ABSTRACT
The current pandemic crisis caused by SARS-CoV-2 has also pushed researchers to work on LEDs, especially in the range of 220-240 nm, for the purpose of disinfecting the environment, but the efficiency of such deep UV-LEDs is highly demanding for mass adoption. Over the last two decades, several research groups have worked out that the optical power of GaN-based LEDs significantly decreases during operation, and with the passage of time, many mechanisms responsible for the degradation of such devices start playing their roles. Only a few attempts, to explore the reliability of these LEDs, have been presented so far which provide very little information on the output power degradation of these LEDs with the passage of time. Therefore, the aim of this review is to summarize the degradation factors of AlGaN-based near UV-LEDs emitting in the range of 200-350 nm by means of combined optical and electrical characterization so that work groups may have an idea of the issues raised to date and to achieve a wavelength range needed for disinfecting the environment from SARS-CoV-2. The performance of devices submitted to different stress conditions has been reviewed for the reliability of AlGaN-based UV-LEDs based on the work of different research groups so far, according to our knowledge. In particular, we review: (1) fabrication strategies to improve the efficiency of UV-LEDs; (2) the intensity of variation under constant current stress for different durations; (3) creation of the defects that cause the degradation of LED performance; (4) effect of degradation on C-V characteristics of such LEDs; (5) I-V behavior variation under stress; (6) different structural schemes to enhance the reliability of LEDs; (7) reliability of LEDs ranging from 220-240 nm; and (8) degradation measurement strategies. Finally, concluding remarks for future research to enhance the reliability of near UV-LEDs is presented. This draft presents a comprehensive review for industry and academic research on the physical properties of an AlGaN near UV-LEDs that are affected by aging to help LED manufacturers and end users to construct and utilize such LEDs effectively and provide the community a better life standard.
ABSTRACT
Coronaviruses present a considerable concern for humans and animals. The current world- wide pandemic of SARS-CoV-2 virus showed many gaps in understanding of coronaviruses spread and transmission. Because of lack of effective vaccine against SARS-CoV-2 the only preventive measures are represented by wearing protective masks and gloves thus limiting potential risk of contact with the airborne virus. Inversely, the limited time of protective function of the masks presents another drawback of their use. Therefore, the application of disinfection agent dispersed on the surface of protective masks may enhance their effectivity and safety of their application. The aim of the study was to examine the virucidal efficacy of low-concentra- ted sodium hypochlorite dispersed using ultrasonic humidifier on the surface of surgery masks. The study was conducted using SARS-CoV-2 surrogate virus, namely porcine epidemic diarrhea virus (PEDV) representing a model with similar biophysical properties and genomic structure to human coronaviruses. Five different concentrations of the disinfectant with different content of sodium hypochlorite were selected for the study. A final concentration of 0.228 g/L sodium hypochlorite effectively inactivated the PED virus and may support the biosafety of masks usage.