Light Harvesting from Oxygen Vacancies and A- and B-Site Dopants in CaSnO₃ Perovskite through Efficient Photon Utilization and Local Site Engineering

Abstract

Significant research has been carried out in ABO 3 perovskites during last decades in tailoring their luminescence properties for advanced optoelectronics. However, research related to exploring contribution of defects, both cation and anion vacancies in photoluminescence for multicolor photon emission has never been explored. Here, in this work, we have harnessed the full gamut of light emission from violet-blue to deep red originating from oxygen vacancies (OVs) in undoped CaSnO 3 (CSO) and Eu@CaO 8 and Eu@SnO 6 sites in the doped CaSnO 3 :Eu 3+ (CSOE) perovskite. Any contribution of Sn 2+ and Eu 2+ , respectively, in photoluminescence of CSO and CSOE has been completely ruled out through Xray absorption near-edge structure. Synchrotron radiation-based extended Xray absorption fine structure and positron annihilation lifetime spectroscopy showed simultaneous distribution of Eu 3+ ions at both asymmetric CaO 8 and symmetric SnO 6 sites owing to a very high negative formation energy value of −6.56 eV for the same. By efficient photon utilization arising from two different charge transfer bands, axial oxygen of SnO 6 octahedra O1 → Eu 3+ CTB (∼250 nm) preferentially transfers energy to Eu@CaO 8 leading to intense electric dipole transition, whereas equatorial oxygen of SnO 6 octahedra O2 → Eu 3+ CTB (∼300 nm) excites Eu@SnO 6 leading to intense magnetic dipole transition. This analogy is confirmed by DFT, wherein it was found that the calculated energy difference between the valence band maxima and conduction band minima is 4.77 eV (∼250 nm) and 4.3 eV (∼300 nm) for Eu@Ca and Eu@Sn sites, respectively. This concept of site-selective excitation and local site engineering can be applied to a variety of optical materials, which provides a unique strategy for tuning other properties of multifunctional crystals that are highly sensitive to the dopant's local environment.

Thermally Stable Red‐Emitting Oxide Ceramics for Laser Lighting

“…This is evidence that oxygen vacancies are present and of their compensating role, in addition to being evidence of local disorder. [ 27 ]…”

“…This is evidence that oxygen vacancies are present and of their compensating role, in addition to being evidence of local disorder. [27] RIXS measurements (Figure 3b) were also performed to directly measure the important Eu 2+ 5d 1 to CB energy separations. Inelastic energy losses of 0.23 eV were observed for both STOE and SNOE.…”

Structural Changes from Conventional SrSnO3 to Ruddlesden–Popper Sr2SnO4 Perovskites and Its Implication on Photoluminescence and Optoelectronic Properties

“…Sample Preparation and Characterization. Sample preparation, characterization methods and instrumentation are the same as used in our earlier works 13 and hence has been only briefly described here. The samples were synthesized via a high temperature solid state method.…”

“…Structure–property correlation is one of the most fundamental aspects of material design that needs understanding at the molecular level for achieving excellence for designated applications. − Structure is a multivariate parlance, and it broadly covers several materials’ parameters such as defects, symmetry, distortions, and so forth. ,− Among multifunctional ceramics, the ABX 3 type perovskite is in the realm of scientific investigations owing to its interesting and unique optical, magnetic, catalytic, electrical, electronic, and dielectrics properties. − ,,,− SrSnO 3 in particular has been one of the most explored perovskites in achieving excellence in the area of luminescence, optoelectronics, ferroelectricity, and photocatalysis. − …”

Harvesting Light from BaHfO3/Eu3+ through Ultraviolet, X-ray, and Heat Stimulation: An Optically Multifunctional Perovskite

“…Materials designed with an objective to achieve superior optical properties require deep understanding of the defects, traps, radiation/structural stability, doping efficiency, dopant’s local structure, efficacy of host-to-dopant energy transfer, and so forth. − The set of objectives in making high quantum yield phosphor, which can have multifunctional applications, are specific to the need. On top of that, a material that can serve as a phosphor, scintillator, and thermoluminescent dosimeter would be a boon to the optical material scientific community as it will drastically reduce load on material engineers and designers. − …”