This paper reports an AlGaN-based narrow-band ultraviolet-B (NB-UVB) light-emitting diode (LED) exhibiting a single electroluminescence peak with a full-width at half-maximum (FWHM) of less than 10 nm at forward currents (I f ) from 10 to 200 mA, broadening to 11.6 nm when the forward current reached 350 mA. We attribute the narrow FWHM to effectively decreasing the degrees of piezoelectric polarization in the MQWs, and the excess electron overflow from the MQW to the p-layer was avoided. The maximum external quantum efficiency (EQE) of 2.16% and wall plug efficiency of 1.74% occurred when the forward current was 10 mA; the EQE dropped by 8.6% when the forward current increased from 10 to 60 mA. Furthermore, the light output power decreased to 85.4 and 82.5% of its initial value after 620 and 3500 h, respectively, under conditions of 60 mA dc aging. The characteristics of this NB-UVB LED suggest great potential for its application in phototherapy.
This paper elucidates the increased luminescence efficiency of CsPbBr2.1Cl0.9 sky-blue perovskite light-emitting diodes (PeLEDs) achieved through the interface modification of 3,4 ethylenedioxythiophene (PEDOT):polystyrene sulfonic acid (PSS)/quasi-two-dimensional (QTD) perovskite using CsCl and CsBr materials, respectively. QTD films were fabricated using ratios of CsPbBr2.1Cl0.9 doped with phenethylamine hydrobromide (PEABr) at 60%, 80%, and 100%. The solvent dimethyl sulfide (C2H6OS) was employed under the excitation of ambient and 365-nm laser lights. The PeLED structure was composed of Al/LiF/2,2',2"-(1,3,5-benzinetriyl)-tris(1-phenyl-1-H-benzimidazole) (TPBi)/CsPbBr2.1Cl0.9:PEABr/interface modification layer/PEDOT:PSS/ITO glass. The optimized results revealed that the luminance, current efficiency, and external quantum efficiency of the QTD CsPbBr2.1Cl0.9:80% PEABr PeLED with the CsCl interface modification additive was 892 cd/m2, 3.87 cd/A, and 5.56%, respectively.
In this paper we report epoxy molding compound lead frames (EMC-LFs) with encapsulated silicone as a simple and inexpensive packaging for AlGaN-based ultraviolet-B (UVB) light-emitting diodes (LEDs) displaying high light extracting efficiencies (LEE) and long operation lifetimes. The convex surfaces and beveled shapes obtained after curing the encapsulated silicone surrounding the UVB-LED chips significantly enhanced the light output power (LOP). With silicone present inside the EMC-LFs having bonding cavity diameters of 1.7 and 1.45 mm, the LOPs of the UVB-LEDs improved by 26 and 42%, respectively; reliability tests performed over a period of 1000 h revealed, however, that the LOPs decreased to 70 and 71%, respectively, of their initial values, but no cracks appeared in the silicone during such longterm operation. Thus, the stability of silicone-encapsulating EMC-LFs for UVB-LEDs was acceptable. When compared with AlN-based direct plating copper ceramic lead frames (AlN-DPC-LFs), our proposed packaging structure and method have the potential to lower the manufacturing cost of UVB-LEDs.INDEX TERMS AlGaN, AlGaN-based ultraviolet-B LEDs, Packaging, Light output power.
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