Technologies of AlGaN‐Based Deep Ultraviolet Light‐Emitting Diodes

Abstract

AlGaN‐based deep ultraviolet light‐emitting diodes (UV LEDs) have gained rapidly growing attention due to their wide applications in water purification, air disinfection, and sensing as well as optical communication. Moreover, deep UV radiation has been verified as one of effective way to inactivate COVID‐19. However, although numerous efforts have been made in deep UV LED chips, the reported highest external quantum efficiency (EQE) of them is 20.3%, which is far lower than that of visible LEDs. The EQE of commercial packaged AlGaN‐based deep UV LEDs is usually lower than 5%, which will cause serious reliability problems as well. Therefore, it is very urgent to improve EQE and reliability of the devices from packaging level. In this review, a systematical summarization about the packaging technologies of AlGaN‐based deep UV LEDs has been analyzed and future prospects have been made as well. Firstly, this work provides a brief overview of the devices and analyzes why the packaging level reduces EQE and reliability in theory. Then, systematically reviews the recent advances in packaging technologies and deep UV micro‐LEDs. Finally, conclusions and outlooks are given as well. This review is of great significance for promoting the development of the packaging technologies for AlGaN‐based deep UV LEDs.

Chromaticity-Tunable All-Inorganic Color Converters Fabricated by 3D Printing for Modular Plant Growth Lighting Devices

“…Natural light is seriously affected by the alternation of day and night, seasons, latitude, and weather conditions. , The regulation of artificial light has become an inevitable choice for improving the efficiency of agricultural production according to the rhythm of the growth and development of plants . At present, light-emitting diodes (LEDs) have become a new generation of lighting sources that are suitable for modern intelligent agricultural production due to their high brightness, energy efficiency, environmental protection, low voltage, adjustable wavelength, etc. − However, as a result of the poor chemical stability and thermal conductivity of the organic encapsulation resin in commercial LEDs, the aging and yellowing of resin and the degradation of the performance of the phosphor easily occur under long-term irradiation of high-power chips or in a high-temperature environment, resulting in light failure, color deviation, and short actual service lives of LEDs. In addition, the narrow emission bandwidth of commercial plant lighting LEDs cannot meet the requirements of the growth and development rhythms for different plants.…”

Synthesis and characterization of a new rare earth borate nonlinear optical crystal K7PbLu2B15O30

“…Nonlinear optical (NLO) materials have an important role in lithography, semiconductor manufacturing, and laser technology. [1][2][3][4][5][6][7][8] Over the past few decades, with continuous efforts, scientists have developed many commercially available NLO materials for application in the ultraviolet to mid-infrared regions, for example BaB 2 O 4 (BBO), 9 LiB 3 O 5 (LBO), 10 KH 2 PO 4 (KDP), 11 KTiOPO 4 (KTP), 12 AgGaQ 2 (Q = S, Se), 13,14 ZnGeP 2 (ZGP), 15 LiGaS 2 , 16 LiInSe 2 , 17 and GaSe. 18 In general, the following specifications must also be satisfied for a NLO crystal with suitable performance: 19 a non-centrosymmetric space group to perform the NLO function, an enough effective NLO coefficient (d eff > 0.39 pm V −1 ), a wide band gap (E g > 6.2 eV) and an acceptable birefringence (0.05-0.1) to achieve phase matching.…”

A considerable improvement of long-persistent luminescence in LiLuSiO4:Pr3+ phosphors by Sm3+ co-doping for optical tagging applications

“…12,13 The newly developed solid-state deep UV lightemitting diodes (LEDs) are able to overcome the shortcomings of gaseous lamps in some aspects, but the requirements of a complex preparation process, high production cost, and low external quantum efficiency of these AlGaN-based deep UV LED chips are still unsolved issues. 14,15 In recent years, light converter technology has also been explored as a cost-effective and alternative approach to designing solid-state deep UV light sources by combining luminescent materials such as lanthanide-doped upconversion phosphors and carbon dots with a LED chip or a laser diode. [16][17][18][19] Nevertheless, low deep UV output power and inadequate conversion efficiency still haunt their practical applications.…”