Figure - available from: RSC Advances
This content is subject to copyright. Terms and conditions apply.
Structure of crystalline MoO3 in ball-and-stick and polyhedral representation. The molybdenum (Mo) atom is in purple and the three oxygen (O) sites are in three different shades of red
Source publication
Molybdenum trioxide (MoO3) is a promising material for energy conversion applications, including recent uses as a hole selective contact in silicon photovoltaic devices. The electrical and chemical properties of MoO3 are known to be strongly sensitive to the presence of intrinsic and extrinsic defects, which in turn are dependent on the fabrication...
Similar publications
We propose new multi-dimensional atom optics that can create coherent superpositions of atomic wavepackets along three spatial directions. These tools can be used to generate light-pulse atom interferometers that are simultaneously sensitive to the three components of acceleration and rotation, and we discuss how to isolate these inertial component...
The power output and the efficiency of a thermophotovoltaic (TPV) system are determined by the radiation from a heat source, TPV cells, system parasitic losses, cell cooling subsystems, etc. The cells are core devices of a system, and the performance of the cells can be characterized by a number of parameters, including open circuit voltage (Voc),...
Hybridogenesis is an unusual form of reproduction that is found in hybrids between different species. It involves the selective transmission of one of the parental genomes, while the other one is renewed by mating with the corresponding species. It is seen as a form of sexual parasitism, in which the hybridogenetic genome gains a twofold transmissi...
Inthe present study, 450 fish samples were collectedwhich included225 individuals of Planiliza abu and 225 individuals of Leuciscus vorax during the period from April 2018 to January 2019 from Euphrates River passing through Al-Mahdi area in Al-Muthanna province by using gill nets. The results of the microscopic examination showed a parasitic infec...
Citations
... Therefore, in this work, we undertake a systematic study of the variation of magneto-optoelectronic properties of α-MoO 3 with different defects (vacancies) and also to understand the stability of the system in response to these defects. In most previous studies of vacancies in α-MoO 3 , predominantly O vacancies were considered [28,30,52,53]. In the present work, along with the O vacancy, the Mo vacancy, and Mo-O co-vacancies have also been considered. ...
Semiconducting oxides possess a variety of intriguing electronic, optical, and magnetic properties,
and native defects play a crucial role in these systems. In this study, we study the influence of
native defects on these properties of α-MoO 3 using the first-principles density functional theory
(DFT) calculations. From the formation energy calculations, it is concluded that Mo vacancies are
difficult to form in the system, while O and Mo-O covacancies are energetically quite favorable.
We further find that vacancies give rise to mid-gap states (trap states) that remarkably affect
the magneto-optoelectronic properties of the material. Our calculations indicate that a single Mo
vacancy leads to half-metallic behavior, and also induces a large magnetic moment of 5.98 μ B . On
the other hand, for the single O vacancy case, the band gap disappears completely, but the system
remains in the non-magnetic state. For Mo-O co-vacancies of two types considered in this work, a
reduced band gap is found, along with an induced magnetic moment of 2.0 μ B . Furthermore, a few
finite peaks below the main band edge are observed in the absorption spectra of configurations with
Mo and O vacancies, while they are absent in the Mo-O co-vacancies of both types, just like in the
pristine state. From the ab-initio molecular dynamics simulations, stability and sustainability of
induced magnetic moment at room temperate is verified. Our findings will enable the development
of defect strategies that maximize the functionality of the system, and further help in designing
highly efficient magneto-optoelectronic and spintronic devices.
... The electrons then go to the newly added Ti interstitial state (which is slightly underneath the Ti interstitial state). The electrons then go to the valance band, where they emit blue light [23]. In comparison to pure TiO 2 and singly doped materials, the fluorescence spectra demonstrate that the co-doped materials exhibit decreased photoluminescence intensities. ...
A simple precipitation process was used to make Bismuth and Boron co-doped TiO2 nanorod like particles. To investigate the structural, geometrical, light absorption, and photocatalytic characteristics of the materials, a variety of spectroscopic and quantitative methods were used. According to the findings, all the materials had a highly crystalline anatase structure. The crystalline was attained to be 34 nm, 32 nm, 30 nm and 25 nm, respectively, for TiO2, Bi:TiO2, B:TiO2, and Bi–B:TiO2. From the optical study, band gap energies are achieved to be 3.07, 2.89, and 2.70 eV from the synthesized B:TiO2, Bi:TiO2, and Bi–B:TiO2 nanomaterials. From the observed morphological analysis, spherical shape and rectangular rod-like structure was attained and sizes of the particles are achieved to be range 50–300 nm, approximately. The laboratory findings also suggest that Bi and B ions have been doped into the TiO2 crystal lattice. The produced materials’ photocatalytic potential was investigated. Bi–B co-doped materials showed improved activity for degradation of methylene blue dye under stimulated solar-light irradiation as compared to pure TiO2, B and Bi individually doped TiO2. The experiment was also carried out with various beginning solution pH values, such as 2, 4, 6, and 8, to investigate the role of pH in the degradation process.
... We already know that NiO acts as hole-selective contact, due to lower valence band-offset and high work function, but the same does not apply for MoO x and some other hole-selective TMOs for Si. MoO x [16,22,25,47,81,106,[115][116][117][118][119][120][128][129][130][131][132][133][134][135][136][137][141][142][143][144][145][146][147][148][149][150][151][152][153][154][155]194,165,167,168,169,170] is the most explored hole-selective TMO given in Table 3. A review has been done on Si solar cells [126] featuring hole selective MoO x alone. ...
... Even ZnO has an amphoteric property to act as a hole-selective oxide [184] although it has been used as an electron-selective oxide in most cases [28,29,[201][202][203]. Similar studies have been done on hole-selective MoO 3 with Si [115] showing the variation of intrinsic and silicon defects in MoO 3 that cause stoichiometric defects. ...
The basics of dopant-free materials used as carrier-selective layers at the surfaces and interfaces in c-Si or poly-Si solar cells have been reviewed. Emphasis has been given to the discussion of a host of transition metal oxides (TMOs) having wide range of band structures and which have the carrier selective property of allowing only one type of carrier (electron or hole) to flow across their junctions with Si. The fabrication process of these materials are benign and at low temperatures which make them gradually attractive over the doped Si layers which need toxic materials and/or high temperatures for their formation. Silicon solar cells having dopant-free carrier selective TMOs fabricated by various groups using different fabrication processes and different contact configurations (Full area contacts, Partial area contacts or Interdigitated back contacts) have been reviewed and presented alongwith their photovoltaic performance. Different passivation schemes (full area or partial area) that could be used alongwith these dopant-free carrier selective materials have also been discussed.
... The formation energy E f (D q Ni ) of charged intrinsic and extrinsic defects in NiO were calculated following (1) [26], [27], [37] ...
... The chemical potential (μ i ) of Ni, O, and extrinsic metal cations were calculated using the literature method [26], [37]. This method assumes that the transition metal dopants are in thermodynamic equilibrium with a reservoir of TMO when they are synthesized under O-rich conditions, which is the case for most NiO films. ...
Transition metal oxides such as MoO
<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub>
, WO
<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub>
, V
<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>
O
<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5,</sub>
and NiO have shown potential as hole-selective passivating contact for crystalline silicon (c-Si) solar cells. Among them, NiO is a notoriously poor hole-conducting semiconductor. Doping metal oxide with multivalent metal cations is an effective method to modify their electronic properties because dopant-induced favorable defect states play a crucial role in charge carrier transport in device applications. We use first-principles density functional theory to identify suitable metal cations that favorably affect the hole-conducting properties of NiO. We identify Al, Mg, and Zn as suitable dopants for NiO, improving ohmic contact properties with c-Si. Subsequently, Al-doped NiO (Al
<sub>x</sub>
Ni
<sub>y</sub>
O) films were synthesized onto c-Si using an atomic layer deposition supercycle approach. The Al
<sub>x</sub>
Ni
<sub>y</sub>
O films showed a contact resistivity of 331 mΩ cm
<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>
with c-Si, in contrast to undoped NiO where no ohmic contact could be formed. This in-depth computational study followed by the experimental synthesis of Al
<sub>x</sub>
Ni
<sub>y</sub>
O films removes a critical barrier for the future applications of NiO-based carrier-selective passivating contacts for c-Si and other types of solar cells and provides a path for the optimization of other functional materials.
... 通 [7,8] . Gerling等 [6] [9] , 选取广义梯度近似(generalized gradient [10,11] . 平面波截断能选取530 eV, K点 网络选择Monkhorst-Pack方法. 在进行结构优化 时, 自洽收敛标准为：原子总能偏差小于10 -4 eV, 且原子间的Hellmann-Feynman力偏差小于0.02 eV/Å. ...
An amorphous mixing layer (3.5~4.0 nm) including silicon (Si), oxygen (O), molybdenum (Mo) atoms, named a-SiOx(Mo), is usually formed when evaporating molybdenum trioxide (MoO3) powder on the n-type Si substrate. In order to investigate the process of adsorption, diffusion and nucleation of MoO3 in the evaporation process and ascertain the formation mechanism of a-SiOx(Mo) at the atomic scale, the first principle calculation is used and all the results are calculated in the Vienna ab initio simulation package (VASP). The possible adsorption model of MoO3 on the Si (100) and the defect formation energy for substitutional and vacancy defects in α-SiO2 and α-MoO3 are calculated by the density functional theory. The results show that an amorphous layer is formed between MoO3 film and Si (100) substrate after ab initio molecular dynamics at 1500K, which is in good agreement with experimental observations. O and Mo atoms diffuse into Si substrate and form the bonds of Si-O or Si-O-Mo, and finally, cause the formation of a-SiOx(Mo) layer. The adsorption site 7 of MoO3 on the reconstructed Si (100) surface, which the two oxygen atoms of MoO3 bond with two silicon atoms of Si (100) surface, is the most stable and the adsorption energy is -5.36 eV, accompanied by the electrons transport from Si to O. After the adsorption of MoO3 on Si substrate, the structure of MoO3 is changed. Two Mo-O bond lengths of MoO3 are 1.95 Å and 1.94 Å separately, elongated 0.22 Å and 0.21 Å than before, while the last bond length of MoO3 is little changed. The defect formation energy of neutral oxygen vacancies in α-SiO2 is 5.11 eV and that of neutral oxygen vacancies in α-MoO3 are 0.96 eV, 1.96 eV and 3.19 eV, respectively. So it is easier to form oxygen vacancies in MoO3 than in SiO2, which implies that the oxygen atoms will migrate from MoO3 to SiO2 and forms the 3.5~4.0 nm a-SiOx(Mo) layer. As for substitutional defects in MoO3 and SiO2, Mo substitutional defects are most likely to form in SiO2 among a large range of Mo chemical potential. So based the result we obtained, the forming process of the amorphous mixing layer may be as follows: the O atoms from MoO3 bond with Si atoms at first and form the SiOx. Then, a part of Mo atoms is likely to replace Si atoms in SiOx. Finally, the ultra-thin buffer layer contained Si, O, Mo atoms is formed at the interface of MoO3/Si. This work simulates the reaction of MoO3/Si interface and makes clear the interfacial geometry. It is also good for us to further understand the process of adsorption and diffusion of atoms during evaporating. It provides a theoretical explanation for the experimental phenomenon and is beneficial for obtaining better interface passivation and high conversion efficiency of solar cell.
... The dipole nature of the α-MoO3 layers is at the origin of its relatively high work function (WF) of about 6.5 eV [1,5]. Moreover, despite its insulator nature and high WF, previous studies pointed out that thin MoO3 films may exhibit a conductive behavior in the presence of defects and oxygen vacancies [6][7][8][9][10] or via interaction with a metallic substrate such as copper [7]. ...
Structural changes of MoO3 thin films deposited on thick copper substrates upon annealing at different temperatures were investigated via ex situ X-Ray Absorption Spectroscopy (XAS). From the analysis of the X-ray Absorption Near-Edge Structure (XANES) pre-edge and Extended X-ray Absorption Fine Structure (EXAFS), we show the dynamics of the structural order and of the valence state. As-deposited films were mainly disordered, and ordering phenomena did not occur for annealing temperatures up to 300 °C. At ~350 °C, a dominant α-MoO3 crystalline phase started to emerge, and XAS spectra ruled out the formation of a molybdenum dioxide phase. A further increase of the annealing temperature to ~500 °C resulted in a complex phase transformation with a concurrent reduction of Mo6+ ions to Mo4+. These original results suggest the possibility of using MoO3 as a hard, protective, transparent, and conductive material in different technologies, such as accelerating copper-based devices, to reduce damage at high gradients.
... As for structure optimization, convergence tolerances were set to 10 −6 eV/atom for selfconsistent field energy cycle and 0.02 eV/Å was taken for the Hellmann-Feynman force. To describe the localization of d-electrons of molybdenum, an on-site Coulomb correction of 6.3 eV was used [15]. ...
An amorphous silica layer containing Mo component (a-SiOx(Mo) ∼ 3.5–4.0 nm) is naturally formed in the process of evaporating MoO3 power onto n-type silicon, which plays a significant role on the non-equilibrium carriers’ transport of MoOx/n-Si heterojunction photovoltaic device. The electronic structure and the charge transition levels of the amorphous silicon oxide doped with Mo are derived from density functional theory. The density of states show that the five local states are existed in the band gap of amorphous silicon oxide, caused by the hybridization of Mo 4d orbital and O 2p orbital. The charge transition level of ε(+1/0) is located at 3.59 eV above the valance band maximum of a-SiO2, which could be a passageway of holes produced in the opto-electric conversion. Defects level-assisted quantum transport mechanism is put forwarded to explain hole transport phenomenon in the MoOx/SiOx(Mo)/n-Si PV device.
Solid oxide fuel cells (SOFCs) are a key component of the future energy landscape. Although there is considerable research on the physical properties and technology of classic oxide materials for electrode and electrolytes in SOFCs, the field is very active as new experimental and theoretical techniques are now available that can improve these systems. In the present review, we consider key systems such as perovskite-related materials, the impact of strain and interfaces and advanced concepts that can improve the properties of SOFC materials. In particular, we consider the oxygen diffusion properties of perovskite-related materials and focus on La2NiO4+δ and the double perovskites such as GdBaCo2O5.5. Then, we review the importance of interfaces and strain as a way to engineer defect processes. Finally, we consider advanced concepts to form designed structures that explore the effect of local high entropy on lattice stabilization.
Molybdenum Oxide (MoO3) with van der Waals structure can lead to the exotic properties under the action of external physical perturbation. Here, a combined density functional theory and an experimental study were performed to analyze the response of MoO3 under electric field. The electric field with the strength varying from 0.05 V/Å to 0.23 V/Å was applied across the MoO3 cell which induced the splitting in the valence and conduction band and decreases the bandgap as predicted by the density functional theory. A critical electric field of 0.23 V/Å resulted a closing of the bandgap of MoO3 and led semiconductor to metal transition. The results of DFT regarding decrease in the bandgap of MoO3 were further supported experimentally. For this, MoO3 films were fabricated using thermal evaporation and their chemical and optical properties were analyzed using X-ray photoelectron spectroscopy and Electroreflectance (ER). To analyze the optical response, an ER analysis with external voltage varying from 10 to 50 volts was performed on Aluminum/MoO3/Aluminum heterostructure. The resultant ER spectra revealed three distinct critical points that correspond to the fundamental as well as defect related optical transitions involved in MoO3. The Third derivative functional form model applied on the ER spectra depicted a monotonical decrease in the critical points of MoO3 at lower voltage. At high voltage of about 80 volts, the existence of high built-in electric field results the delocalization in the electrons and hole wave function and gives rise to the Franz-Keldysh oscillations.
