Divalent cations mixed lead halide perovskites with enhanced performances, high stabilities, and reduced toxicity are requisite to make persistent progress in perovskite solar cells. However, the mixing strategy is not reported extensively in search of a lead reduced structure. Herein, we report the structural, electronic and optical properties of RbPb{1-x}MxI3 (where, M={Sn,Ge} and x={0.25, 0.50, 0.75}) by alloying the B-site with Sn and Ge, using the density functional theory. The formation enthalpy is estimated for all RbPb{1-x}MxI3 (with x= 0.25, 0.50, 0.75), which confirms stability for all the structures. The energy bandgap and density of states (DOS) have been thoroughly investigated. The energy bandgap decreases with the increasing Sn/Ge contents, the lowest bandgap of 1.850 eV is observed at x = 0.50 in the case of RbPb{1-x}GexI3 systems. Further, the effective masses and the binding energy of excitons and spectroscopic limited maximum efficiency (SLME) are also estimated for all the mixed systems. The exciton type is observed to change from Mott-Wannier to Frenkel type with increasing the contents of both Sn and Ge at the B-site. The maximum efficiency of 23% is achieved using an active layer containing an equal admixture of Sn/Ge and Pb. The estimated parameters of both the mixed systems are consistent with the available literature of similar types.
Dispersion corrected density functional theory ($ω$B97X-D DFT) method is used to study the molecular hydrogen adsorption in $Ni_nMg_m$ $(1\geq n\geq 3,1\geq m\geq9)$ clusters. All these clusters can effectively adsorb multiple $H_2$ in the preferred binding energy (BE) range between physisorption and chemisorption, i.e., $0.1 eV\geq BE \geq0.8 $eV. $H_2$ adsorption on $Ni_kMg_k$ (Ni:Mg=1:1), $Ni_kMg_{2k}$ (Ni:Mg=1:2) and $Ni_kMg_{3k}$ (Ni:Mg=1:3) (k=1-3) clusters shows fascinating behaviours in terms of Ni:Mg alloying ratio and cluster size. In each Ni:Mg ratio, the number of adsorbed $H_2$ in…
The miscibility of Au and Li exhibits a potential application as an adhesion layer and electrode material in secondary batteries. Here, to explore alloying properties, we constructed a neural network potential (NNP) of Au-Li binary systems based on density functional theory (DFT) calculations. To accelerate construction of NNPs, we proposed an efficient and inexpensive method of structural dataset generation. The predictions by the constructed NNP on lattice parameters and phonon properties agree well with those obtained by DFT calculations. We also investigated the mixing energy of Au$_{1-x}$…
The generalized stacking fault (SFE) energy curves of pure gold (Au) and its binary alloys with transition metals are determined from density functional theory (DFT). Alloy elements Ag, Al, Cu, Ni, Ti, Zr, Zn, In, Ga, Sn, Mn, Cd, Sn, Ta and Cr are substituted into Au at concentrations up to 4%. A comparison of various proposed methodologies to calculate SFEs is given. The intrinsic SFE decreases for all alloying elements from its value for pure Au, but SFE energies (both stable and unstable) vary strongly with the distance of the alloying element from the stacking fault region, and with alloy …
Applying the approximate DFT-1/2 quasiparticle scheme, band structure unfolding, and generalized quasichemical approximation to describe chemical and structural disorder, we investigate the electronic structure of Bi$_{1-x}$Sb$_x$ alloys from first principles. We calculate the important energy levels near the Fermi energy versus the Sb concentration $x$ where the trivial-topological (TT) and semimetal-semiconductor (SMSC) transitions occur. We demonstrate that the energy variation of the relevant states deviates significantly from linear behavior and that the bowings are important to correctly…
The recent progress in formation of two-dimensional (2D) GaN by a migration-enhanced encapsulated technique opens up new possibilities for group III-V 2D semiconductors with a band gap within the visible energy spectrum. Using first-principles calculations we explored alloying of 2D-GaN to achieve an optically active material with a tuneable band gap. The effect of isoelectronic III-V substitutional elements on the band gaps, band offsets, and spatial electron localization is studied. In addition to optoelectronic properties, the formability of alloys is evaluated using impurity formation ener…
We have investigated the optoelectronic and thermoelectric properties of hexagonal antiperovskites Ba$_3$DN (D = Sb, Bi) using DFT calculations. The calculated equilibrium lattice parameters of both compounds are in good agreement with the available data. The calculated electronic structures indicate that they are direct bandgap semiconductors and the values of bandgaps are 1.35 and 1.33 eV for Ba3SbN and Ba3BiN, respectively. The inclusion of the spin-orbit effect split the conduction bands and the band gap of Ba$_3$BiN is much reduced. These two compounds have a high absorption coefficient, …
A comparative study of wurtzite ZnO doped by rare earth elements (Tm, Yb, Ce) have been investigated using density functional theory (DFT) based on the full-potential linearized augmented plane wave orbital (FP-LAPW) method, as implemented in Wien2K code. The structural parameters were calculated by PBEsol functional and in good agreement with the experimental data. The electronic (density of states, band structure) and optical (absorption coefficient, reflectivity, refraction index) properties were determined by TB-mBJ potential. The rare earth element doped ZnO have a significant impact on t…
Magnetic, Optoelectronic, and Rietveld refined structural properties of Al3+ substituted nanocrystalline Ni-Cu spinel ferrites: An experimental and DFT based study
In search of the ferromagnetic insulators for spintronic device applications, we have studied the electronic, optical, and magnetic properties ofLa2CrNiO6(LCNO) using the first principle density functional theory (DFT)and monte carlo simulation technique. Firstly, we have adopted the sol-gel method for preparation of LCNO and refined the X-ray diffracted value using the fullprof suite under the Rietveld mechanism. The obtained orthorhombic Pbnm and cubic Fm-3m space groups are used as the input of the DFT calculations. Both the structures have shown the half metallicity and insult-ing bandgap …
We perform high-throughput density functional theory (DFT) calculations for optoelectronic properties (electronic bandgap and frequency dependent dielectric function) using the OptB88vdW functional (OPT) and the Tran-Blaha modified Becke Johnson potential (MBJ). This data is distributed publicly through JARVIS-DFT database. We used this data to evaluate the differences between these two formalisms and quantify their accuracy, comparing to experimental data whenever applicable. At present, we have 17,805 OPT and 7,358 MBJ bandgaps and dielectric functions. MBJ is found to predict better bandgap…
Structural and optoelectronic properties of α, \{beta}, γ phases of calcium titanate are studied with the implementation of first-principles quantum-chemical calculations in the framework of DFT. When optimizing the geometry, the GGA approximation was used. The relaxed lattice parameters obtained by us are identical with the experimental analogs. It has been established that the most stable phase of calcium titanate is the orthorhombic syngony, which corresponds to the results of experimental measurements. It is shown that as the transition from the α-phase to the γ-phase proceeds, the lattice…
Alloying is a powerful tool for tuning materials that facilitates the targeted design of desirable properties for a variety of applications. In this work, we provide a comprehensive investigation of the synthetic accessibility and electronic properties of nine alkaline-earth chalcogenide anion alloys (CaS$_{1-x}$O$_x$, CaS$_{1-x}$Se$_x$, CaS$_{1-x}$Te$_x$, SrS$_{1-x}$O$_x$, SrS$_{1-x}$Se$_x$, SrS$_{1-x}$Te$_x$, MgS$_{1- x}$O$_x$, MgS$_{1-x}$Se$_x$, and MgS$_{1-x}$Te$_x$). We show that isostructural alloying within the rock salt structure is favored for all systems except MgS$_{1-x}$Te$_x$, whi…
Recently, direct bandgap double perovskites are becoming more popular among photovoltaic research community owing to their potential to address issues of lead (Pb) toxicity and structural instability inherent in lead halide (simple) perovskites. In this study, In-Ag based direct bandgap double perovskite, Cs2AgInCl6 (CAIC), is treated with transition metal doping to improve the optoelectronic properties of the material. Investigations of structural and optoelectronic properties of Cu-doped CAIC, Cs2Ag(1-x)CuxInCl6, are done using ab-initio calculations with density functional theory (DFT) and …
PbTaSe2 is a non-centrosymmetric topological semimetal. In this work we have explored the structural, elastic, mechanical, bonding, electronic, acoustic, thermal, and optical properties of PbTaSe2. The electronic bond structure calculations confirm semi-metallic character. Fermi surface topology shows both electron and hole sheets. The single crystal elastic constants reveal that PbTaSe2 is elastically stable. The compound is soft, brittle, and highly machinable at the same time. It also possesses very high level of dry lubricity. Various anisotropy indicators suggest that PbTaSe2 is elastical…
We fabricated ferroelectric Bi4Ti3O12 (BiT) single crystalline thin films site-specifically substituted with LaTMO3 (TM = Al, Ti, V, Cr, Mn, Co, and Ni) on SrTiO3 substrates by pulsed laser epitaxy. When transition metals are incorporated into a certain site of the BiT, some of BiT-LaTMO3 showed a substantially decreased band gap, coming from the additional optical transition between oxygen 2p and TM 3d states. Specifically, all alloys with Mott insulators revealed a possibility of band gap reduction. Among them, BiT-LaCoO3 showed the largest band gap reduction by ~1 eV, positioning itself as …
We have explored the mechanical, electronic, optical and thermoelectric properties of p-type half-Heusler compound BaAgP for the first time using density functional theory based calculations. The mechanical and dynamical stability of this compound is confirmed by studying the Born stability criteria and phonon dispersion curve, respectively. It is soft, ductile and elastically anisotropic. The atomic bonding along a-axis is stronger than that along c-axis. The calculated electronic structure reveals that the studied compound is an indirect band gap semiconductor. The analysis of charge density…
Cerium and its technologically relevant compounds are examples of anomalous mixed valency, originating from two competing oxidation states -- itinerant Ce$^{3+}$ and localized Ce$^{4+}$. Under applied stress, anomalous transitions are observed but not well understood. Here we treat mixed valency as an "alloy" involving two valences with competing and numerous site-occupancy configurations, and we use density functional theory with Hubbard U ($i.e.$, DFT+U) to evaluate the effective valence and predict properties, including controlling valence by pseudo-ternary alloying. For Ce and its compound…
Tailoring the Optoelectronic, Photocatalytic, Thermoelectric and Thermodynamic Properties of Halides Li2InBiX6 (X = Cl, Br, I) for Energy Conversion: A DFT Study
Princess Nourah Bint Abdulrahman University（公主诺拉·宾特·阿卜杜勒拉赫曼大学）；University of West Bohemia（西波希米亚大学）；University of Sargodha（萨尔戈达大学）；King Saud University（沙特国王大学）；Gachon University（迦南大学）
Unusual optoelectronic properties of diamondoids produce some discrepancies between experiments and the outstanding many-body calculation outputs. Therefore, many theoretical efforts are attracted to resolve these inconsistencies. Here first, by combining time-dependent density functional theory (TD-DFT) and Franck-Condon (FC) approximation, the effect of electron-phonon (e-ph) interaction on the optical gap (OG) of the smallest diamondoids and one of its derivatives is studied. Then, the surface effects on the e-ph coupling and the optical properties of these structures in a comparative manne…
We explain the nature of the electronic band gap and optical absorption spectrum of Carbon - Boron Nitride (CBN) hybridized monolayers using density functional theory (DFT), GW and Bethe-Salpeter equation calculations. The CBN optoelectronic properties result from the overall monolayer bandstructure, whose quasiparticle states are controlled by the C domain size and lie at separate energy for C and BN without significant mixing at the band edge, as confirmed by the presence of strongly bound bright exciton states localized within the C domains. The resulting absorption spectra show two marked …
Genome-Guided Interpretable Screening of Phase-Stable, Lead-Free Double Perovskite Absorbers for All-Inorganic Semiconductors, Sensors, and Photovoltaics with DFT-Validated Design Rules
Research and Analysis Institute, RAI Initiative Ltd（拉伊倡议有限公司研究与分析研究所）；Bangladesh University of Textiles（孟加拉国纺织大学）；Universiti Putra Malaysia（马来西亚博特拉大学）；Institute of Science Tokyo（东京科学大学）；University of Évora（埃武拉大学）；Daffodil International University（达富迪尔国际大学）；University of Idaho（爱达荷大学）；North Carolina A&T State University（北卡罗来纳州立农业技术大学）
We employ a descriptor based machine-learning approach to assess the effect of chemical alloying on formation-enthalpy of rare-earth intermetallics. Application of machine-learning approaches in rare-earth intermetallic design have been sparse due to limited availability of reliable datasets. In this work, we developed an `in-house' rare-earth database with more than 600$+$ compounds, each entry was populated with formation enthalpy and related atomic features using high-throughput density-functional theory (DFT). The SISSO (sure independence screening and sparsifying operator) based machine-l…
Two-dimensional (2D) binary transition-metal chalcogenides (TMCs) like molybdenum disulfide exhibits excellent properties as materials for light adsorption devices. Alloying binary TMCs can form 2D compositionally complex TMC alloys (CCTMCAs) that possess remarkable properties from the constituent TMCs. We adopt a high-throughput workflow performing density functional theory (DFT) calculations based on the virtual crystal approximation (VCA) model (VCA-DFT). We test the workflow by predicting properties including in-plane lattice constants, band gaps, effective masses, spin-orbit coupling (SOC…
High-Pressure DFT Study of BeX (X = S, Se, Te): Phonon Spectra, Optical Properties, and Thermodynamic Stability for Advanced Optoelectronic Applications
Tuning the opto-electronic properties through alloying is essential for semiconductor technology. Currently, mostly isovalent and isostructural alloys are used (e.g., group-IV and III-V), but a vast and unexplored space of novel functional materials is conceivable when considering more complex alloys by mixing aliovalent and heterostructural constituents. The real challenge lies in the quantitative property prediction for such complex alloys to guide their experimental exploration. We developed an approach to predict compositional dependence of both band-structure and electrical properties fro…
β-Ga2O3-Based Heterojunctions: Exploring Growth Orientations and Alloying on Electronic Properties
School of Mathematics and Physics, Queen’s University Belfast（贝尔法斯特女王大学数学与物理学院）；Tyndall National Institute, University College Cork（科克大学丁达尔国家研究所）；European Theoretical Spectroscopy Facility（欧洲理论光谱设施）
In the present study, the structural and hitherto uninvestigated mechanical (elastic stiffness constants, machinability index, Cauchy pressure, anisotropy indices, brittleness/ductility, Poissons ratio), electronic, optical, and thermodynamic properties of novel boron-rich compounds B6X (X = S, Se) have been explored using density functional theory. The estimated structural lattice parameters were consistent with the prior report. The mechanical and dynamical stability of these compounds have been established theoretically. The materials are brittle in nature and elastically anisotropic. The v…
Composition-controlled optical fingerprints and anisotropy of self-trapped excitons in double perovskites
Max Planck Institute for the Structure and Dynamics of Matter（马克斯·普朗克物质结构动力学研究所）；Center for Free-Electron Laser Science（自由电子激光科学中心）；Technion - Israel Institute of Technology（以色列理工学院）
Electronic and stability properties of quasi-2D alkylammonium perovskites are investigated using density functional theory (DFT) calculations and validated experimentally on selected classes of compounds. Our analysis is focused on perovskite structures of formula (A)$_2$(A$'$)$_{n-1}$Pb$_n$X$_{3n+1}$, with large cations A = butyl-, pentyl-, hexylammonium (BA, PA, HXA), small cations A$'$ = methylammonium, formamidinium, ethylammonium, guanidinium (MA,FA,EA,GA) and halogens X = I, Br, Cl. The role of the halogen ions is outlined for the band structure, stability and defect formation energies. …
In recent years, metal halide perovskites (MHPs) for optoelectronic applications have attracted the attention of the scientific community due to their outstanding performance. The fundamental understanding of their physicochemical features is essential for improving their efficiency and stability. Atomistic and molecular simulations have played an essential role in the description of the optoelectronic properties and dynamical behaviour of MHPs, respectively. However, the complex interplay of the dynamical and optoelectronic properties in MHPs requires the simultaneous modelling of electrons a…
DFT aided prediction of phase stability, optoelectronic and thermoelectric properties of A2AuScX6 (A= Cs, Rb; X= Cl, Br, I) double perovskites for energy harvesting technology
Tuning Optoelectronic Properties and Photoelectrochemical Performance of \b{eta}-TaON via Vanadium Doping
Mads Clausen Institute, University of Southern Denmark（南丹麦大学马兹·克拉斯延研究所）；Department of Materials Science and Engineering, School of Materials and Chemical Technology, Institute of Science Tokyo（东京科学院校材料化学技术学院材料科学与工程系）；Instituto Tecnológico de Chascomús (INTECH), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)（查斯科穆斯技术研究所，国家科学技术研究委员会）；Escuela de Bio y Nanotecnologías, Universidad Nacional de San Martín (UNSAM)（圣马丁国立大学生物与纳米技术学院）；Physical−Technical Institute, National Academy of Sciences of Tajikistan（塔吉克斯坦科学院物理技术研究所）；School of Optoelectronic Engineering and CQUPT-BUL Innovation Institute, Chongqing University of Posts and Telecommunications（重庆邮电大学光电工程学院及CQUPT-BUL创新研究院）；Center For Development of Nanotechnology at the National University of Uzbekistan（乌兹别克斯坦国立大学纳米技术开发中心）；Department of Applied Chemistry, School of Science and Technology, Meiji University（明治大学理学院应用化学系）；Institute for Aqua Regeneration, Shinshu University（信州大学水再生研究所）
The outstanding optoelectronics and photovoltaic properties of metal halide perovskites, including high carrier motilities, low carrier recombination rates, and the tunable spectral absorption range are attributed to the unique electronic properties of these materials. While DFT provides reliable structures and stabilities of perovskites, it performs poorly in electronic structure prediction. The relativistic GW approximation has been demonstrated to be able to capture electronic structure accurately, but at an extremely high computational cost. Here we report efficient and accurate band gap c…
A topological insulator possesses a bulk energy gap splitting the lowest empty band from the highest occupied electronic band. The electronic states at the surface (or edge in two dimensions), on the other hand, of a topological insulator are gapless and are protected by the time reversal symmetry. Such systems are promising for variety of optoelectronic, superconducting, thermoelectric and quantum computation related applications. We have studied elastic, mechanical, electronic, optical properties, bonding character and the electronic charge density distribution of ternary Bi2Te2Se topologica…
New generation Indium based lead-free Cs2InAgCl6 is a promising halide material in photovoltaic applications due to its good air stability and non-toxic behavior. But its wide band gap (>3 eV) is not suitable for solar spectrum and hence reducing the photoelectronic efficiency for device applications. Here we report a significant band gap reduction from 3.3 eV to 0.6 eV by substitutional doping and its effect on opto-electronic and opto-thermoelectric properties from first-principles study. The results predict that Sn/Pb and Ga & Cu co-doping enhance the density of states significantly near th…
DFT based investigation of structural, elastic, optoelectronic, thermophysical and superconducting state properties of binary Mo3P at different pressures
In this work we use density functional theory (DFT) to investigate the influence of semi-local exchange and correlation effects on the electronic and optical properties of zinc oxide. We find that the inclusion of such effects using the Tran-Blaha modified Becke-Johnson potential yields an excellent description of the electronic structure of this material giving energy band gap which is systematically larger than the one obtained with standard local functionals such as the generalized gradient approximation. The discrepancy between the experimental and theoretical band gaps is then significant…
Chalcogenide perovskites have emerged as non-toxic and stable photovoltaic materials, acting as an alternative to lead halide hybrid perovskites having similar optoelectronic properties. In the present work, we report the electronic and optical properties of chalcogenide perovskites AZrS$_3$ (A=Ca, Sr, Ba) by using the density functional theory (DFT) and many-body perturbation theory (MBPT viz. G$_0$W$_0$ and BSE). This study includes excitonic analysis for the aforementioned systems. The exciton binding energy (E$_\textrm{B}$) is found to be larger than that of the halide perovskites, as the …
Accurate computational predictions of band gaps are of practical importance to the modeling and development of semiconductor technologies, such as (opto)electronic devices and photoelectrochemical cells. Among available electronic-structure methods, density-functional theory (DFT) with the Hubbard U correction (DFT+U) applied to band edge states is a computationally tractable approach to improve the accuracy of band gap predictions beyond that of DFT calculations based on (semi)local functionals. At variance with DFT approximations, which are not intended to describe optical band gaps and othe…
The discovery of lead free all-inorganic alloyed double perovskites have revolutionized photovoltaic research, showing promising light emitting efficiency and its tunability. However, detailed studies regarding optical, exciton, polaron and transport properties remain unexplored. Here, we report a theoretical study on the variation of carrier-lattice interaction and optoelectronic properties of pristine as well as alloyed Cs$_2$AgInCl$_6$ double perovskites. We have employed many-body perturbation theory (G$_0$W$_0$@HSE06) and density functional perturbation theory (DFPT) to compute exciton bi…
Inorganic metal-halide cubic perovskite semiconductors have become more popular in industrial applications of photovoltaic and optoelectronic devices. Among various perovskites, lead-free materials are currently most explored due to their non-toxic effect on the environment. In this study, the structural, electronic, optical, and mechanical properties of lead-free cubic perovskite materials FrBX3 (B = Ge, Sn; X = Cl, Br, I) are investigated through first-principles density-functional theory (DFT) calculations. These materials are found to exhibit semiconducting behavior with direct bandgap ene…
Thiophene oligomers are an important class of organic materials for photovoltaic applications, owing to their unique optoelectronic properties. Recently it was suggested that incorporation of furan units to the thiophene chains, maintaining the chain structure, namely thienylfuran linear oligomers, can bring improvements to the final material. In this work, we present a theoretical study of thiophene, furan and thienylfuran short chains, up to 4 units. Structural and electronic properties were obtained using Hartree-Fock (HF) and Density Functional Theory (DFT) calculations plus beyond mean-fi…
