Abstract:This work presents the implementation of ultrathin TiO2 films, deposited at room temperature by radio-frequency magnetron sputtering, as electron-selective contacts in silicon heterojunction solar cells. The effect of the working pressure on the properties of the TiO2 layers and its subsequent impact on the main parameters of the device are studied. The material characterization revealed an amorphous structure regardless of the working pressure; a rougher surface; and a blue shift in bandgap in the TiO2 layer … Show more
“…The efficiency of the homojunction silicon-based solar cell does not exceed 29% according to the Shockley–Quisser limit [ 22 ]. Therefore, various silicon-based heterojunction solar cells are being designed [ 23 ]. ZnO and perovskite materials coated on the silicon surface as an emitter layer have been found to increase their efficiency [ 24 ].…”
Metal oxides are commonly used in optoelectronic devices due to their transparency and excellent electrical conductivity. Based on its physical properties, each metal oxide serves as the foundation for a unique device. In this study, we opt to determine and assess the physical properties of MoO3 metal oxide. Accordingly, the optical and electronic parameters of MoO3 are evaluated using DFT (Density Functional Theory), and PBE and HSE06 functionals were mainly used in the calculation. It was found that the band structure of MoO3 calculated using PBE and HSE06 exhibited indirect semiconductor properties with the same line quality. Its band gap was 3.027 eV in HSE06 and 2.12 eV in PBE. Electrons and holes had effective masses and mobilities of 0.06673, −0.10084, 3811.11 cm2V−1s−1 and 1630.39 cm2V−1s−1, respectively. In addition, the simulation determined the dependence of the real and imaginary components of the complex refractive index and permittivity of MoO3 on the wavelength of light, and a value of 58 corresponds to the relative permittivity. MoO3 has a refractive index of between 1.5 and 3 in the visible spectrum, which can therefore be used as an anti-reflection layer for solar cells made from silicon. In addition, based on the semiconducting properties of MoO3, it was estimated that it could serve as an emitter layer for a solar cell containing silicon. In this work, we calculated the photoelectric parameters of the MoO3/Si heterojunction solar cell using Sentaurus TCAD (Technology Computing Aided Design). According to the obtained results, the efficiency of the MoO3/Si solar cell with a MoO3 layer thickness of 100 nm and a Si layer thickness of 9 nm is 8.8%, which is 1.24% greater than the efficiency of a homojunction silicon-based solar cell of the same size. The greatest short-circuit current for a MoO3/Si heterojunction solar cell was observed at a MoO3 layer thickness of 60 nm, which was determined by studying the dependency of the heterojunction short-circuit current on the thickness of the MoO3 layer.
“…The efficiency of the homojunction silicon-based solar cell does not exceed 29% according to the Shockley–Quisser limit [ 22 ]. Therefore, various silicon-based heterojunction solar cells are being designed [ 23 ]. ZnO and perovskite materials coated on the silicon surface as an emitter layer have been found to increase their efficiency [ 24 ].…”
Metal oxides are commonly used in optoelectronic devices due to their transparency and excellent electrical conductivity. Based on its physical properties, each metal oxide serves as the foundation for a unique device. In this study, we opt to determine and assess the physical properties of MoO3 metal oxide. Accordingly, the optical and electronic parameters of MoO3 are evaluated using DFT (Density Functional Theory), and PBE and HSE06 functionals were mainly used in the calculation. It was found that the band structure of MoO3 calculated using PBE and HSE06 exhibited indirect semiconductor properties with the same line quality. Its band gap was 3.027 eV in HSE06 and 2.12 eV in PBE. Electrons and holes had effective masses and mobilities of 0.06673, −0.10084, 3811.11 cm2V−1s−1 and 1630.39 cm2V−1s−1, respectively. In addition, the simulation determined the dependence of the real and imaginary components of the complex refractive index and permittivity of MoO3 on the wavelength of light, and a value of 58 corresponds to the relative permittivity. MoO3 has a refractive index of between 1.5 and 3 in the visible spectrum, which can therefore be used as an anti-reflection layer for solar cells made from silicon. In addition, based on the semiconducting properties of MoO3, it was estimated that it could serve as an emitter layer for a solar cell containing silicon. In this work, we calculated the photoelectric parameters of the MoO3/Si heterojunction solar cell using Sentaurus TCAD (Technology Computing Aided Design). According to the obtained results, the efficiency of the MoO3/Si solar cell with a MoO3 layer thickness of 100 nm and a Si layer thickness of 9 nm is 8.8%, which is 1.24% greater than the efficiency of a homojunction silicon-based solar cell of the same size. The greatest short-circuit current for a MoO3/Si heterojunction solar cell was observed at a MoO3 layer thickness of 60 nm, which was determined by studying the dependency of the heterojunction short-circuit current on the thickness of the MoO3 layer.
“…All of the films had an average transmission of around 80% in the visible spectrum. The Lambert–Beer law was used to calculate the optical absorption coefficients (α) as a function of the wavelength of the films, where T represents the transmittance% and t denotes the film thickness. The variation of the absorption coefficient follows Tauc’s relation α=2.303t(2−logT)…”
Section: Resultsmentioning
confidence: 99%
“…In this work, when all other parameters were kept fixed, only the sputtering gas pressure was varied, which caused significant changes in the films’ structural and optoelectronic properties. The sputtering pressure influenced the mean free path (λ) of the particles, following the relationλ=2.33×10−20Tpδm2where T is the temperature, p denotes the sputtering pressure, and m is the molecular diameter. , As a result, when the sputtering pressure rises, the reduced mean free path increases the frequency of collision of the sputtered Ti atoms with Ar and O atoms in the plasma, subsequently forming Ti–O bonds. These large numbers of collisions prevent the Ti and TiO moieties from reaching the substrate surface.…”
Section: Resultsmentioning
confidence: 99%
“…TiO 2 is a material possessing a wide variety of qualities, including excellent chemical inertness, superior photocatalytic activity, good optical transmittance with a high refractive index in the visible range, and strong mechanical hardness. − It is widely used in photoconversion-related issues, e.g., photodetectors, photocatalysis, and resistive switching devices, as a passivation layer in solar cell devices, high-K gate dielectric for the transistors, etc. − …”
Section: Introductionmentioning
confidence: 99%
“…where T is the temperature, p denotes the sputtering pressure, and m is the molecular diameter. 9,69 As a result, when the sputtering pressure rises, the reduced mean free path increases the frequency of collision of the sputtered Ti atoms with Ar and O atoms in the plasma, subsequently forming Ti−O bonds. These large numbers of collisions prevent the Ti and TiO moieties from reaching the substrate surface.…”
TiO 2 has the proven capability of catalytically decomposing pollutants under light illumination, thereby embracing potential applications in wastewater management. The photocatalytic dye degradation activity is largely controlled by the optical band gap that dictates the extent of electron− hole pair generation via photon absorption, and the recombination kinetics of charges. In this context, the material's work function governs how easily the charge carriers can be transferred at the dye-adsorbed photocatalytically active sites. Accordingly, nanocrystalline TiO 2 thin films are grown in the anatase phase with ⟨101⟩ orientation, using RF magnetron sputtering at 200 °C. Besides studying the film's structural morphology, optical band gap, and elemental composition, the electronic properties are extensively investigated. The work function of the material was controlled by varying the O-vacancydependent Ti 3+ bonding configuration in the network. It has been demonstrated how the photocatalytic methylene blue dye degradation activity of the nanocrystalline TiO 2 films of predominantly the anatase phase improves on reducing the sputtering pressure during deposition. At a low deposition pressure of 20 mTorr, a low work function of ∼4.2 eV of the film, resulting from the formation of a Ti 3+ -bond through the O vacancies in the network, potentially increases its carrier lifetime and delivers the superior photocatalytic activity (∼82.7% dye degradation with a rate constant of k ∼ 0.0073 min −1 ) via silently facilitating fast electron transfer from the photocatalyst to the dye in the aqueous solution. The higher stoichiometric film prepared at p = 40 mTorr exhibits an inferior photocatalytic activity (∼20.4% dye degradation with a rate constant of k ∼ 0.0009 min −1 ), as retarded by its higher work function of ∼4.62 eV, despite retaining a relatively low band gap. Thus, without using any heterojunction or extrinsically doped photocatalyst, the dye degradation can be controlled simply by reducing the work function of nanocrystalline TiO 2 thin films via controlling the O-vacancy-dependent Ti 3+ bonding in its self-doped network.
Molybdenum oxide (MoO3−x, x < 3) has been successfully used as an efficient hole‐selective contact material for crystalline silicon heterojunction solar cells. The carrier transport capability strongly depends on its work function, that is, oxygen vacancies; however, there are lack of effective methods to modulate the multiple oxidation states. Herein, the oxidation states of solution‐processed MoO3−x by doping Nb5+ to improve its hole‐selective contact performance with silicon are tuned. With the optimum doping concentration of 5%, both the reduced Mo5+ and oxygen vacancies increase, resulting in a decrease in the contact resistivity between the MoO3−x film and p‐type silicon from 161.1 to 62.9 mΩ·cm2 and an increase of the effective carrier lifetime from 165.4 to 391.0 μs simultaneously. Similarly, the doping of Ta5+ or V5+ in MoO3−x improves the passivated contact performance with silicon, while the former increases the concentration of oxygen vacancies and the latter reduces it. The solar cell with the structure of Ag/MoO3−x:Nb/p‐Si exhibits a conversion efficiency of 18.37%, which is the highest so far reported for the solution‐processed MoO3−x/silicon heterojunction. This work demonstrates a feasible strategy of tuning hole selectivity in MoO3−x by doping for high‐efficiency solar cells and other optoelectronic device applications.
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