Numerical studies on a ternary AgInTe2 chalcopyrite thin film solar cell

This paper theoretically outlines a new n-AlSb/p-AgInTe2/p+-BaSi2 solar cell. The dominance of several factors such as depth, carrier density and defects of every layer on the photovoltaic (PV) outcome has been ascertained applying Solar Cell Capacitance Simulator (SCAPS)-1D computer-based simulator. The AgInTe2 (AIT) solar cell has been probed for finding the role of BaSi2 as a back surface field (BSF) layer. It is revealed that the device power conversion efficiency (PCE) increments from 30% to 34% owing to the use of BaSi2 semiconducting BSF with VOC = 0.90 V, JSC = 43.75 mA/cm2, FF = 86.42%, respectively. The rippling of the output parameters with respect to the change in series and shunt resistances has also been probed and demonstrated. All the findings reveal the prospect of n-AlSb/p-AIT/p+-BaSi2 dual-heterojunction thin film photovoltaic cell.

First-Principles Calculations of Thermoelectric Transport Properties of Quaternary and Ternary Bulk Chalcogenide Crystals

Chalcogenide crystals have a wide range of applications, especially as thermoelectric materials for energy conversion. Thermoelectric materials can be used to generate an electric current from a temperature gradient based on the Seebeck effect and based on the Peltier effect, and they can be used in cooling applications. Using first-principles calculations and semiclassical Boltzmann theory, we have computed the Seebeck coefficient, electrical conductivity, electronic thermal conductivity, power factor, and figure of merit of 30 chalcogenide crystals. A Quantum Espresso package is used to calculate the electronic properties and locate the Fermi level. The transport properties are then calculated using the BoltzTraP code. The 30 crystals are divided into two groups. The first group has four crystals with quaternary composition (A₂BCQ₄) (A = Tl; B = Cd, Hg; C = Si, Ge, Sn; Q = S, Se, Te). The second group contains 26 crystals with the ternary composition (A’B’Q₂) (A’ = Ag, Cu, Au, Na; B’ = B, Al, Ga, In; Q = S, Se, Te). Among these 30 chalcogenide crystals, the results for 11 crystals: Tl₂CdGeSe₄, Tl₂CdSnSe₄, Tl₂HgSiSe₄, Tl₂HgSnS₄, AuBSe₂, AuBTe₂, AuAlTe₂, AuGaTe₂, AuInTe₂, AgAlSe₂, and AgAlTe₂ are revealed for the first time. In addition, temperature-dependent transport properties of pure and doped AgSbSe₂ and AgSbTe₂ crystals with dopant compositions of AgSb_0.94Cd_0.06Te₂ and AgSbTe_1.85Se_0.15 were explored. These results provide an excellent database for bulk chalcogenides crucial for a wide range of potential applications in renewable energy fields.

Modulation of optical absorption in m-Fe1-xRuxS2 and exploring stability in new m-RuS2

A first-principle computational method has been used to investigate the effects of Ru dopants on the electronic and optical absorption properties of marcasite FeS2. In addition, we have also revealed a new marcasite phase in RuS2, unlike most studied pyrite structures. The new phase has fulfilled all the necessary criteria of structural stability and its practical existence. The transition pressure of 8 GPa drives the structural change from pyrite to orthorhombic phase in RuS2. From the thermodynamical calculation, we have reported the stability of new-phase under various ranges of applied pressure and temperature. Further, from the results of phonon dispersion calculated at Zero Point Energy, pyrite structure exhibits ground state stability and the marcasite phase has all modes of frequencies positive. The newly proposed phase is a semiconductor with a band gap comparable to its pyrite counterpart but vary in optical absorption by around 106 cm-1. The various Ru doped structures have also shown similar optical absorption spectra in the same order of magnitude. We have used crystal field theory to explain high optical absorption which is due to the involvement of different electronic states in formation of electronic and optical band gaps. Lӧwdin charge analysis is used over the customarily Mulliken charges to predict 89% of covalence in the compound. Our results indicate the importance of new phase to enhance the efficiency of photovoltaic materials for practical applications.

Prediction for electronic, vibrational and thermoelectric properties of chalcopyrite AgX(X=In,Ga)Te2: PBE + U approach

The electronic, vibrational and thermoelectric transport characteristics of AgInTe₂ and AgGaTe₂ with chalcopyrite structure have been investigated. The electronic structures are calculated using the density-functional theory within the generalized gradient approximation (GGA) of Perdew-Burke-Ernzerhof functional considering the Hubbard-U exchange correlation. The band-gaps of AgInTe₂ and AgGaTe₂ are much larger than previous standard GGA functional results and agree well with the existing experimental data. The effective mass of the hole and the shape of density of states near the edge of the valence band indicate AgInTe₂ and AgGaTe₂ are considerable p-type thermoelectric materials. An analysis of lattice dynamics shows the low thermal conductivities of AgInTe₂ and AgGaTe₂. The thermoelectric transport properties' dependence on carrier concentration for p-type AgInTe₂ and AgGaTe₂ in a wide range of temperatures has been studied in detail. The results show that p-type AgInTe₂ and AgGaTe₂ at 800 K can achieve the merit values of 0.91 and 1.38 at about 2.12 × 10²⁰ cm^-3 and 1.97 × 10²⁰ cm^-3 carrier concentrations, respectively. This indicates p-type AgGaTe₂ is a potential thermoelectric material at high temperature.