- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
First-principles calculations of optoelectronic properties of CaO: Eu+2 (SrO: Eu+2) for energy applications
摘要： We have performed the first-principles density functional theory (DFT) and DFT+U calculations on the electronic and optical properties of CaO: Eu+2 (SrO: Eu+2) phosphors compounds. Herein, we have focused on the polarization of the electronic structures, i.e., the energy bandgap and the density of states. All electrons were treated within the most common exchange and correlation functional called generalized gradient approximation plus optimized effective Hubbard parameter U as GGA+U. GGA+U is a very effective tool for describing the electronic band energy upto considerable accuracy. Hence, we have opted for the arbitrary values of U as 3.0, 4.0, 5.0 and 7.0 eV to treat the strongly correlated electrons for obtaining the matching result with the experimental one. However, GGA+U is highly expensive in terms of computation due to interaction of d or f electrons. The result shows that the appearance of Eu-4f states at the valance band maximum of the spin-up causes a substantial impact on the electronic properties of the studied compounds. The value of energy bandgap is smaller in case of spin up as compared to spin down case. In case of majority spin, the energy gap of 2.224 (2.14) eV belongs to the Eu-4f orbitals and governs the CBM. The partial densities of states (PDOS) structure displays a strong hybridization that may be pointed to the formation of covalent bonds. The calculated and the measured values are in good agreement with each other. In the study of optical properties of the compound, the optical spectral structure shows a lossless region and uniaxial anisotropy. The value of uniaxial anisotropy is positive at static limit and its value is negative above this value.
关键词： DFT,optical properties,Polymorph phosphor,bandgap,LEDs
更新于2025-09-04 15:30:14
-
Omnidirectional optogenetic stimulation
摘要： Omnidirectional optogenetic stimulation. A wireless, low-power optoelectronic platform, which is based on micro-LEDs, can provide multimodal programmable control over optogenetic stimulation parameters. Optogenetics is a powerful tool for perturbing populations of specific cell types. Here, individual cell types of the central and peripheral nervous systems are tagged with light-sensitive opsins. Specific wavelengths of light can then be used to turn the cells off and on, allowing complex neural circuitry to be dissected. For example, blue light can be used to activate neurons and green light can be used to deactivate neurons depending on the expression of either channelrhodopsin-2 (ChR) or halorhodopsins (Halo), respectively. The technique has been important in elucidating new neural pathways in many preclinical models of disease (including those related to memory, depression, sleep, anxiety, and restoration of vision) and could lead to potential new disease targets.
关键词： wireless,micro-LEDs,optogenetics,disease models,neural circuitry
更新于2025-09-04 15:30:14
-
Phosphomolybdic acid as an efficient hole injection material in perovskite optoelectronic devices
摘要： Efficient perovskite devices consist of a perovskite film sandwiched between charge selective layers, in order to avoid non-radiative recombination. A common metal oxide used as a p-type or hole transport layer is molybdenum oxide. MoO3 is of particular interest for its very large work function, which allows it to be used both as an interfacial charge transfer material and a dopant for organic semiconductors. However, high quality and high work function MoO3 is typically thermally evaporated in a vacuum. An alternative solution-processable high work function material is phosphomolybdic acid (PMA), which is stable, commercially available and environmentally friendly. In this Communication, we show the first application of PMA in efficient vacuum processed perovskite devices. We found that the direct growth of perovskite films onto PMA leads to strong charge carrier recombination, hindering the solar cell photovoltage. Using an energetically suitable selective transport layer placed between PMA and the perovskite film, solar cells with efficiency >13% as well as LEDs with promising quantum efficiency can be obtained.
关键词： LEDs,optoelectronic devices,perovskite,hole injection material,phosphomolybdic acid,solar cells
更新于2025-09-04 15:30:14
-
X-ray study of anisotropically shaped metal halide perovskite nanoparticles in tubular pores
摘要： Recently, we have reported that metal halide perovskite nanoparticles formed in nanoporous alumina and silicon thin films exhibit blue shifted photoluminescence due to spatial confinement, thus allowing for color tuning of the emission by varying the pore size. While perovskite nanoparticles grown in nanoporous alumina films have been integrated into LEDs, similar approaches have failed with silicon. Here, we report the results of investigating the structure of the alumina pore system and the perovskite crystallites forming within. We use two x-ray diffraction techniques, namely, small-angle x-ray scattering (SAXS) and high-energy microbeam wide-angle x-ray scattering (WAXS). SAXS reveals that the alumina pore system diffracts like regularly arranged tubes with the average diameter and nearest neighbor distance of 12 nm and 20 nm, respectively. High-energy microbeam WAXS shows that perovskite nanoparticles within the nanoporous alumina have a distinctly anisotropic shape with the average particle length along and perpendicular to the pore axis of 26 nm and 13 nm, respectively. In contrast, no shape anisotropy has been detected for nanoparticles inside the silicon pores in a previous study. This suggests that utilizing nanoporous alumina has a twofold advantage. First, the tubular alumina pores, spanning the entire insulating film, offer percolated paths for the perovskite to fill. Second, the elongation of the nanoparticles in the tubular alumina pores can be expected to aid device performance as the length of the nanoparticles approaches the active layer thickness (ca. 40 nm) of LEDs, while the small diameter of the crystallites accounts for the observed blue shifted emission.
关键词： LEDs,anisotropic shape,nanoporous alumina,SAXS,WAXS,nanoparticles,metal halide perovskite
更新于2025-09-04 15:30:14