Silicon-aluminum-oxigen (SiAlO) coatings doped with Sm²⁺ and prepared by reactive magnetron co-sputtering of Si, Al, and Sm targets, are attractive for luminescence solar concentrator applications but suffer from the low absorption between 300 and 600 nm. This article reports that the main cause of low absorption is a high concentration of undesired Sm³⁺. This finding is supported by optical transmittance, photoluminescence emission and excitation characterization, and X-ray photoelectron spectroscopy data of the Sm's 3d^5/2 edge. We present an alternative deposition process for obtaining Sm doped SiAlO layers with enhanced Sm²⁺ absorption by incorporating Sm through the use of multilayer thin-film precursors composed of metallic Sm and SiAlO layers. After thermal post-deposition treatments, diffusion and reaction of the metallic Sm layers with the SiAlO host results in coatings showing the characteristic 5d → 4f transitions of Sm²⁺ in the region between 250 and 600 nm which were not detectable in Sm-doped single layers. This same deposition strategy produces Tm doped SiAlO coatings with Tm²⁺‘s characteristic luminescence at 1132 nm when the SiAlO host is in the mullite composition region. The photoluminescence excitation spectrum of Tm²⁺ is compared to phosphor with similar composition and covers the range between 300 and 700 nm.

The commercial uptake of lithium-sulfur (Li-S) batteries is undermined by their rapid performance decay and short cycle life. These problems originate from the dissolution of lithium polysulfide in liquid electrolytes, causing charge and active material to shuttle between electrodes. The dynamics of intractable polysulfide migration at different length scales often tend to escape the probing ability of many analytical techniques. Spatial and temporal visualization of Li in Li-S electrodes and direct mechanistic understanding of how polysulfides are regulated across Li-S batteries starting from current collector and active layer coating to electrode-electrolyte interface are still lacking. To address this we employ neutron depth profiling across Li-S electrodes using the naturally occurring isotope, 6Li, which yields direct spatial information on Li-S electrochemistry. Using three types of Li-S electrodes, namely, carbon-sulfur, carbon-sulfur with 10% lithium titanium oxide (LTO), and carbon-sulfur with LTO membrane, we provide direct evidence for the migration, adsorption, and confinement of polysulfides in Li-S cells at work. Our findings further provide insights into the dynamics of polysulfide dissolution and re-utilization in relation to Li-S battery capacity and longevity to aid rational electrode designs toward high-energy, safe, and low-cost batteries.