Group-III nitride compound semiconductors are regarded as the third-generation semiconductors for electronic and optoelectronic device applications.¹ 2. ^{– 3} The nitride alloys and their heterostructures offer the widest tunable bandgap, spanning from the ultraviolet (UV) ($\approx 6.2\mathrm{eV}$) to near-infrared ($\approx 0.7\mathrm{eV}$) spectrum.⁴ 5. ^{– 6} In particular, their ternary AlGaN and quaternary Al(In)GaN alloys are attractive candidates for UV device applications ranging between 6.2 eV (AlN) and 3.4 eV (GaN). There are a number of immediate applications, such as UV curing, medical diagnosis and sterilization, water/air purification, gas sensing, and surface inspections within this wavelength range.⁷ 8. 9. ^{– 10} Owing to the compactness and low-power consumption, AlGaN-based solid-state lighting systems are widely used in the UV-A (315 to 400 nm) and UV-B ranges (280 to 315 nm). A remarkable advantage of AlGaN UV devices is that they can replace conventional toxic and bulky mercury lamps covering the UV-C range (200 to 280 nm).

In this work, we report an easy, efficient method to synthesize high quality lithium-based upconversion nanoparticles (UCNPs) which combine two promising materials (UCNPs and lithium ions) known to enhance the photovoltaic performance of perovskite solar cells (PSCs). Incorporating the synthesized YLiF₄:Yb,Er nanoparticles into the mesoporous layer of the PSCs cells, at a certain doping level, demonstrated a higher power conversion efficiency (PCE) of 19%, additional photocurrent, and a better fill factor (FF) of 82% in comparison to undoped PSCs (PCE = ~16.5%; FF = 71%). The reported results open a new avenue toward efficient PSCs for renewable energy applications.

This study focuses on the preparation of $\mathrm{L}\mathrm{a}\mathrm{X}{\mathrm{O}}_3(\mathrm{X}=\mathrm{F}\mathrm{e},\mathrm{M}\mathrm{n},\mathrm{C}\mathrm{r},\mathrm{N}\mathrm{i})$ perovskite thin films using a simple set-up spin coating technique and the evaluation of their properties for application in switching memory devices. The properties of as-deposited films were thoroughly characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), UV-Vis spectroscopy, and a vibrating sample magnetometer (VSM). The results obtained revealed that the as-deposited films have a polycrystalline cubic structure. The film surfaces were uniform and densely packed without any voids, cracks, or pinholes. In addition, irregularly shaped grains were observed having an average size of $140$, $120$, $89$, and $70 \mathrm{n}\mathrm{m}$ for $\mathrm{L}\mathrm{a}\mathrm{F}\mathrm{e}{\mathrm{O}}_3$, $\mathrm{L}\mathrm{a}\mathrm{M}\mathrm{n}{\mathrm{O}}_3$, $\mathrm{L}\mathrm{a}\mathrm{C}\mathrm{r}{\mathrm{O}}_3$, and $\mathrm{L}\mathrm{a}\mathrm{N}\mathrm{i}{\mathrm{O}}_3$ films, respectively. VSM analysis demonstrated that $\mathrm{L}\mathrm{a}\mathrm{F}\mathrm{e}{\mathrm{O}}_3$ film exhibited superior magnetic properties compared to the other films. Furthermore, memory devices with $\mathrm{A}\mathrm{u}/\mathrm{L}\mathrm{a}\mathrm{X}{\mathrm{O}}_3(\mathrm{X}=\mathrm{F}\mathrm{e},\mathrm{M}\mathrm{n},\mathrm{C}\mathrm{r},\mathrm{N}\mathrm{i})/\mathrm{F}\mathrm{T}\mathrm{O}$ structures were fabricated, and their I-V characteristics were measured. In order to assess their performance, an endurance test was conducted. The findings indicated that $\mathrm{A}\mathrm{u}/\mathrm{L}\mathrm{a}\mathrm{F}\mathrm{e}{\mathrm{O}}_3/\mathrm{F}\mathrm{T}\mathrm{O}$ device exhibited higher $\raisebox{1ex}{$R_{HRS}$}\!\left/ \!\raisebox{-1ex}{$R_{LRS}$}\right.$ ratio ($~{7\times 10}^5$), low Set/Reset voltages, lower power consumption ($2.7\times {10}^{-4} \mathrm{W}$), and stable endurance with no significant degradation was observed in the LRS and HRS after 20 sweep cycles. These favorable parameters can be attributed to the reduced thickness, larger grain size, and excellent magnetic properties of the active-layer $\mathrm{L}\mathrm{a}\mathrm{F}\mathrm{e}{\mathrm{O}}_3$. Moreover, the conduction mechanism of the fabricated devices was investigated, revealing that the conduction in the LRS is primarily dominated by Ohmic behavior, while the HRS exhibited different conduction mechanisms.