Undoped System Research Articles

Exploring the electronic transport, magnetic, and optical properties of strongly correlated systems: A numerical analytical continuation approach

The electronic, magnetic and optical properties of the double perovskites Ca2NiOsO6 and Fe-doped derivative were calculated using the full potential linearized augmented plane wave technique through the GGA + U with PBE exchange correlation functionals. The calculations show that both of the systems are half-metallic with Fe-doped system as a ferromagnet, whereas the undoped system shows the ferrimagnetic ordering. Additionally, the study is extended for calculating the Mott parameters through dynamical mean field theory (DMFT) with the maximum entropy model (MEM). It is found that the MIT model parameters (U, [Formula: see text]) for Ca2NiOsO6 and Ca2Fe[Formula: see text]Ni[Formula: see text]OsO6 systems are (5.7[Formula: see text]eV, 6.0[Formula: see text](eV)[Formula: see text]) and (6.0[Formula: see text]eV, 6.0[Formula: see text](eV)[Formula: see text]), respectively. Furthermore, the calculations agree with optical Drude peak analysis. The optical conductivity, reflectivity, absorptivity, ELOSS function, dielectric function refractive index and sum-rule are also explored in relation to the photoinduced behaviors of the materials.

Separation of electric and thermal transport with in-situ precipitates matrix in Ca3Co4O9+δ

Suppressing the thermal conductivity of materials through the reduction of the particle sizes has long been applied to enhance the thermoelectric performance of nanostructured materials. Maintaining a high electrical conductivity in the as-formed nanostructure that is comparable to its bulk materials, is equally important in determining the final thermoelectric behavior of the nanostructure. However, this is not always attainable since the phononic and electronic transport in solids is often interdependent on each other. Naturally occurring with a complex layered structure, bulk polycrystalline Ca3Co4O9+δ has been selected to investigate the subtle correlation between electronic and phononic subsystems, which is still challenging for complex thermoelectrics. By combining high-energy ball milling and spark plasma sintering (SPS), we generate a novel structure of CCO matrix with in-situ precipitates, in which the bar-shaped CCO grains form a three-dimensional network, and the Co3O4 polyhedrons are found to be attached to the CCO grain surfaces with CaCO3 nano-precipitates filling the network space. The CCO grains serve as electrical paths to maintain the high electrical conductivities, while the in-situ precipitates, especially CaCO3, have significantly blocked the phonon transport in the bulk CCO samples with nanocrystalline grains, thus greatly reducing the thermal conductivity. Electrochemical analysis and the modified Debye-Callaway calculation provide a substantial understanding for the transport of charge carriers and phonons. A record zT value of 0.5 with ultra-low thermal conductivity of 0.496 Wm−1K−1 at 973 K are achieved in the CCO-66 sample. To date, this is the highest reported zT value in undoped polycrystalline CCO material systems.

Structural evolution and oxidation resistance of polysilazane‐derived SiCN–HfO2 ceramics

AbstractPolymer‐derived SiCN materials have great application potential in high‐temperature environments. In the current work, SiCN ceramics were tailored with Hf incorporation through doping of a molecular precursor in the preceramic polymer. The ceramics remained in a single amorphous phase up to 900°C. Further annealing caused nucleation and crystallization of tetragonal hafnium oxide (t‐HfO2) within the SiCN matrix, resulting in a unique glass–ceramic nanocomposite of t‐HfO2–SiCN. The crystal sizes of t‐HfO2 were in the range of 2.3–5.1 nm. Raman spectroscopy was employed to examine the effect of Hf‐doping on the phase separation and crystallization of sp2‐carbon. Thermal stability in an oxidizing environment was analyzed by thermogravimetry. The incorporation of Hf in the SiCN ceramic system led to improved phase stability and oxidation resistance compared to the undoped SiCN system.

Effects of framework dopants on luminescent properties of red nitride phosphors via band structure modelling

Currently, researchers have been able to manipulate the luminescent properties and thermal stability of nitride red phosphor Sr2Si5N8:Eu2+ through rare earth doping. However, there is limited research on the doping of its framework. This work investigated the crystal structure, band structure, and luminescence properties of Sr2Si5N8: Eu2+ and its framework doped systems. We selected B, C, and O as doping elements because the corresponding formation energies of these elements doped structures are relatively low. Then, we calculated the band structures of various doped systems in both the ground and excited states. This analysis aimed to investigate their luminescent properties using the configuration coordinate diagram. The results show that doping with B, C, or O has minimal effect on the emission peak width. The thermal quenching resistance of the B- or C-doped system was enhanced due to the increased energy differences between the 5d energy level of the electron-filled state in the excited state and the bottom of the conduction band, compared to the undoped system. However, the thermal quenching resistance of the O-doped system varies depending on the position of the silicon vacancy. The work indicates that framework doping can also improve the thermal quenching resistance of phosphors besides rare earth ions doping.

Plasma Excitations in SiGe/Si Quantum Wells

Plasma and magnetoplasma excitations in high-quality undoped two-dimensional electron systems based on SiGe/Si quantum wells are studied in detail. A two-dimensional electron system is formed by applying a vo-ltage to the top gate, which is partially transparent to subterahertz radiation in the frequency range of 20‒160 GHz. The results for SiGe/Si quantum wells with a Sb δ-doping layer are also presented for comparison. The transport and quantum scattering times for both structures are directly determined. It has been found that the effective electron mass is almost independent of the two-dimensional electron density in a wide density range.

Magnetocaloric effect in the Ising model with RKKY interaction on the Shastry–Sutherland lattice

The classical Monte Carlo method is used to examine effects of electron and hole doping on the magnetocaloric effect in the generalized 2D Ising model with the long-range RKKY interaction on the Shastry–Sutherland lattice. The electron and hole doping in this model is controlled by deviations of the Fermi wave vector kF from the initial value kF=2π/1.24 which models the most realistically situation in the undoped metallic Shastry–Sutherland rare-earth tetraboride TmB4. For the undoped case we have found a heating hill (the entropy change ΔS>0) occurring in the vicinity of metamagnetic transitions and a cooling depression in the paramagnetic phase which is in a very good qualitative agreement with experimental measurements in TmB4. In the case of small electron doping (kF=2π/1.26), a significant decrease of the maximum of −ΔS is observed, while in the strongly hole (electron) doped case kF=2π/1.17 (kF=2π/1.43) the maximum of −ΔS is considerably enhanced against the undoped system, which points to the fact that some of doped systems could have better cooling properties than the undoped one. This is confirmed independently by calculations of relative cooling power for a wide range of parameter kF, where we have found two intervals kF∈〈2π/1.15,2π/1.21〉 and kF∈〈2π/1.39,2π/1.5〉 with much larger relative cooling power in comparison to the undoped case.

Thermodynamics and robust n-type charge carrier density in Co-doped FeTe2: strain strategy

Herein, we investigated the combined effect of Co-doping and strain (biaxial [110] and hydrostatic [111]) on the thermodynamics and electronic structure of the FeTe2 motif using ab-initio calculations by considering the strong correlation effects. The pristine one has a non-magnetic semiconducting nature with an indirect band gap (E g ) of 0.384 eV. Interestingly, our results revealed that the Co-doping at the Fe site induced an n-type conductivity (i.e. few states are crossing the Fermi level from the valence to conduction band) in the system having a substantial charge carrier density magnitude of 0.14 × 1021 cm−3. The metallicity mainly comprises the Co-3d orbitals along with a significant contribution from Fe-3d states. Thermodynamic, mechanical, and dynamical stability of the Co-doped FeTe2 structure is confirmed by computing the formation energetic, elastic constants, and phonon band structure, respectively. Generally, an increasing and decreasing trend in E g value is evident against the applied compressive and tensile strains having ranged from −5% to +5% for the case of the undoped system, respectively. On the other hand, the Co-doped structure maintained its n-type conduction against considered both types of strains. Moreover, it is demonstrated that compressive strains strengthen the charge carrier density amplitude, while tensile strains show a negative impact. Hence, the present work displays that robust n-type conductivity and stable structure of Co-doped FeTe2 system, makes it a desirable candidate for device applications.

Study on the Electronic Structure and Optical Properties of (K, Rb, Cs, Fr) Doped CoSi Based on the First Principle

In this paper, the band structure, density of States and optical properties of CoSi, K, Rb, Cs and Fr doped CoSi are calculated by first principles. It is found that the bottom and top of the conduction band pass through the Fermi level before and after doping, showing metal properties. The static permittivity of undoped CoSi, K, Rb, Cs and Fr doping is 28.9,154,168,110,105 respectively, which indicates that the static permittivity is improved after doping the refractive index of doped K, Rb, Cs and Fr increases compared with that of undoped CoSi. After doping, the maximum imaginary part of dielectric constant is 18.4; 608; 56; 32.9; 31 respectively.CoSi, K-CoSi, Rb-CoSi, Cs-CoSi and Fr-Cosi have strong absorption of light in the far ultraviolet region, and the maximum absorption coefficients are 3.83, 3.69, 3.37, 3.34 and 3.33 respectively. The maximum reflection peak of undoped CoSi is 0.807, that of K-doped system is 0.774, that of Rb-doped system is 0.713, that of Cs-doped system is 0.731, and that of Fr-doped system is 0.758. It can be seen that the reflectivity of doped CoSi decreases, and the reflectivity of Rb-doped system is the smallest Compared with the undoped system, the photoconductivity of the doped system moves to the high energy region, resulting in a blue shift.

Thermodynamics evaluation of half-metallic ferromagnetism in N-doped XTiO3 (X = Ca, Sr, and Ba) systems: DFT calculations

Half-metallic (HM) materials with high magnetic transition temperature (TC) combined with a wide energy gap (Eg) in insulating spin channel are desired for the realization of modern spin based devices due to their stable ferromagnetic (FM) ordering, spin-filtering, and high mean free path. Herein, the formation energetics, electronic, and magnetic characteristics of N-doped XTiO3 (XTO) (X = Ca, Sr, and Ba) perovskite oxides (PO) were inspected by first-principles calculations, where one of the oxygen (O) atom is replaced by nitrogen (N) atom. The calculated formation energy and elastic constants values confirm the thermodynamical as well as elastic stability of all doped systems. Our calculations show that all undoped PO systems display a non-magnetic insulating behavior. On the other hand, all doped motifs show magnetic character with an integral induced magnetic moment of 1.00 μB. Further, it has also been observed that magnetism in all these doped systems mainly originates from p orbitals of the dopant N. Interestingly, all doped systems have 100% spin splitting at Fermi level depicting a HM FM behavior with large Eg of 1.61, 1.65, and 1.59 eV in spin minority channels for XTO (X = Ca, Sr, and Ba) systems, respectively. Further, a long range stable FM ordering with TC > RT is predicted in these doped materials by computing the magnetic energy solutions for FM and anti-ferromagnetic (AFM) ordering at various distances between two N atoms. The current study suggests that doping strategy with non-magnetic dopant in different PO materials could be a useful approach to modulate the physical features and make them effective for emerging spintronic devices operating above RT.

Light Conversion upon Photoexcitation of NaBiF4:Yb3+/Ho3+/Ce3+ Nanocrystalline Particles.

NaBiF4 nanocrystalline particles were synthesized by means of a facile precipitation synthesis route to explore upconversion emission properties when doped with lanthanide ions. In particular, the incorporation of the Yb3+-Ho3+-Ce3+ triad with controlled ion concentration facilitates near-IR pumping conversion into visible light, with the possibility of color emission tuning depending on Ce3+ doping amount. We observed that introducing a Ce3+ content up to 20 at.% in NaBiF4:Yb3+/Ho3+, the chromaticity progressively turns from green for the Ce3+ undoped system to red. This is due to cross-relaxation mechanisms between Ho3+ and Ce3+ ions that influence the relative efficiency of the overall upconversion pathways, as discussed on the basis of a theoretical rate equation model. Furthermore, experimental results suggest that the photoexcitation of intra-4f Ho3+ transitions with light near the UV-visible edge can promote downconverted Yb3+ near-IR emission through quantum cutting triggered by Ho3+-Yb3+ energy transfer mechanisms. The present study evidences the potentiality of the developed NaBiF4 particles for applications that exploit lanthanide-based light frequency conversion and multicolor emission tuning.

Optoelectronic, mechanical, and thermoelectric properties of Na/I co-doped SnSe via ab initio calculations

Tin selenide-based materials have attracted much attention recently because of their unique properties. This study investigates the effect of Sodium and Iodine co-doping on the optoelectronic, mechanical, and thermoelectric properties of orthorhombic SnSe via First-principles calculations. Na/I co-doped crystal was found to have a triclinic structure, and its electronic bandgap is 0.325 ​eV, whereas the calculated band gap of the pristine SnSe is 0.824 ​eV using SCAN functional. Na/I co-doping alters the Fermi level of SnSe up to its conduction bands, resulting in an n-type system. Furthermore, the static dielectric constant shows that the doped system could be suitable for capacitors and solar cell applications. According to the calculated elastic constants, the doped system is stable. Moreover, it has a negative Poisson's ratio value suggesting it's auxetic sensor material. The thermoelectric performance is examined from 300 ​K to 800 ​K across a broad range of carrier concentrations for the doped and undoped SnSe systems. We have found that Na/I co-doping enhances the electrical conductivity and the Seebeck coefficient of SnSe. The highest power factor calculated for the doped system was 27.9μV/Kcm at carrier concentration of n≅−3×1020cm−3.

First principles study of the effect of (Mg, C) doping and Zn vacancies on the carrier activity, lifetime, visible light effect, and oxidation–reduction reaction of ZnO(0 0 1) monolayers

At present, some progress has been made in the study of Mg doping on the photocatalytic performance of ZnO monolayers. However, few studies on the effects of C impurities, Mg doping, and Zn vacancy coexistence on the electronic structure and photocatalytic performance of ZnO monolayers have been conducted. The preparation of ZnO through metal organic chemical vapor deposition growth technology inevitably generates C impurities, which are difficult to remove. To solve such problems, we investigated the effects of Mg doping and the coexistence of C impurities and Zn vacancies on the electronic structure and the photocatalysis of ZnO monolayers with a generalized gradient approximation plane-wave ultrasoft pseudopotential method based on the framework of density-generalized functional theory. Results showed that all doped systems had negative formation energy under O-rich conditions, indicating that the systems easily formed. The cohesion energy of Zn33CiCZnMgO36(Ci1−/2+/3+/4+,CZn2+) monolayers was relatively large, and the systems were stable. The absorption spectra of the doped systems red-shifted in a wavelength range of 425–800 nm compared with the absorption spectrum of the undoped Zn36O36 monolayer system. All doped systems were able to react with water to produce H2 and O2 at pH of 0 or 7. The Zn34CiCOMgO35 (Ci1−,CO2−) monolayer exhibited the strongest activity, the best absorption spectrum red shift, the smallest work function, the longest carrier lifetime, and the best HER ability. The Zn34CiCOMgO35 (Ci1−,CO2−) monolayer was considered a strong candidate for photocatalytic hydrogen production. Overall, this study has a theoretical reference value for the design and preparation of novel photocatalytic functional materials.

Diffusion in undoped and Cr-doped amorphous UO2

UO2 fuel pellets are often doped with chromium oxide to obtain favourable properties such as higher density, improved thermal stability, large grain sizes, improved pellet-clad interaction margins, and increased fission gas retention during transients. Chromium has a low solubility limit in UO2, with past experimental work reporting solubility limits ranging between 0.004 to 0.06 wt.% Cr. Due to its low solubility, segregation of Cr ions to the grain boundary may occur. Further, the complexity of these boundaries may be high as observed in other ceramics resulting in disordered or amorphous regions along the boundary, affecting a range of material and operational properties of the fuel pellet. To assess these disordered regions, in this work we study amorphous undoped and Cr doped UO2 systems (containing 10–50 at.% Cr3+) that have been modelled using classical molecular dynamics methods incorporating Cr3+ into the well-used CRG potential library. Diffusion coefficients, pre-exponential factors, and activation energies for diffusion were computed for oxygen ions, assessing the impact of structure and extrinsic species on migration. Oxygen diffusion was observed to be much faster in the undoped amorphous system compared to its crystalline counterpart. Oxygen diffusion in doped systems decreased with increasing Cr concentration, highlighting the importance of additives to retain fission products and other migratory species.

Charge Balanced Vacancy Engineering to Enhance the Thermoelectric Properties of GeMnTe2

As a derivative of GeTe and MnTe, GeMnTe2 exhibits a cubic structure with no phase transition. Compared to GeTe, it is considerably cheaper and has a significantly high carrier concentration compared to MnTe, making it an excellent thermoelectric (TE) material with promising applications. Herein, a charge‐balanced vacancy engineering strategy is employed, resulting in a significant improvement in the power factor of GeMnTe2. Furthermore, the density functional theory calculation shows that the doping of Bi and the absence of Ge synergically increase the density of states near the Fermi level. Power factors of ≈13.7 μW cm−1 K−2 are achieved at 8% Bi content, a 22% improvement compared to the undoped system, while a final maximum ZT value of about 1.12 and an average ZT value of 0.72 are achieved. This indicates that charge‐balance vacancy engineering is an effective optimization method for the GeMnTe2 system, which can effectively improve the TE performance.

Effect of precious metals (Ru, Rh, Pd, Os, Ir, Pt, Co) on structural, stability and ductility of Fe5Ni4S8 (P4_2/nmc) pentlandite: cluster expansion method

This work investigated the effects of PGEs on structural, stability and ductility of Fe5Ni4S8 (P4_2/nmc). The cluster expansion (CE) method was used to predict the most stable (Fe,Ni)9S8 and further doped platinum group element on octahedral site iron of Fe5Ni4S8 (P4_2/nmc) Pn system. The structural and ductility of the most stable M(Fe,Ni)8S8 (M= Ru, Rh, Pd, Os, Ir, Pt) were investigated and compared to structural and ductility of Fe5Ni4S8 (P4_2/nmc) i.e undoped system. It was noted that doping PGEs on octahedral site of Fe5Ni4S8 (P4_2/nmc) did not change the symmetry, however the PGEs increased the ductility of Fe5Ni4S8 (P4_2/nmc)

Enhanced anodic catalytic performance in PrFeO3-δ of perovskite materials via Co-doping with Sr and VB subgroup metals (V, Nb, Ta).

The anodic catalytic capability of PrFeO3-δ is restricted by the Fe-site element type in the perovskite material structure due to its low electrical conductivity of electrons. Here, we present a strategy for tuning the Fe-site element type via Sr and VB subgroup metals (V, Nb, Ta) co-doping to enhance the anodic catalytic performance of PrFeO3-δ anode materials. Our calculations show that Sr and Nb co-doping has suitable hydrogen adsorption energy for PrFeO3-δ anode materials, and its adsorption energy is adjusted to -0.717 eV, which is more suitable to absorb the hydrogen molecule than other high-profile perovskite anode materials. Meanwhile, after the doped surface is adsorbed by hydrogen molecules, the bond length lengthens until it breaks, and one of the broken hydrogen atoms moves directly above the surface oxygen atom, which is beneficial for accelerating the anodic catalytic reaction. Thus, the Pr0.5Sr0.5Fe0.875Nb0.125O3-δ material is a promising perovskite anode catalyst. Interestingly, the stability of PrFeO3-δ is significantly affected by the oxygen vacancy content; the structural stability of the undoped system can be maintained via Sr and Nb co-doping to avoid decomposition, which provides new thinking to maintain the high stability of perovskite ferrite materials. Furthermore, we find that relative to the PrFeO3-δ, the Pr0.5Sr0.5Fe0.875Nb0.125O3-δ surface of hydrogen adsorption has obvious charge transfer and upward shift of the d-band center. Our anodic catalytic theoretical work shows that Sr and Nb co-doping can effectively enhance the catalytic performance of the PrFeO3-δ ferrite materials.

Emergence of robust half-metallic spin gap and a sizeable magnetic anisotropy in electron-doped Ca[formula omitted]FeOsO[formula omitted

Half-metallic materials having a large band gap (Eg) along with giant magnetocrystalline anisotropy energy (MAE) have been proposed to be crucial for the development of magnetic tunnel junctions. Herein, electron-doped Ca2FeOsO6 (CFOO) double perovskite oxide is investigated by employing ab-initio calculations with the inclusion of Hubbard U and spin–orbit coupling effects. Electron doping is realized by introducing Co+2/Ni+2 ion with 3d7 (t2g3↑t2g2↓eg2↑eg0↓)/3d8 (t2g3↑t2g3↓eg2↑eg0↓) configuration at Fe+33d5 (t2g3↑t2g0↓eg2↑eg0↓) site. The thermodynamical, mechanical, and dynamical stability of these motifs for determining the synthesis feasibility at ambient conditions is established by calculating the formation energetics, elastic constants, and phonon band structure, respectively. The undoped CFOO system displays a ferrimagnetic Mott-insulating behavior due to a strong antiferromagnetic coupling between Fe and Os ions. On the other hand, electron doping induces half metallicity in CFOO, where extra electrons provided by TM-dopants produce a repulsion in the partially filled Os t2g3↓ spin-minority channel. As a consequence, the Os bands near the Fermi level are shifted to higher energetics; resulting in a conducting nature for the doped motifs. Therefore, Os ion remains in the mixed formal valence states of Os+5 and Os+6/Os+7, which reduces the moments as well. Most remarkably, a large Eg of 1.26/1.65 eV exists in the spin-majority channel of Co/Ni-doped structure, which is highly desired to effectively suppress the spin-flipping and affirm the large mean free path for spins along with a high spin-filtering response. Our results also demonstrated that the half metallicity of the studied TM-doped CFOO is robust and can be preserved under a reasonable magnitude of biaxial strains ([110]). Additionally, a sizeable MAE constant of ∼×107 erg/cm3 indicates that these materials could be potential candidates for the data storage devices.

Effects of metal-based additives on dehydrogenation process of 2NaBH4 + MgH2 system

We report a systematic investigation of the effect that selected metal-based additives have on the dehydrogenation properties of the reactive hydride composite (RHC) model system 2NaBH4+MgH2. Compared to the pristine system, the material doped with 3TiCl3·AlCl3 exhibits superior dehydrogenation kinetics. The addition of 3TiCl3·AlCl3 alters the controlling mechanism of the second dehydrogenation step making it change from a two-dimensional interface controlled process to a two-dimensional nucleation and growth controlled process. The microstructural investigation of the dehydrogenated 2NaBH4+MgH2via high-resolution transmission electron microscopy (HRTEM) shows significant differences in the MgB2 morphology formed in the doped and undoped systems. The MgB2 has a needle-like structure in the sample doped with 3TiCl3·AlCl3, which is different from the plate-like MgB2 structure in the undoped sample. Moreover, nanostructured metal-based phases, such as TiB2/AlB2 particles, acting as heterogeneous nucleation sites for MgB2 are also identified for the sample doped with 3TiCl3·AlCl3.

A DFT investigation on theranostic potential of alkaline earth metal doped phosphorenes for ifosfamide anti-cancer drug

Cancer is one of the leading causes of human mortality and a theranostics strategy is essential for its effective treatment. Density function theory (DFT) simulations were executed to examine the drug delivery, photothermal potential, and photoimaging guided cancer diagnostic potential of pristine and alkaline earth metal (M=Be, Mg, and Ca) doped phosphorenes (M-PH). The topological, electronic, and thermodynamic descriptors of M@PH and Ifosfamide (IFO) loaded systems (IFO@M-PH) were calculated. The oxygen atoms of IFO coordinated with the doped M-PH carrier. The adsorption process was exothermic and hence spontaneous. A higher adsorption energy was found for IFO@M-PH systems compared to undoped system. The polarity of the drug-carrying system is increased after doping which is favorable for effective in vivo drug flow. The HOMO-LUMO and natural bond orbital (NBO) analyses revealed that doping facilitated the charge transfer from drug to phosphorene. The quantum theory of atoms in molecules (QTAIM) and non-covalent interaction (NCI) studies show the presence of weak non-covalent interactions among the drug and substrate, supporting the effective drug release. The excited-state calculations for drug loaded complexes show the shifting of λmax from 434 nm to Near-Infrared (NIR) region. This supported IFO@M-PH as a potential candidate for photothermal therapy and photoimaging guided cancer diagnostic.

A DFT Study of Structure, Electronic and Optical Properties of Se-Doped Kesterite Cu2ZnSnS4 (CZTSSe)

In this work, we have studied the geometric structure and electronic and optical properties of Cu2ZnSn(S1-xSex)4 nanocrystals where x = 0, 0.25, 0.50, 0.75, 1.00 by the quantum-chemical calculations within the framework of DFT. For the electronic and optical properties calculations, the effective XC functional and the TB-mBJ potential were used. The calculated structural characteristics show that the volume of these systems increases with increasing the Se concentration. The electronic properties of the Se-doped kesterite Cu2ZnSnS4 show that the bandgap tends to decrease. It was found that the Se-doped material has noticeably increased its absorption capacity. Hence, the efficiency of the Cu2ZnSnS4 in the IR region of radiation improves. The effective reduction bandgap from 1.455 eV to 0.94 eV is observed, which is in gоod agreement with known experimental data for the pure and undoped systems Cu2ZnSnS4 and Cu2ZnSnSе4. The calculated band gap is 1.346 eV for the Cu2ZnSnS3Se system, which is comparable with the optimal bandgap of semiconductors used in photovoltaic applications. It was found that with the increase of the Se concentration, the absorption coefficient increases, thereby resulting in the materials' reflectivity decrease. The calculated optoelectronic parameters and the density of electronic states indicate that the Cu2ZnSnS4:Se system possesses a favorable property, suitable for applications in solar cells technology.