Deep ultraviolet (DUV) light emitting diode (LED) at emission wavelength of 254 nm is inevitable to replace the conventional toxic mercury UV Lamp as demanded by Minamata Convention of 2020. Both the conventional DUV LEDs (C-LED) and tunnel junction (TJ)-based UVC LEDs are suffering from high operating voltages, low hole injection efficiency and efficiency droops. Therefore, p-AlGaN and n-AlGaN layers-based TJ is one of the most promising parts of optical devices and has been widely utilized as carrier tunneling in DUV LEDs to mitigate both the contact resistance for Ohmic contact and low hole injection efficicny at 254 nm emission. Here an approach is presented to electrically manipulate the quantum tunneling probability by exploiting the transported carriers at the interface of n-AlGaN/p-AlGaN TJ with moderate Si and Mg-doping levels and optimized thickness. As a result, the Augur recomination rate was sucesfully suppressed and quite high radiative recombination rates were achived in the 254nm TJ-based DUV LEDs, which is attributed the improved holes injection toward the MQWs when compared to C-LED. The internal-quantum efficiency (IQE) of approximately ~ 88% in the TJ-based LED with zero efficiency droop is achived, which is 1.3 times greater than the IQE of approximately ~ 66% in the C-LED with efficiency droop of 53%. Based on our known knowledge, this is the highest reported IQE (88%) at emission wavelength of 254 nm in the AlGaN TJ-based LED with efficiency droop of 0%. It was found that the light output powers (LOP) of TJ-LED increases linearly under the varying current density, whereas in the case of C-LED the LOP changes nonlinearly under varying current density. This is attributed to the lower Augure recombination rate in the MQWs of TJ-based DUV LED. The operating voltages were remarkable reduced from 20 V to 5.4 V under 200 mA operation, which is attributed to the thickness and doping optimization in TJ and better selection of realively lower Al-content in the contact-layer. The demonstrated TJ-based DUV LEDs opens the door to epitaxial growth of high-performance UV emitters in MOCVD and MBE for a plethora of biomedical applications.

We revisit the argument that link the efficiency of a solar cell to its reverse operation as a LED, in the case where the material is organic. In organic cells, exciton transport is an intermediate process between sunlight absorption and the generation of electric current. We show that quenching exciton radiation can be beneficial to cell efficiency, without contradicting the general rule prevailing for semiconductor cells. Our treatment allows us to discuss both bulk heterojunction and planar junctions.

In this paper, the overall performance of Cu-(In,Ga)-Se₂ (CIGSe) solar cells was improved in the ultraviolet (UV)–visible wavelength region by two-segment process. In which, adjusting DC sputtering powers (20–40 W) for absorbers (segment I), and metal-alloy compositions (CdS, ZnO/CdS, ZnMgO/CdS and ZnMgO) for buffers (segment II) were explored and characterized. Upon choosing the optimal-30-W CIGSe-absorber (with 0.95-CGI ratio) sputtered by the segment-I process, the Cu-rich film can distinctly boost grain growth, thus reducing the trap state density. After segment-II process as the toxic-CdS alternative, the optimal Zn_0.9Mg_0.1O-alloy buffer can reach the best conversion efficiency (η = 8.70%) was attained for the environmental protection. Meanwhile, and the overall internal/external quantum efficiencies (IQE/EQE) were improved by 13.15%, respectively for the 2.48–3.62-eV bandgap (short wavelength) range. The developed photovoltaic (PV) module (with 9 optimum-CIGSe cells) exhibits acceptable stability with a variance within ±5% over the 60-day experiment. This discovery in PV-device research contributes to a new scientific understanding of renewable energy. Furthermore, this study undeniably enhances the progress of practical applications for PV-modules in alignment with sustainable development goals. It also actively supports the development of eco-friendly communities.