Electron-hole Pair Generation Research Articles

Fundamentals of Circuit Failure Analysis Based on Optical Fault Isolation Techniques

Circuit failure analysis based on optical fault isolation (OFI) techniques is widely used for Si debugging at the early phase of product development or failure analysis to improve yield and reliability issues at mass production stage. Three of OFI techniques are usually used for failure analysis. Dynamic laser stimulation affects <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$V_{th}$ </tex-math></inline-formula> shift due to thermal heating or electron-hole pair generation in local area depending on the wavelength of the laser used. Laser voltage image and probing provide toggle image of signal and direct waveform differences between good and failure circuits, respectively. This paper introduces the fundamentals of Si level circuit analysis including digital and analog circuit using optical fault isolation method based on theoretical and experimental results.

Plasmonic enhancement of exciton and trion photoluminescence in 2D MoS2 decorated with Au nanorods: Impact of nonspherical shape

Two-dimensional (2D) MoS2 is emerging as a promising candidate for novel optoelectronics and flexible devices, but the photoluminescence (PL) efficiency is still limited for actual photonic applications. Plasmonic enhancement is the best way to increase the PL emission of 2D materials. In this study, the PL enhancement of 2D MoS2 decorated with Au nanorods (NRs) and nanospheres (NSs) at room temperature is investigated, focusing in particular on the effect of the nonspherical shape of NRs. To have a proper comparison, both nanoparticles have very similar diameters of 13–14 nm, while the NR average length is 81 nm. After decorating with Au NRs and NSs, the average PL enhancement of few-layer MoS2 is about 4.3 and 2 times, respectively. The Raman spectra are similarly enhanced, 3.8 and 2.4 times (A1g mode), respectively. The maximal enhancement is observed for the samples with Au NRs: this feature can be related to highly localized plasmonic hot spots in vicinity of the NR tips. A strong electric field within the hot spots causes the generation of additional free electron-hole pairs and, in turn, the enhancement of exciton excitation and the increase of the PL intensity. Simultaneously, the injection of hot electrons from the metal increases the probability of trions generation, thus contributing to the PL enhancement.

Optimization ZnO Properties for Electron Transport Layer (ETL) of Hybrid Solar-cell Prepared with Sol-gel Method Combined with Reflux Treatment

Electron-hole pair (exciton) generation and extraction from solar-cell photoactive layer is the main parameters determined solar-cell performance. Generally solar-cell consists of a photoactive layer sandwiched between electron transport layer (ETL) and hole transport layer (HTL). Exciton separation and extraction from photoactive layer depend on several properties: energy level match of photoactive layer and charge transport layer, surface contact area of photoactive layer and charge transport layer, and charge transport properties of charge transport layer. ETL and HTL should meet several characteristic e.g.: high transparency in UV-visible light region, high degree of crystallization to minimize charge lose and high electron or hole mobility. In this study we try to fabricate ZnO as an ETL of hybrid solar-cell with sol-gel method combined with reflux treatment. The quality of ZnO ETL highly effected by precursor solution properties; solution homogeneity, viscosity and stability. These precursor solution properties depend on chemical composition and reaction condition, reflux treatment designed to enhance precursor solution reaction time and increase solution stability. Previous study shown low solution stability of ZnO precursor prepared with sol-gel without reflux treatment which resulting on low ETL quality. Visible observation of the resulting precursor solution showed that reflux treatment enhances solution stability, while solution prepared without reflux treatment easily formed precipitation phase. Furthermore, ZnO powder prepared with reflux treatment exhibit preferable crystallization and small ZnO crystallite size. Low-temperature crystallization of ZnO prepared with sol-gel method combined with reflux treatment, make it is possible to fabricate thin film with small particle size therefore able to enhance surface contact area of photoactive layer and ETL.

A Heterostructured Graphene Quantum Dots/β-Ga2O3 Solar-Blind Photodetector with Enhanced Photoresponsivity.

The superior optical and electronic characteristics of quasi-two-dimensional β-Ga2O3 make it suitable for solar-blind (200-280 nm) photodetectors (PDs). The metal-semiconductor-metal (MSM) PDs commonly suffer from low photoresponsivity, slow response speed, and a narrow detection wavelength range despite their simple fabrication process. Herein, we report a high-performance MSM PD by integrating exfoliated β-Ga2O3 flakes with zero-dimensional graphene quantum dots (GQDs), which exhibits the advantages of enhancing the photoresponsivity, shortening the photoresponse time, and stimulating a broad range of photon detection. The hybrid GQDs/β-Ga2O3 heterostructure PD is sensitive to deep-ultraviolet (DUV) light (250 nm) with an ultrahigh responsivity (R of ∼2.4 × 105 A/W), a large detectivity (D* of ∼4.3 × 1013 Jones), an excellent external quantum efficiency (EQE of ∼1.2 × 108%), and a fast photoresponse (150 ms), which is superior to the bare β-Ga2O3 PD. These improvements result from effective charge transfer due to the introduction of GQDs, which enhance the light absorption and the generation of electron-hole pairs. In addition, the hybrid GQDs/β-Ga2O3 PD also exhibits better photoelectric performance than the bare β-Ga2O3 PD at a 1000 nm wavelength. As a conclusion, the hybrid GQDs/β-Ga2O3 DUV photodetector shows potential applications in commercial optoelectronic products and provides an alternative solution for the design and preparation of high-performance photodetectors.

Photocatalytic study of metal oxide enhanced ZnO synthesized by a one-step cyclic-microwave method: The role of the p-n heterostructure

In this work, the role of the p-n junction in the photocatalytic degradation of various dyes in contaminated wastewater was studied. The n-type ZnO was synthesized by the cyclic-microwave method and was enhanced by various metal oxides, e.g., CuO, NiO, and Fe2O3. The materials were characterized by various methods. The degradation of Methylene blue (MB), Methyl orange (MO), and Rhodamine B (RhB) under the photocatalysts and UV light irradiation was examined. From the results, the performance of the dye degradation by the p-n CuO/ZnO and NiO/ZnO materials was better than that of the pure ZnO. On the other hand, the n-n heterostructure Fe2O3/ZnO showed a decrease in photocatalytic performance. The photocatalyst with the highest performance was Ni(5)-ZnO, which can degrade dyes contaminating water by greater than 99.71%. The physical principle behind the increase in the photocatalytic performance is due to the formation of the p-n junction by CuO and NiO to the n-type ZnO, resulting in the efficient generation of electron-hole pairs.

Perspectives on composite films of chitosan-based natural products (Ginger, Curcumin, and Cinnamon) as biomaterials for wound dressing

Natural materials are gaining popularity in wound healing and food applications, and they have the potential to alleviate the major environmental problems generated via traditional materials. Biomaterials based on Chitosan incorporated with natural products (Ginger, Curcumin, and Cinnamon) have been fabricated by solvent casting method. The antimicrobial characterization of the prepared samples were also investigated using in vitro antimicrobial studies using Gram-positive microorganism [ Micrococcus luteus , Staphylococcus aureus , and Staphylococcus epidermidis ], Gram-negative microorganism [ Pseudomonas aeruginosa ], and pathogenic [ Candida albicans ]. XRD patterns confirmed the complexation between chitosan and other natural products and this indicate the change in structural of chitosan. The shifting and disappearing of bands in FTIR-ATR and changing in fingerprints in FTIR spectra indicate the homogeneity and interaction between chitosan and the other. Optical properties such as absorption, absorption coefficient, Urbach tail and band gap calculation confirmed that Ginger, Curcumin and Cinnamon interact with chitosan and induces localized state between valence and conduction band. The mechanical properties also studied and revealed that Chitosan/Ginger has the best mechanical characteristic compared the other samples. In addition, the shifting toward higher wavelength for chitosan/Ginger may be utilized to generate electron–hole pairs, which is important for antimicrobial activities, and this confirmed from antimicrobial analysis that Chitosan/Ginger give high antimicrobial activity toward Gram-positive microorganism and suggest it for wound dressing application.

Photovoltaic effect by soft phonon excitation

SignificanceThe quantum-mechanical geometric phase of electrons provides various phenomena such as the dissipationless photocurrent generation through the shift current mechanism. So far, the photocurrent generations are limited to above or near the band-gap photon energy, which contradicts the increasing demand of the low-energy photonic functionality. We demonstrate the photocurrent through the optical phonon excitations in ferroelectric BaTiO3 by using the terahertz light with photon energy far below the band gap. This photocurrent without electron-hole pair generation is never explained by the semiclassical treatment of electrons and only arises from the quantum-mechanical geometric phase. The observed photon-to-current conversion efficiency is as large as that for electronic excitation, which can be well accounted for by newly developed theoretical formulation of shift current.

First principles approach to solar energy conversion efficiency of semiconductor heterojunctions

We present an approach to determine from first principles the expected efficiency of semiconductors heterojunctions in solar light absorption and electron-hole pairs generation for photocatalysis and solar cells applications. In a composite material, upon absorption of photons of appropriate wavelength, electrons and holes can migrate towards different components of the junction, thus reducing the electron-hole recombination probability. This occurs when the bands of the two semiconductors are properly aligned. However, a favorable band alignment is not a sufficient condition to have a device able to convert efficiently solar light into chemical or electrical energy. Using the Transfer Matrix Method and Density Functional Theory calculations we evaluate the transmittance and reflectivity of the charge carriers, and we determine two descriptors, the injection efficiency and the maximum conversion efficiency, that allow us to predict in a more realistic way the performance of the device. This method is based on the explicit inclusion of surface, interface, and quantum confinement effects that can be present when the heterojunction is formed. By using the YP/TiO2 (Y = Al, Ga, In) and the CsPbX3/TiO2 (X = Cl, Br, I) systems as examples we show that the approach provides an excellent agreement with the available experimental data.

Polarization-dependent conversion efficiency of carbon nanotube-Si heterojunction solar cells based on aligned carbon nanotube films

We have fabricated solar cells that implement heterojunctions of Si and aligned carbon nanotube (CNT) films. Polarization-dependent optical absorption of highly aligned CNTs led to polarization-dependent conversion efficiencies, which in turn provided insight into the role of the CNT layer in the power generation mechanism in these heterojunction solar cells. When the incident light polarization was parallel to the CNT alignment direction so that the light absorption in the CNT layer was maximized, the short circuit photocurrent decreased by ∼25%. This indicates that electron–hole pair generation in the CNT layer does not directly lead to power generation and that the CNT-Si heterojunctions in our devices are Schottky junctions rather than p–n junctions.

Non-adiabatic quantum dynamics of tribovoltaic effects at sliding metal–semiconductor interfaces

Recent experiments observe electric current generation at sliding metal–semiconductor interfaces. Here, we present a detailed theoretical study on how electric voltage is generated at such a sliding interface. Our study is based on a two-band Anderson–Holstein model, where we solve the coupled electron–phonon dynamics using a surface hopping method. We show that the high local temperature induced by mechanical motion at the interfaces can lead to electron–hole pair generation through electron–phonon couplings. We quantify the efficiency of electron–hole generation as well as electric voltage as a function of local temperatures and semiconductor bandgaps. We find that increasing the local temperatures can lead to higher electron–hole generation and electric voltage. Furthermore, we find that there is a turnover for the electric voltage as a function of the bandgap. Such an observation is in agreement with the experimental results. Our study offers a theoretical framework to understand tribovoltaic effects from a quantum mechanical point of view, and our approach can be used to quantitatively simulate realistic sliding metal–semiconductor junctions.

Promoting Spatial Charge Transfer of ZrO2 Nanoparticles: Embedded on Layered MoS2/g-C3N4 Nanocomposites for Visible-Light-Induced Photocatalytic Removal of Tetracycline.

Photocatalytic degradation is a sustainable technique for reducing the environmental hazards created by the overuse of antibiotics in the food and pharmaceutical industries. Herein, a layer of MoS2/g-C3N4 nanocomposite is introduced to zirconium oxide (ZrO2) nanoparticles to form a “particle-embedded-layered” structure. Thus, a narrow band gap (2.8 eV) starts developing, deliberated as a core photodegradation component. Under optimization, a high photocatalytic activity of 20 mg/L TC at pH 3 with ZrO2@MoS2/g-C3N4 nanocomposite was achieved with 94.8% photocatalytic degradation in 90 min. A photocatalytic degradation rate constant of 0.0230 min–1 is determined, which is 2.3 times greater than the rate constant for bare ZrO2 NPs. The superior photocatalytic activity of ZrO2@MoS2/g-C3N4 is due to the dual charge-transfer channel between the MoS2/g-C3N4 and ZrO2 nanoparticles, which promotes the formation of photogenerated e–/h+ pairs. Charge recombination produces many free electron–hole pairs, which aid photocatalyst reactions by producing superoxide and hydroxyl radicals via electron–hole pair generation. The possible mechanistic routes for TC were investigated in-depth, as pointed out by the liquid chromatography–mass spectrometry (LC–MS) investigation. Overall, this work shows that photocatalysis is a feasible sorbent approach for environmental antibiotic wastewater treatment.

Analysis of Spectral Transmission in Si Solar Cell with Pyramidal Texturization by Using PC3S Simulation

Management of light is a crucial task in solar cell design and structure because it increases the path length of the light inside, which in turn increases the probability of electron-hole pair generation. This study addresses the impact of a pyramidal textured structure on spectral transmission in the morphology of silicon. The morphology of silicon wafers was investigated using PC3S spectral transmission software to study the spectral transmission, reflectance, collection probability, mobility, carriers, electric field, velocity, current and surface recombination. Spectral transmission on the front surface with pyramidal texture showed a better transmission percentage than the planar surface. The texture with a depth of 20 μm and base length of 20 μm exhibited good performance in front spectral transmission, spectral reflectance, electric field, velocity, current and surface recombination from the top to the bottom of the sample. The planar surface had more reflectance and lower collection probability than the other pyramidal textured samples due to its low mobility, carriers, electric field, velocity and current but high surface recombination.

Synthesis, characterization, and photocatalytic activity of ZnO nanostructures

This study investigated the synthesis, characterization of ZnO nanostructures using different precipitating agents in the photodegradation of rhodamine B (Rh B) using scanning electron microscopy (SEM), X-ray diffraction (XRD), fourier transform infrared (FTIR) and UV/Vis spectroscopy and zeta potential measurements. The results indicated the dependence of morphology on calcination temperature and the precipitating agent. The colloidal stability of these nanomaterials is affected with the morphology changed. The photocatalytic results showed that ZnO nanostructures synthesized with NH4OH (98.98%) were more efficient in the degradation of Rh B than ZnO nanostructures synthesized with NaOH (62.68%). This is related to ZnO (NH4OH) nanoparticles should present a higher density of electronic defects than ZnO (NaOH), producing energy levels between the band gaps. These results are potentially associated with a combination of optical and geometric factors that create other paths for the generation of electron-hole pairs in the precipitated ZnO nanocatalyst with different alkaline solutions.

Investigations of Fused Deposition Modeling for Perovskite Active Solar Cells.

The advent of Fused Deposition Modeling (FDM; or 3D printing) has significantly changed the way many products are designed and built. It has even opened opportunities to fabricate new products on-site and on-demand. In addition, parallel efforts that introduce new materials into the FDM process have seen great advances as well. New additives have been demonstrably utilized to achieve thermal, electrical, and structural property improvements. This combination of fabrication flexibility and material additives make FDM an ideal candidate for investigation of perovskite materials in new solar cell efforts. In this work, we fabricate and characterize a perovskite-based solar cell polymer designed for the FDM fabrication processes. Perovskite solar cells have garnered major research interest since their discovery in 2009. Perovskites, specifically methylammonium lead iodide, offer beneficial properties to solar cell fabrication such as long minority charge carrier distance, high light absorption, and simple fabrication methods. Despite the great potential of these materials, however, stability remains an issue in solar cell utilization as the material degrades under ultraviolet light, exposure to oxygen and water, as well as increased temperatures. To mitigate degradation, different fabrication methods have been utilized. Additionally, multiple groups have utilized encapsulation methods post-fabrication and in situ solution processed integration of polymer materials into the solar cell to prevent degradation. In this paper, we leverage the unique ability of FDM to encapsulate perovskite materials and yield a MAPbI3-PCL solar material as the active layer for solar cell use. In this manner, increased ability to resist UV light degradation and material stability from other environmental factors can be achieved. This study provides characterization of the material via multiple techniques like SEM (Scanning Electron Microscopy) and XRD (X-ray Diffraction) as well as absorbance, transmittance, and photocurrent response. Investigations of processing on perovskite degradation as well as initial solar simulated response are recorded. Unique aspects of the resulting material and process are noted including improved performance with increased operating temperature. Increased electron–hole pair generation is observed for 200 m FDM-printed PCL film, achieving a 45% reduction in resistance under peak incident flux of 590 W/m with the addition of MAPbl3. This work establishes insight into the use of FDM for full solar cell fabrication and points to the next steps of research and development in this growing field.

Unidirectional coupling and efficient detection of near-infrared surface plasmon polaritons for on-chip optoelectronic interconnection.

Plasmonic interconnection is one kind of the possible methods to construct next-generation optoelectronic integrated circuits. In this paper, the plasmonic interconnection device based on Ge in infrared band is constructed, through efficient electron-hole pair generation, the device can achieve high photocurrent response (0.25A/W). Because of the low plasmon coupling efficiency of the conventional basic periodic gratings, this paper optimized the design of the coupling structure and improved the coupling efficiency by 4 times through constructing a binary Bragg/periodic grating coupler which can realize unidirectional plasmon coupling with a simulated extinction ratio of 12.5 dB. The devices can be easily fabricated by single-step electron beam lithography and lift-off process. The experimental results verified a 3.5 times improvement in the SPPs current of the designed plasmonic interconnection device, which provides a technical path to realize efficient plasmon transmission and detection for on-chip optoelectronic interconnection.

In-situ sunlight-driven tuning of photo-induced electron-hole generation and separation rates in bismuth oxychlorobromide for highly efficient water decontamination under visible light irradiation

Photocatalytic materials have received great interest due to their capability for remediating environmental pollution especially water pollution. However, the scalable application of the current photocatalytic materials is still limited by their poor visible-light absorption and low separation efficiency of charge carriers. Here, we report in-situ sunlight-driven tuning of photo-induced electron-hole generation and separation rates in bismuth oxychlorobromide (BiOCl0.8Br0.2) nanoflowers. It shows photochromic response under 10-minute natural sunlight irradiation changing color from white to black. The characterization reveals the presence of hydroxyl groups on the surface of the pristine BiOCl0.8Br0.2 nanoflowers and abundant oxygen vacancies for the sunlight-irradiated BiOCl0.8Br0.2 nanoflowers which narrow the bandgap and serve as electron trapping centers, thus effectively enhancing the generation and separation rates of electron-hole pairs. As a result, the sunlight-irradiated BiOCl0.8Br0.2 film demonstrates outstanding photocatalytic performance in water purification such as degrading Rhodamine B (RhB) dye under visible light irradiation with 2-fold higher than its pristine state.

Sol-gel technique in study of titanium dioxide (TiO2) photocatalytic activity- a short review

Many treatment methods are available for wastewater treatment, but they are unable to remove completely the dyes and pigments from the wastewater. Some of the wastewater treatment methods depend on the formation of secondary pollutants and these methods are not suitable and applicable methods for preserving the environment. Photocatalytic is a superb and economical process to solve this problem. In this paper, a review of photocatalytic activity will be discussed. Photocatalytic is the process occurring when a light source incident on the surface of materials especially in semiconductors, known as photocatalysts. The paper began with a discussion on the sol-gel technique that shows it is an effective method to obtain straightforward processing, low cost and eco-friendly. Factors such as temperature and type of dopants gave an effect on the photocatalytic process. The temperature could help change the physical and chemical properties of the material. Besides, by using the sol-gel method, high purity and small particle size can be produced by controlling the calcination temperature titanium dioxide (TiO2) has widely used in the photocatalytic process where nitrogen (N) and magnesium (Mg) act as dopants. Magnesium is one of the abundant alkaline earth metals and is less hazardous to be used in the water treatment process which will cause a more environmentally friendly process. In addition, the band gap of TiO2 can be narrowed by introducing metal and non-metal ions into TiO2. Dopants increase the generation of free electron-hole pairs and the conductivity rate of materials. Besides that, the heterogeneous catalytic process's kinetics can be studied using the Theory of Langmuir-Hinshelwood. This theory explains the mechanism of reactions on the surfaces when more than oneadsorptioninvolves. Reactions between solid and gas at the interface were related to the catalysis process. Further, the application of doped TiO2 has also been discussed to emphasize the importance of photocatalytic for all fields.

Determination of the types of optical transitions and concentrations of donors and acceptors in GaN by the dependence of photoluminescence intensity on the excitation power

The results of the calculated and experimental depen-dence of the photoluminescence intensity on the excitation power density for silicon-doped GaN layers grown by molecular beam epitaxy are presented. A model was constructed for transitions in a compensated semiconductor upon interband generation of electron-hole pairs. It is shown that the dependence of the photoluminescence intensity on the excitation power density can be used to determine the recombination mechanism and concentrations of donors and acceptors in semiconductor. Keywords: GaN, ammonia-MBE, photoluminescence, heterostructures, point defects.

RADIATIVE AND MAGNETICALLY STIMULATED CHANGE OF THE ELECTRICAL PROPERTIES OF THE SiO2-Si STRUCTURE WITH A HIGH CONTENT OF DISLOCATION COMPLEXES

The effect of various types of irradiation and magnetic field on the surface of the semiconductor is a relevant topic, since it is the change in the density of the SS that is responsible for the occurrence of sensitive (sensory) effects associated with dislocations adsorbed particles. The paper examines the effect of X-irradiation on the Si surface with different dislocation density (10 2 – 10 5 cm -2 ). The capacitance–voltage characteristics (CVC) of the Bi-SiO 2 -Si-Al structure indicate (their maxima) a sufficiently large charge in the dielectric layer of the capacity of this maximum. As the dislocation density increases, the capacitance value in the region of positive voltages decreases, which is associated with a decrease in the spatial charge region (SCR) value, as well as the distribution of the density of surface states in the band gap and their rate of recharging changes. To determine the density of surface states, the ideal (mathematically calculated) structures of Bi-SiO 2 -Si-Al (MOS) is compared with the real one. It is shown that the maximum concentration of SS is formed in the defect layers of the transition region, in which there are maximum mechanical stresses. The source of such stresses can be dislocations, which contribute to the energy spectrum of the surface. They increase the concentration of surface states in the depicted silicon zone by an order of magnitude. The spectrum becomes more complex with well-defined maxima in the energy range [from -0.1 to +0.4] eV at N ~ 10 5 cm -2 . This is due to the fact that, with low-energy irradiation of barrier structures in silicon oxide, the process of generation of electron-hole pairs occurs. The mobility of electrons in SiO 2 is much higher than the mobility of holes. Electrons that do not recombine leave the dielectric, holes (p + ) thermalize and fall to levels near the ceiling of the valence band. Thermal excitation of holes causes their capture at the level of tight bonds with a disturbance of equilibrium and the movement of atoms from the local to the free energy minimum. At the same time, the reaction takes place: ≡Si-O-Si≡ + p + →Si + +O 0 -Si≡ it shows the formation of "trivalent" silicon and "non-bridging" oxygen, which lead to the emergence of pseudovacancies, which lead to the accumulation of an additional charge in SiO 2 when the silicon structure is irradiated. In this case, the increase in the dislocation density enhances the effect of the radiation-stimulated SS change at the SiO 2 -Si interface. Under the action of X-irradiation on the surface of Si, there is a rearrangement of existing metastable defects and the formation of new ones, the increase in the density of which is associated with heterogeneity them from the volume semiconductor to the surface. They make a significant contribution to the SS spectrum. Upon irradiation, they can reorganize into more complex complexes with a change in SS. As a result of aging the structure Bi-SiO 2 -Si-Al in a magnetic field (MF) (B = 0.17 T) with different dislocation concentrations (terms of 4, 12, 20 days), the SS spectrum changes significantly. At N ≈ 10 4 – 10 5 cm -2 becomes monotonous after 20 days. The effect of a magnetic field on silicon does not cause the generation of electrically active defects in the near-surface layers of semiconductor, but promotes the rearrangement of oxygen and hydrogen complexes adsorbed on the surface, which are present on Si. It is they who determine the nature of the change in the SS due to the actions of the MF. Under the action of a magnetic field, a spin-dependent process of breaking chemical bonds in nanoclusters of structural defects (Si-H, Si-OH, -OH) occurs. As a result of breaking chemical bonds, hydrogen ions diffuse across the crystal and passivate acceptor and donor bonds. In addition, the action of MF leads to dynamic polarization of the nuclei of the Si 29 isotope atom and polarization of the electron spins in Si to the electron spins of oxygen due to the ultrathin interaction with polarized nuclei. A change in the orientation of the electron spin leads to the breakdown of the chemical bond. The effect of MF detection on non-magnetic materials, which are non-magnetic, is enhanced by prolonged exposure of samples to MF and the presence of defects in the near-surface layers. It is obvious that the presence of a dislocation will strengthen the influence of the MF on the change of the SS at the boundary SiO 2 -Si. Key words : silicon, magnetic field, X-irradiation, dislocations.

Performance Evaluation of an Improved Double Intrinsic Layer CdTe/a-Si Thin Film Photovoltaic Cell

This paper presents a 1μm×1.25μm×1μm heterojunction thin film photovoltaic cell having “p-i1-i2-n” cell structure. The designed “ITO/p-CdTe/i1-CdTe/i2-a-Si/n-a-Si/ITO” photovoltaic cell is investigated, optimized and simulated in Silvaco TCAD. Finite Element Analysis (FEA) has been carried out to cater all physical and numerical models to generate practical results. For improvement in cell efficiency, a 1.52 eV wide-bandgap p-layer of CdTe is used which specifically improves the short circuit current (JSC). JSC is directly involved in the improvement of conversion efficiency. For the active region, an intrinsic CdTe layer is combined with an intrinsic amorphous silicon (a-Si) layer. This combination of intrinsic layers in active region is responsible for maximum absorption of photons with a wide range of energies and results in additional electron hole pair generation. Selective absorption is used to maximize light trapping and strong scattering of incident light into active region. Indium Tin Oxide (ITO) is used as front layer and back contact layer with Aluminum (Al) because it offers low resistivity of ~10-4 Ωcm and a transmittance of greater than 90%. Results have been validated by implementing two reported cells with p-i-i-n and p-i-n structures. The results indicate achievement of 28.05% conversion efficiency of the proposed heterojunction cell. The achieved efficiency is better than the efficiencies of the related cells compared in this work and also higher than that of the 25.6% of conventional Heterojunction Intrinsic Thin-film (HIT) silicon solar cells.