Energy Transfer Probability Research Articles

Blue and white light emissions and energy transfer in Tm3+ and Dy3+/Tm3+ doped lithium-aluminum-zinc phosphate glasses

Lithium-aluminum-zinc phosphate glasses doped with thulium and dysprosium ions are characterized by using spectroscopy techniques. The Judd-Ofelt parameters were evaluated to calculate the radiative parameters of thulium 1D23F4 and 1G43H6 visible transitions and 3H43F4 near infrared transition, which shows the highest optical amplification parameters. Upon 356 nm excitation, the Tm3+ doped phosphate glass emits blue light with CIE1931 chromaticity coordinates x = 0.1540 and y = 0.0283 and color purity around 96.8%. With excitations at 347 and 350 nm, the Dy3+/Tm3+ doped phosphate glass emits neutral and cold white light with correlated color temperature values of 4716 and 6628 K, respectively. The dysprosium emission decay time in the codoped glass is shorter than that in the Dy3+ single-doped glass, indicating a non-radiative energy transfer from Dy3+ to Tm3+. The dominant electrical interaction involved in the energy transfer, following the model Inokuti-Hirayama, is of dipole-dipole type. The energy transfer probability and efficiency are 769.0 s-1 and 0.53, respectively. Tm3+ doped and Dy3+/Tm3+co-doped lithium-aluminum-zinc phosphate glasses could be appropriate for blue and neutral/cold white light-emitting device applications.

Tb3+ doped silicoborate glass scintillator for high resolution synchrotron X-rays imaging application

This research aims to develop a combination of SiO2 and B2O3 glass former (called, silicoborate glass) to be used as a scintillation material for digital radiography application. The silicoborate glass doped with different concentration of Tb2O3, xTb2O3–7.5Gd2O3–40Na2O–5SiO2– (47.5-x)B2O3, where x = 0, 1, 2, and 3 mol% (xTb:7.5Gd) were prepared by melting and then rapid quenching in graphite mold. The density of the prepared glasses was high with Tb2O3 concentration, indicating that the glass became denser and could strongly interact with X-rays. The molar volume increased with Tb2O3 concentration, suggesting the increase of Non-Bridging Oxygen (NBOs) in glass matrix. The xTb:7.5Gd glasses absorbed photons in visible and near-infrared regions and was observed that the absorption bands increased with Tb2O3 concentration, which was the result of the 4f6-4f6 transitions behavior of Tb3+ ions. The photoluminescence and radioluminescence results revealed the distinct emission occurring at 544 nm (5D4→7F5). The photoluminescence quantum yield (PLQY) of glass had the maximum efficiency at 30.85%. The luminescence peak area under X-rays excitation glass was maximum at 109% of BGO crystal. CIE 1931 chromaticity of the xTb:7.5Gd glasses showed the color coordinates in yellowish-green area. The decay time of the xTb:7.5Gd glasses were in the millisecond range for different excitations. The probability of energy transfer was investigated between Gd3+ and Tb3+ ions in glass and may occur mainly between the 6P7/2 level of Gd3+ and 5H7 level of Tb3+. The X-rays imaging using the developed glass as a scintillator was performed by Synchrotron X-rays and the spatial resolution 6 lp/mm was achieved. These results demonstrate that the 3 mol% of Tb2O3 doped silicoborate glass can be used as a scintillator and can be applied for a high-resolution Synchrotron X-rays imaging system.

Enhanced luminescence of Dy-activated in-situ synthesized LaAlO3/MgO nanocomposites for cool wLED and latent finger printing applications

In the current study, a series of trivalent Dysprosium doped La1-xDyxAlO3/MgO (with x = 0, 1, 3, 5, 7 and 9 mol. %) nanophosphor composites have been synthesized via Pechini sol-gel method. Structural properties were analyzed using XRD, Rietveld refinement and FESEM. The prepared nanophosphors exhibit rhombohedral/face-centered structure. The bandgap values of the nanophosphors were found to be in the range of 5.39–5.75eV. At the sintering temperature of 900 °C, La1-xDyxAlO3/MgO (x = 5 mol.%) nanocomposite exhibit significant enhancement in the white light emission as compared to La1-yDyyAlO3 (y = 5 mol.%). PL intensity of composite further increases with the rise in sintering temperature up to 1200 °C. Dexter's theory and Burshtein model when applied to PL and TRPL profiles unveil the d-d energy transfer mechanism that shifts from donor-acceptor to donor-donor transfer with dopant concentration. Other exemplary colorimetric and luminescence-based parameters such as, CRI, CCT, life-time, energy transfer efficiencies and probabilities indicate the potential suitability of fabricated phosphor for w-LED and imaging applications. The optimized nanophosphor composite, i.e., La1-xDyxAlO3/MgO (x = 5 mol.%) has been explored for Latent Finger Printing and it successfully identified all the levels-1, 2 and 3 features of fingerprint.

Supercollisions of NaCl + NaCl on an Accurate Full-Dimensional Potential Energy Surface.

An accurate, global, full-dimensional potential energy surface (PES) of NaCl + NaCl has been constructed by the fundamental invariant-neural network (FI-NN) fitting based on roughly 13,000 ab initio energies at the level of CCSD(T)-F12a/aug-cc-pVTZ, with the small fitting error of 0.16 meV. Extensive quasiclassical trajectory (QCT) calculations were performed on this PES to investigate the energy transfer process of the NaCl + NaCl collision at four different collision energies. Various quantities were obtained, including the cross-sections, energy transfer probability, average energy transfer, and collision lifetime. The probabilities of energy transfer (P(ΔE)) for prompt trajectories, nonreactive trajectories, and reactive trajectories deviate from a simple exponential decay pattern. Instead, a noteworthy probability is observed in the high-energy transfer region, indicative of supercollisions. The formation of the (NaCl)2 complex, coupled with a comparatively extended collision lifetime, promotes vibrational excitation in NaCl molecules. The reactive trajectories exhibit enhanced energy transfer, attributed to the longer lifetime of the NaCl dimer. This study not only provides an accurate and extensive understanding of the NaCl + NaCl collision dynamics but also reveals intriguing phenomena, such as supercollisions and enhanced energy transfer in reactive trajectories, shedding light on the complex intricacies of molecular interactions.

Thermal transport of graphene-C3B superlattices and van der Waals heterostructures: a molecular dynamics study

Two-dimensional (2D) materials have attracted more and more attention due to their excellent properties. In this work, we systematically explore the heat transport properties of Graphene-C3B (GRA-C3B) superlattices and van der Waals (vdW) heterostructures using molecular dynamics method. The effects of interface types and heat flow directions on the in-plane interfacial thermal resistance (ITRip) are analyzed. Obvious thermal rectification is detected in the more energy stable interface, GRA zigzag-C3B zigzag (ZZ) interface, which also has the minimum value of ITRip. The dependence of the superlattices thermal conductivity (k) of the ZZ interface on the period length (l p ) is investigated. The results show that when the l p is 3.5 nm, the k reaches a minimum value of 35.52 W m−1 K−1, indicating a transition stage from coherent phonon transport to incoherent phonon transport. Afterwards, the effects of system size, temperature, coupling strength and vacancy defect on the out-of-plane interfacial thermal resistance (ITRop) are evaluated. With the increase of temperature, coupling strength and vacancy defect, ITRop are found to reduce effectively due to the enhanced Umklapp phonon scattering and increased probability of energy transfer. Phonon density of states and phonon participation ratio is evaluated to reveal phonon behavior during heat transport. This work is expected to provide essential guidance for the thermal management of nanoelectronics based on 2D monolayer GRA and C3B.

Boosting Dye-Sensitized Luminescence by Enhanced Short-Range Triplet Energy Transfer.

Dye-sensitization can enhance lanthanide-based upconversion luminescence, but is hindered by interfacial energy transfer from organic dye to lanthanide ion Yb3+ . To overcome these limitations, modifying coordination sites on dye conjugated structures and minimizing the distance between fluorescence cores and Yb3+ in upconversion nanoparticles (UCNPs) are proposed. The specially designed near-infrared (NIR) dye, disulfo-indocyanine green (disulfo-ICG), acts as the antenna molecule and exhibits a 2413-fold increase in luminescence under 808nm excitation compared to UCNPs alone using 980nm irradiation. The significant improvement is attributed to the high energy transfer efficiency of 72.1% from disulfo-ICG to Yb3+ in UCNPs, with majority of energy originating from triplet state (T1 ) of disulfo-ICG. Shortening the distance between the dye and lanthanide ions increases the probability of energy transfer and strengthens the heavy atom effect, leading to enhanced T1 generation and improved dye-triplet sensitization upconversion. Importantly, this approach also applies to 730nm excitation Cy7-SO3 sensitization system, overcoming the spectral mismatch between Cy7 and Yb3+ and achieving a 52-fold enhancement in luminescence. Furthermore, the enhancement of upconversion at single particle level through dye-sensitization is demonstrated. This strategy expands the range of NIR dyes for sensitization and opens new avenues for highly efficient dye-sensitized upconversion systems.

An investigation about the ability to change color and the way energy is transferred of NaYMgWO6:RE3+ (RE3+ = Tm3+, Dy3+, Tm3+/Dy3+): A new type of single-phase white phosphor for WLEDs

Novel NaYMgWO6:Tm3+, Dy3+ phosphor is synthesized by solid-state reaction method in air. The phase structure was meticulously analyzed through XRD and Rietveld refinement techniques. Dy3+ doped NaYMgWO6 phosphors emitted yellowish-white light, which was observed. Surprisingly, the introduction of Tm3+ ions resulted in white-emitting, which was further studied with the aid of a spectrometer. By fixing the concentration of Tm3+ ions and subsequently adjusting the co-doping concentration of Dy3+ ions or altering the excitation wavelength, the CIE coordinates of NaYMgWO6:Dy3+, Tm3+ phosphors shifted from the blue-violet region to the yellowish-white region. In particular, when b = 0.2 mol, there was efficient energy transfer from Tm3+ to Dy3+, with an energy transfer efficiency of 95.1 %. The gradual decrease of the lifetime at 454 nm monitoring implies that there is indeed an energy transfer process from Tm3+ to Dy3+ and that the probability of energy transfer from Tm3+ to Dy3+ gradually increases with increasing Dy3+ concentration. These findings indicate that NaYMgWO6: aTm3+, bDy3+ phosphors offer a novel approach to researching single-phase white phosphors.

Visible and mid-infrared spectral features of Dy3+: SrF2 and Dy3+/Y3+: SrF2 crystals

In this work, Dy3+: SrF2 and Dy3+/Y3+: SrF2 crystals have been grown successfully by the Bridgman-Stockbarger method, and their absorption spectra, visible and mid-infrared (MIR) emission spectra, as well as fluorescence decay curves were analyzed. The advantages of co-doping Y3+ ions on the yellow and MIR emissions of Dy3+ ions were investigated. The intensity of yellow emission in the doubly-doped crystal is ∼ 4 times stronger than that of the singly-doped crystal. The absorption cross-section (0.782 × 10−21 cm2) at 452 nm and emission cross-section (1.156 × 10−21cm2) at 573 nm of Dy3+/Y3+: SrF2 crystal is higher than that of Dy3+: SrF2 crystal related values. Also, compared to Dy3+: SrF2 crystal, the emission cross-section (3.55 × 10−21 cm2) at 2880 nm and fluorescence decay time (1.062 ms) of Dy3+/Y3+: SrF2 crystal are found to be higher. When co-doped Y3+ ions, the distance between Dy3+ ions increased leading to the reduction of cross-relaxation and resonant energy transfer probabilities while enhancing the intensities of yellow and MIR emissions. From all the optical results, it can be inferred that Dy3+: SrF2 and Dy3+/Y3+: SrF2 crystals are potential materials to simultaneously realize yellow and MIR lasing action.

Preparation, structure and luminescent properties of P2O5–Gd2O3–Ga2O3–NaF–ZnO glasses co-doped with Tb3+ and Sm3+

White light-emitting diodes have been intensively explored as a technique of green energy-conversion in recent decades. In this work, a unique Tb3+/Sm3+ co-doped P2O5–Gd2O3–Ga2O3–NaF–ZnO glass consisting of Q0, Q1 and Q2 units was successfully synthesized. The DSC curves demonstrated that the glass stability gradually deteriorated with the increase of Sm3+ contents. The emission spectra exhibited the energy transfer from Dy3+ to Tb3+ ions, and the energy transfer efficiency and probability grew monotonously with the increase of Sm3+ contents. With the help of temperature-dependent emission spectra, the glasses were validated to be thermally stable. The fluorescence curves and Inokuti-Hirayama model demonstrated that the dominant mechanism in the energy transfer process was electric dipole-quadrupole interaction. In addition. the white-light emission with suitable chromaticity coordinates and CCTs could be obtained by adjusting the contents of the sensitizer and activator for PGGNZ glasses. All investigations revealed the potential application of Tb3+/Sm3+ co-doped glasses in optical device applications.

Exploring site-selective photoluminescence of Eu3+ and Tb3+ ions in Sr10(PO4)6F2 and the development of different phosphor materials

We have developed a wide range of phosphor materials with varying color characteristics in the green, yellow, orange, and red regions based on Sr10(PO4)6F2 matrix and different compositions of Eu3+ & Tb3+ ions. The site-selective Tb3+→Eu3+ energy-transfer dynamics found to play a great role for such tunable color characteristics. DFT based calculations were performed to understand the preference of lattice-site occupancy of the two dopant ions, which suggested that while Eu3+ ion prefers both Sr1 & Sr2 sites; Tb3+ only prefers Sr1 site. The site selective distribution has immediate impact on the photoluminescence lifetime values, wherein two different components were observed for both the dopant ions. In case of Eu3+ ion, the short-lived lifetime component of Eu3+ ion is originated when it is placed at Sr1 site and the long-lived component at Sr2 site, which has F-atom in its coordination and provides extra stability to the excited state at Sr2 site. However, for Tb3+ ion, the two lifetime components are explained based on the energy-transfer probability. The site-selective luminescence of Eu3+ & Tb3+ ions was found to play the key role while developing colour tuneable phosphor materials.

Comparison of the supercollisions of the deuterium atom with acetylene and ethylene

The collisions transferring large portions of the energy are often called supercollisions. By taking the D + C2H2 and D + C2H4 collision systems as examples, we investigate the difference between the two systems in the novel supercollision process at the collision energy of 70 kcal/mol. Based on the quasi-classical trajectory calculations, various quantities have been obtained and compared, including the energy-transfer probability P(ΔE), the average energy transfer <ΔE>, collision lifetime, and scattering angular distributions for the two systems, etc. It is found that although translationally hot D atom colliding with the acetylene can form the complex more probably than colliding with the ethylene, the latter can present an even higher efficiency for super energy transfer. This phenomenon can be understood by the fact that C2H4D complex has more degrees of freedom and a longer lifetime.

Description of nuclear fragmentation events induced by space radiation: An analytical approach

One of the features of the field of space radiation inside a spacecraft during an orbital flight is the presence of a secondary component in its composition. This component is generated in the environment due to nuclear interactions of primary radiation with the walls of the spacecraft, material load, biological objects, electronics, etc. Secondary radiation consists mainly of charged particles of a wide energy range and neutrons. The fluence of secondaries can be non-uniform, especially in the region adjacent to the vertex of the nuclear interaction. In this region, the local energy absorbed in matter can significantly exceed the volume average values. In this paper a calculation method is considered and the probability of large energy transfer in fragmentation events in the vicinity of the nuclear interaction vertex is estimated.

Effect of Solvent on Optical Properties and Surface Topography of Nanocomposite Conjugated Polymer Thin Film

The addition of TiO2 nanoparticles (NPs) to a white-emission conjugated polymer (CP) blend of poly(9,9-dioctylfluorene-2,7-diyl) (PFO) and poly(2-methoxy-5(2-ethylhexyl)−1,4-phenylenevinylene (MEH-PPV) enhanced the optical properties. However, the agglomeration of the nanoparticles restricted enhancement. This drawback was successfully overcome in this study. The highly polar solvent chloroform was mixed with toluene and used to prepare thin films of the blends. Solution blending and spin-coating techniques were used to prepare thin films with different TiO2 nanoparticle contents. In addition, pure toluene and chloroform were investigated as solvents for the nanocomposite blend. These three cases were compared by studying the emission spectra, absorption spectra, Commission Internationale d’Eclairage coordinates (CIE), field emission scanning electron microscopy (FE-SEM) images and scanning probe microscope (SPM) images. The average roughness, quenching constant, and energy transfer probability were calculated. The optimum physical properties of the thin film were achieved using nanoparticles at 15wt% and applied to the binary blend with a mixture of equal amounts of toluene and chloroform. Although chloroform is better for nanoparticle distribution, toluene is mandatory for obtaining the highest yield of PFO.

Single red upconversion luminescence in β-Ba2ScAlO5: Yb3+/Er3+ phosphor assisted by Ce3+ ions

Recent decades have witnessed an explosion in research devoted to pure upconversion (UC) red emission attractive for bioimaging and anti-counterfeiting. Single-band red UC emission of Er3+ has been implemented in the new β-Ba2ScAlO5: Yb3+/Er3+ phosphor assisted by Ce3+. The red to green integrated intensity ratio reaches up to 430.9. Doping of Ce3+ ions leads to large cross-relaxation probabilities between Er3+ and Ce3+ ions when excited at 980 nm near infrared laser, resulting in suppressing the green emission and enhancing the red emitting level of Er3+. The optimal doping concentration of Ce3+ ions is 0.008 in β-Ba2ScAlO5: Yb3+/Er3+ sample, and a 4.1-fold red emission intensity enhancement was achieved than that of β-Ba2ScAlO5: Yb3+/Er3+ sample without Ce3+ ions. The possible upconversion luminescence (UCL) mechanism is investigated according to absorption spectrum, excitation spectrum, photoluminescence spectrum and upconversion emission lifetime decay spectrum of Yb3+/Er3+/Ce3+ co-doped β-Ba2ScAlO5, which was concluded that the 5d-4f energy transfer and large cross-relaxation probabilities between Er3+ and Ce3+ ions to achieve enhancement of red emission and the super-high ratio of red to green UCL emission integrated intensity. This work can pave a perspective way to obtain new phosphor with single UC red emission for applications in a variety of the fields.

Heme Protein Binding of Sulfonamide Compounds: A Correlation Study by Spectroscopic, Calorimetric, and Computational Methods.

Protein–ligand interaction studies are useful to determine the molecular mechanism of the binding phenomenon, leading to the establishment of the structure–function relationship. Here, we report the binding of well-known antibiotic sulfonamide drugs (sulfamethazine, SMZ; and sulfadiazine, SDZ) with heme protein myoglobin (Mb) using spectroscopic, calorimetric, ζ potential, and computational methods. Formation of a 1:1 complex between the ligand and Mb through well-defined equilibrium was observed. The binding constants obtained between Mb and SMZ/SDZ drugs were on the order of 104 M–1. SMZ with two additional methyl (−CH3) substitutions has higher affinity than SDZ. Upon drug binding, a notable loss in the helicity (via circular dichroism) and perturbation of the three-dimensional (3D) protein structure (via infrared and synchronous fluorescence experiments) were observed. The binding also indicated the dominance of non-polyelectrolytic forces between the amino acid residues of the protein and the drugs. The ligand–protein binding distance signified high probability of energy transfer between them. Destabilization of the protein structure upon binding was evident from differential scanning calorimetry results and ζ potential analyses. Molecular docking presented the best probable binding sites of the drugs inside protein pockets. Thus, the present study explores the potential binding characteristics of two sulfonamide drugs (with different substitutions) with myoglobin, correlating the structural and energetic aspects.

Study on the interaction between nimodipine and five proteinases and the effects of naringin and vitamin C on these interactions by spectroscopic and molecular docking methods

The interaction mechanisms of nimodipine with pepsin, trypsin, α-chymotrypsin, lysozyme and human serum albumin were investigated by multispectral and molecular docking methods. Vitamin C and naringin were the main active components of grapefruit juice, and nimodipine was the typical drug that interacts with this juice. Fluorescence spectroscopy was used to study the interaction of nimodipine with five proteinases (pepsin, trypsin, α-chymotrypsin, lysozyme and human serum albumin) and the effects of vitamin C and naringin on these interactions. The fluorescence quenching results showed that nimodipine can quench the intrinsic fluorescence of these five proteinases by a static quenching procedure. Nimodipine binds to pepsin and α-chymotrypsin, through hydrogen bonding and van der Waals forces, whereas it binds to trypsin, lysozyme and human serum albumin mainly by hydrophobic interactions. The microenvironment of the five proteinases changed. The probability of nonradiative energy transfer between the five proteinases and nimodipine was high. Both vitamin C and naringin reduced the binding constant of nimodipine to the four proteinases (except α-chymotrypsin) and might increase the concentration of free nimodipine. Thus, vitamin C or naringin in fruits or foods could increase the blood concentration of free nimodipine and perhaps a reduction in nimodipine dose was needed.

Luminescence properties of Tb3+/Eu3+ co-doped glass based on GSBR system

In this work, a series of Tb3+/Eu3+ co-doped GeO2-SiO2-BaO-R2O3 (GSBR) glass were synthesized through high temperature melt cooling method. Luminescence properties of Tb3+/Eu3+ co-doped glass were studied by fluorescence spectrum, fluorescence lifetime and CIE coordinate. The energy transfer efficiency and probability were calculated by average donor distance and lifetime data, revealing that the type of energy transfer is the electric dipole-electric dipole interaction for Tb3+→Eu3+. And the efficiency of energy transfer from Tb3+ to Eu3+ increased greatly by increasing Eu3+ concentrations, which play an important role in adjusting the color at the excitation of 378 nm. The effects of different R2O3 (Gd2O3, Al2O3, Ga2O3) in the matrix on the luminescence intensity of the glass samples were compared. It was found that the luminescence intensity order of samples was Al2O3>Ga2O3>Gd2O3. Through the analysis of infrared and fluorescence spectra, the effects of different matrices components on the structure and luminescence properties of glass were revealed.

Enhanced red emission in Li2Mg3TiO6: Mn4+ phosphor via Na+ and Ge4+ doping

Li 2 Mg 3 TiO 6 : Mn 4+ /Na + /Ge 4+ phosphors with rock structure have been prepared via solid state reaction method. The phosphor has broad excitation band ranging from 265 nm to 600 nm with two peaks at 345 nm and 468 nm and can give strong red emission band peaking at 667 nm. The co-doped Na + /Ge 4+ ions largely improve the luminescence properties of Li 2 Mg 3 TiO 6 : Mn 4+ . It is found that the luminescence intensity of Li 2 Mg 3 TiO 6 : Mn 4+ /Na + /Ge 4+ is increased by 132% as compared with that of Li 2 Mg 3 TiO 6 : Mn 4+ phosphor. Meanwhile the quantum efficiency of Li 2 Mg 3 TiO 6 : Mn 4+ /Na + /Ge 4+ has also increased from 32.83% to 53.55%. The mechanism of luminescence improvement may be attributed to the lowered symmetry of [TiO 6 ] octahedral sites in Li 2 Mg 3 TiO 6 host induced by the doped Na + ions and the reduction of energy transfer probability among Mn 4+ ions caused by the doped Ge 4+ ions. The developed phosphor with suitable spectral properties has potential application in white-LEDs and plant growth. • Li 2 Mg 3 TiO 6 : Mn 4+ Quantum efficiency is increased by 20.7% due to Na + /Ge 4+ co-doping. • Spectra of the phosphor conforms to lighting and plant growth application. • Lowered Mn 4+ -site symmetry and reduced Mn 4+ -Mn 4+ pairs intensify Mn 4+ luminescence. • Multi-ion substitution strategy provides valid means for improving Mn 4+ emission.

Exploration of the Temperature Sensing Ability of La2MgTiO6:Er3+ Double Perovskites Using Thermally Coupled and Uncoupled Energy Levels.

This work aimed to explore the temperature-sensing performance of La2MgTiO6:Er3+ double perovskites based on thermally coupled and uncoupled energy levels. Furthermore, the crystal structure, chemical composition, and morphology of the samples were investigated by powder X-ray diffraction, energy-dispersive X-ray spectroscopy, and scanning electron microscopy, respectively. The most intense luminescence was observed for the sample doped with 5% Er3+. The temperature-dependent emission spectra of La2MgTiO6:5% Er3+ were investigated in the wide range of 77–398 K. The highest sensitivity of the sample was equal to 2.98%/K corresponding to the thermally coupled energy level 2H11/2 → 4I15/2 and 4S3/2 → 4I15/2 as compared to 1.9%/K, obtained for the uncoupled energy level 2H11/2 → 4I15/2 and 2H9/2 → 4I15/2. Furthermore, the 300 K luminescent decay profiles were analyzed using the Inokuti–Hirayama model. The energy transfer among Er3+ ions was mainly regulated by the dipole–dipole mechanism. The critical transfer distance R0, critical concentration C0, energy transfer parameter Cda, and energy transfer probability Wda were 9.81 Å, ions·cm−3, cm6·s−1, and 6020 s−1, respectively.

An Insight into the Effects of SnF2 Assisting the Performance of Lead-Free Perovskite of FASnI3: A First-Principles Calculations.

It is an effective method to use SnF2 and SnF4 molecules to assist in enhancing the performance of FASnI3 perovskite. However, the mechanism in this case is not clear as it lacks a certain explanation to specify the phenomenon. Through first-principles calculations, this paper constructed several modes of SnF2 and SnF4 adsorbed on the surfaces of FASnI3 and explored adsorption energies, band structures, photoelectric properties, absorption spectra, and dielectric functions. The SnF2 molecule adsorbed at the I5 position on the FAI-T surface has the lowest adsorption energy for the F atom, which is 0.5376 eV. The Sn–I bond and Sn–F bond mainly affect the photoelectric properties of FASnI3 perovskite solar cells, and the SnF2 adsorption on the FAI-T surface can effectively strengthen the bond energies, which shortens the bond lengths of the Sn–I and Sn–F bond, and eliminate surface unsaturated bonds to passivate the surface defects. Furthermore, the probability of energy transfer was lower between the SnF2 molecule and the ion around it than between SnF4 and its ion. Especially, in the aspect of optical properties, we found that the intensity of the absorption peak of SnF2 adsorption increase was larger than that of SnF4 adsorption. Additionally, the static dielectric constants of SnF4 adsorption on the two surfaces, denoted SnF4, made the perovskite respond more slowly to the external electric field. Based on this work, we found that SnF2 had a greater positive effect on the optical property of perovskite than SnF4. We consider that our results can help to deeply understand the essence of SnF2 assistance in the performance of FASnI3 and help researchers strive for lead-free perovskite solar cells.