P-type Silicon Research Articles

Creation of Flexible Heterogeneously-Doped Carbon Nanotube Paper PN Diodes to Enhance Thermoelectric and Photovoltaic Effects

This study investigates the fabrication and characterization of flexible PN diode devices using phosphorus- and boron-doped carbon nanotube (CNT) paper, also known as Buckypaper (BP). The BP substrate is fabricated from multi-walled carbon nanotubes (MWCNTs) and doped with phosphorus and boron to form N-type and P-type semiconductors, respectively. Various experimental techniques, including Raman spectroscopy, Hall effect measurements, and scanning electron microscopy (SEM), are employed to analyze the properties of the doped BP. The results reveal that the current-voltage (I-V) and capacitance-voltage (C-V) characteristics preliminarily exhibit the basic electrical properties of a diode after doping with P-type and N-type carriers. Subsequently, optimized vertical stacking combined with parallel electrode configurations for the BP diode devices demonstrates that vertical series stacking gradually enhances the thermoelectric voltage, while horizontal parallel connections approximately scale up the thermoelectric and photovoltaic voltages proportionally. The findings underscore the critical role of creating heterogeneously doped CNT-paper PN junction electric fields in improving the performance of carbon-based semiconductor devices. Furthermore, we demonstrate that these directionally oriented energy devices, when stacked, can form modular systems with enhanced efficiency. This work highlights the potential of flexible carbon material-based devices for advanced thermoelectric and photovoltaic applications.

Is p-Type Doping in TeO2 Feasible?

Abstract Wide-bandgap two-dimensional (2D) β-TeO2 has been reported as a high-mobility p-type transparent semiconductor (Nat. Electron. 2021, 4, 277-283), attracting significant attention. This “breakthrough” not only challenges the conventional characterization of TeO2 as an insulator but also conflicts with the anticipated difficulty in hole doping of TeO2 by established chemical trends. Notably, the reported Fermi level of 0.9 eV above the valence band maximum actually suggests that the material is an insulator, contradicting the high hole density obtained by Hall effect measurement. Furthermore, the detected residual Se and the possible reduced elemental Te in the 2D β-TeO2 samples introduces complexity, considering that elemental Se, Te, and Te1-x Se x themselves are high-mobility p-type semiconductors. Therefore, doubts regarding the true cause of the p-type conductivity observed in the 2D β-TeO2 samples arise. In this Letter, we employ density functional theory calculations to illustrate that TeO2, whether in its bulk forms of α-, β-, or γ-TeO2, or in the 2D β-TeO2 nanosheets, inherently exhibits insulating properties and poses challenges in carrier doping due to its shallow conduction band minimum and deep valence band maximum. Our findings shed light on the insulating properties and doping difficulty of TeO2, contrasting with the claimed p-type conductivity in the 2D β-TeO2 samples, prompting inquiries into the true origin of the p-type conductivity.

Light- and Elevated Temperature-Induced Degradation and Recovery from Silicon Wafers by the Impact of Hydrogen Treatment

Abstract Light- and elevated-temperature-induced degradation (LeTID) affects materials used in solar cell fabrication, especially gallium- and boron-doped p-type, and various n-type silicon wafers. Dark annealing at elevated temperatures promotes hydrogen diffusion into the bulk of silicon wafers. Here, dark-annealing was consistently performed at 200°C for 15 minutes to observe its impact on degradation and recovery. Higher temperatures accelerated LeTID, necessitating rapid annealing for regeneration. The chosen temperature range (75, 120, and 135°C) was selected to simulate real-world solar panel operating conditions and to observe degradation under both moderate and extreme temperatures. Forming-gas annealing increased the carrier lifetime of boron-doped silicon wafers by up to 92.8% and gallium-doped wafers by up to 16.3% from their initial values after degradation. Dark-annealing resulted in 40% and 28% increases in the carrier lifetimes of fully degraded gallium- and boron-doped silicon wafers, respectively. The proposed model explains the behavior related to different diffusivities of hydrogen in gallium- and boron-doped silicon wafers during dark-annealing. The LeTID mechanism involves three stages: generating inactive recombination centers (Di) and H+ ions during manufacturing, converting Di to HDi+1, enhancing carrier recombination, and, during regeneration, the injection of carriers (e-) transitions to a recombination inactive state.

N- to p-Type Conductivity Transition of Lu3N@C80 Due to Anisotropic Deformation of Fullerene and Pyramidalization of Endohedral Clusters.

The endohedral fullerene Lu3N@C80 was examined using in situ high-pressure measurements, which included electrical transport, Fourier-transform infrared spectroscopy, and Raman spectroscopy, in combination with theoretical calculations. Lu3N@C80 was found to undergo a reversible n- to p-type conversion at ∼8.9 GPa. This p-type semiconductor remains stable up to 25 GPa. The fullerene cage collapses at ∼29 GPa, resulting in an irreversible p- to n-type conversion. Raman, infrared, and X-ray absorption spectroscopy reveal that an anisotropic distortion of the carbon cage and a pyramidalization of the planar Lu3N clusters occur during compression. Density functional theory simulations indicate that the p orbitals of C atoms in the fullerene cage primarily contribute to the density of states (DOS). Pressure-induced deformation of the fullerene cage dominates the DOS changes in the conduction and valence bands close to the Fermi level. The findings elucidate the relationship between the conductivity and structural changes in the endohedral clusters.

Synthesis of CdTe microstructures on p-type silicon (111) using light-modulated electrodeposition

In this paper, we present the results of our electrodeposition experiments of cadmium telluride (CdTe) microstructures on p-type silicon (111) spatially modulated by the incidence of light. This technique has shown itself to be practical and inexpensive, with immediate results. The construction from an adequate microcell to the process and all the required methodologies by such a technique are also shown. Photoelectrodeposition allows the creation of localized microdeposits, since the type of substrate used is activated locally by focalized light incidence. The photoelectrodeposited samples were characterized by optical profilometry and scanning electron microscope (SEM). The profilometry analyses showed that the deposit dimensions are directly proportional to the incident laser power but are not significantly influenced by the exposure time. The SEM has revealed information regarding the size and the concentration of the clusters on the deposited regions. The size of these agglomerates is affected by the laser intensity, showing itself higher on the center of the deposits than on the peripheral regions. Both the size of the clusters and their concentrations increase as the laser exposure time increases. Furthermore, higher concentrations of clusters are seen when linear polarization is used instead of circular polarization, but circular polarization generates larger clusters.

Electrochemical performance of Li-ion battery-based porous silicon nanowires (PSiNWs) decorated with silver nanoparticles

ABSTRACT In recent years, silicon-based materials have attracted great interest for their use as anode in lithium-ion batteries due to their low charging potential and high specific capacity. Morever, silicon nanowires (SiNWs) have been shown to successfully solve the volume-expansion problem by providing free volumes to accommodate silicon expansion. In this work, we fabricated porous silicon nanowires (PSiNWs) on an n-type silicon wafer using a single low-cost metal-assisted chemical etching (MACE) step. Then, the formed (PSiNWs) nanowires were extracted and covered with silver nanoparticles. To reveal the underlying physical and electrochemical mechanisms, we also process a sample of comparative porous silicon nanowires, ranging in diameter from 50 to 100 nm and having a porosity of approximately 60%. The specific capacity is approximately 3635 mA h g−1 with a Coulomb efficiency of 98.8% in the first charge/discharge cycle for PSiNWs/AgNPs, while PSiNWs exhibit low capacity during the first cycle. This study highlights the design of porous silicon nanowires with a large specific surface area and the structural modification of the surface with silver nanoparticles.

Insights into the Synthesis of a Semiconducting Nickel Bis(dithiolene) Coordination Polymer.

Nickel bis(dithiolene) complexes are promising candidates for novel n-type semiconductors, which are air-stable and highly conductive. A key issue for further development is that their synthesis often yields undesired products, greatly limiting the degree of polymerization as well as purity and adversely affecting their electronic properties. Crucially, there is a lack of in-depth identification of these species and understanding of the reaction mechanism. This study explores the mechanism of a reaction forming the coordination polymer nickel-thieno[3,2-b]thiophenetetrathiolate (Ni-TT). We find that the Unoxidized Ni-TT intermediate contains negatively charged polymer chains with Ni2+ counter cations. Oxidation in the final synthetic step occurs primarily at the ligand, resulting in a more neutral Ni-TT. Our investigation also reveals that the ligand can form dimeric and trimeric species via disulfide bonds as byproducts. These insights are pivotal knowledge to develop metal bis(dithiolene)-based coordination polymers to achieve purity and quality required for electronic applications.

Electronic Nature and Thermoelectric Characteristics of Cubic LaPb3 LaIn3 and LaTl3 Compounds: B3PW91 Approach

In this paper the structural, electronic and transport properties of the strongly correlated intermetallics LaX3 (X=Pb, In and Tl) in the space group Pm-3m (221) have been investigated using B3PW91 hybrid functional within the framework of density functional theory. These compounds have 4f orbitals and hence strong electron-electron correlation effect is expected, therefore, the electronic properties are also calculated with the B3PW91 hybrid functional and the effect of B3PW91 hybrid functional on the density of states is discussed in details. The band structure and density of states, demonstrate the metallic nature of these compounds. Using the semi-empirical Boltzmann’s approach implemented in the BoltzTraP code, the transport parameters, such as the Seebeck coefficient, electrical conductivity, thermal conductivity and figure of merit as a function of the chemical potential are computed at a temperature gradient of 500 K. For all materials the thermal and electrical conductivities, and Seebeck coefficient has higher values for n-type doping in comparison with p-type doping. The moderate values of figure of merit obtained for these materials indicate that these materials have applicability where small values of thermoelectric efficiency are required and higher values can harm the process but need experimental verification. LaIn3 has the highest value of electrical conductivity per relaxation time and thermal conductivity per relaxation time are 9.43 x 1020 1/Ωms and 107.65 x 1014 W/mKs respectively. LaTl3 has the highest figure of merit among these materials.

The effect of acceptor and donor doping on the electronic properties of the half-Heusler TiNiSn.

Optimizing the electronic transport properties of thermoelectric compounds is commonly achieved by either donor or acceptor atom doping to increase the conduction of the appropriate carrier type, electrons or holes, respectively. Enhancing carrier mobility and carrier concentration will both lead to optimized electronic properties. In this work the effect of various dopants on the electronic properties of TiNiSn was explored, by modeling the doping of an ideal compound on the Ti-sublattice with acceptor or donor elements. Using ab initio DFT calculations and a set of analytical expressions of transport properties, the temperature dependencies of the electronic properties were calculated, to examine possible n-type or p-type dopants to be used in further experimental studies.

Recent Developments in Applications of G-CuO Nanocomposites for Photocatalytic Dye Removal

Abstract The extensive application of synthetic dyes across industries poses significant environmental challenges, particularly concerning water quality degradation. Regarding the possible solutions, copper oxide (CuO) stands out as a feasible candidate. Being a p-type Nano-heterogeneous semiconductor with a bandgap of 1.2–2.71 eV, CuO is a reasonable choice and widely studied photocatalyst for addressing such challenges. When the wavelength exceeded the UV-visible region, its functionality showed deterioration. At the same time, there are difficulties associated with reproducibility and reusability, as well as rapid electron-hole recombination, which prevent the widespread application of this technology within this spectral range. In an attempt to eliminate this defect, researchers have been investigating strategies to activate CuO under visible light, with one promising approach being carbon nanomaterials such as graphene to form carbon-CuO composites. The unique properties of graphene, i.e., its large surface area and excellent electron mobility, make it a remarkable candidate for the enhancement of CuO photoactivity. This study highlighted the recent progress in the synthesis of graphene-based CuO photocatalysts, with the main characteristic of extending the light absorption capacity of CuO into the visible spectrum. It reveals achievements in material innovations and applications, with a focus on photocatalytic dye degradation. These breakthroughs are a sign that the field is growing in popularity and is evolving.

Organic-inorganic hybrid dye-sensitized solar cells with bismuth ferrite sandwiched between rhodamine-6G and helical ZnO-dense nano-chains

Abstract Organic–inorganic hybrid dye-sensitized solar cells (DSSC) were grown on a conducting glass substrate employing multiple layers of bismuth-ferrite (BFO) sandwiched between Zinc oxide helical nanochain and Rhodamine- 6 G dye. The zinc oxide layer has been used as a n-type semiconductor window layer. To increase the carrier concentration ZnO has been doped with aluminium. The bismuth ferrite layer served as an electron-blocking layer, while rhodamine 6 g acted as a dye synthesizer. When the window layer is pure ZnO and the BFO layer is properly optimized, solar cell efficiency increases from 0.7% to 1.3%. Aluminum doping in ZnO, combined with an identical BFO layer, increases efficiency from 1.37% to a maximum of 2.1% without employing any kind of electrolyte. Doping the Zn site with Al enhances the efficiency of such a DSSC structure by 1.53 times. BFO limits charge recombination, which leads to enhanced efficiency as an outcome. A parametric analysis was carried out to determine the optimal BFO thickness for increased solar cell efficiency. The main advantages of this optimal DSSC structure are that it is economical, efficient, and does not require any liquid electrolyte. The stability was higher because there was no use of liquid electrolytes.

Facile Synthesis of Bandgap-Engineered N-Doped MgO/g-C3N4 Nanocomposites for Enhanced Sunlight-Driven Photocatalytic Degradation of Organic Dyes

This study tests the theory of using a p-n junction to inhibit the recombination of photo-generated electrons and holes in N-MgO/g-C3N4 for the photocatalytic degradation of methylene blue (MB) dye. While the use of n-type semiconductor junctions with g-C3N4 for bandgap narrowing is well-studied in dye degradation, this research explores the innovative application of nitrogen (N)-doped MgO to create a p-type junction with n-type g-C3N4. The N-MgO/g-C3N4 nanocomposites were designed and synthesized to leverage both the bandgap narrowing effect and the formation of a p-n junction. The results demonstrate that these nanocomposites can effectively degrade MB dye under sunlight, achieving over 90% degradation efficiency with a bandgap of 2.63 eV. Under high pH conditions, the degradation efficiency further increased to 94%. The enhanced photocatalytic activity of the N-MgO/g-C3N4 composite is attributed to the formation of a heterojunction, which facilitates efficient separation and transmission of photo-induced charge carriers. This study discusses the detailed mechanism of this enhanced activity, emphasizing the role of the p-n junction in promoting effective charge separation and transfer, thereby improving the photocatalytic performance under sunlight.

Exploring the role of carbon nitrides (melem, melon, g-C3N4) in enhancing photoelectrocatalytic properties of TiO2 nanotubes for water electrooxidation

Carbon nitrides (CNs), synthesised from melamine at temperatures 400 °C or 525 °C with their derivatives prepared by acidic protonation and oxidation using H2SO4 are tested as co-catalysts for oxygen evolution reaction (OER) modifying anodic Titania nanotubes (TiO2–NTs) surface. Materials exhibit crystalline structures and contain tri-s-heptazine rings with different terminal groups (–NH2, –NHOH, –NO2, –OH, =O), which are important for their catalytic and photoelectrocatalytic performance. These materials exhibit p-type semiconductor behaviour. Heterojunctions formed by n-type TiO2 and p-type carbon nitrides were tested using linear sweep voltammetry (LSV) in the dark and under illumination in the potential range allowing the water oxidation reaction to proceed. It is demonstrated, that the presence of –NH2 functional groups play a considerable role in OER kinetics in the dark. Changes in photocurrent at the anodic potential range are discussed considering Z–scheme heterojunction formation promoted with the catalytic activity of –NH2/– NHOH pending groups. Acid-treated melem in junction with Titania nanotubes emerges as the best co-catalyst for anodic water oxidation in the dark, with a Tafel slope of 83 mV/dec. This research encourages further exploration of melem and melon co-catalysts for improved electro- and photoelectrocatalytic applications.

Liquid-phase deposition of [formula omitted] heterojunction thin film photoanode for water splitting

The Liquid-phase deposition (LPD) method stands out as one of the most cost-effective techniques for fabricating thin films, due to its simple equipment requirements, low operational costs, and easy scalability while maintaining excellent film quality. In this work, we successfully demonstrate for the first time the synthesis of a heterojunction thin-film photoanode of hematite (α-Fe2O3) on an n-type silicon (n-Si) substrate using LPD. The α-Fe2O3/n-Si heterojunction photoanodes fabricated by LPD exhibited superior photocurrent responses for water splitting, with greater light absorption and enhanced performance compared to photoanodes prepared on fluorine-doped tin oxide (FTO) glass substrates, indicating the high quality of the heterojunction interface. The LPD-fabricated heterojunctions showed an early onset of photocurrent at lower applied potentials compared to Pt-based metal electrodes, demonstrating a reduction in overpotential voltage of 0.3 V. Overall, the LPD method shows promising potential for fabricating high-quality α-Fe2O3/n-Si thin films, with potential applications toward unassisted water splitting, offering an efficient and sustainable approach for green hydrogen production.

Comparative Study of Silicon and Silicon Carbide Semiconductors

This research paper provides an in - depth comparison of intrinsic and extrinsic semiconductors, focusing on their electrical properties, mechanisms of operation, and implications for technological applications. Through a detailed examination of band theory, charge carrier dynamics, and the impact of doping, this study elucidates the fundamental differences between these two types of semiconductors. Utilizing silicon as the primary material, the paper explores how these differences influence the efficiency and functionality of semiconductor devices, addressing potential uncertainties in experimental methodologies and highlighting recent breakthroughs in the field.

An emerging aspirant for solar cell and non-conventional energy applications: Lead free fluoro-perovskites A2TlInF6 (A = K, Rb)

In the present work; structural, electronic, optical, and thermoelectric properties of double perovskites A2TlInF6 (A = K, Rb) have been studied using the ab-initio method in conjunction with full potential Linear Augmented Plane Wave (FP-LAPW) method and PBE-GGA potential. Structural properties, cohesive energy, and formation enthalpy collectively confirmed the stability of the halide perovskites in a cubic structure with Fm3m symmetry. Electronic properties revealed the p-type semiconductor nature of both materials. The indirect band gap values for K2TlInF6 and Rb2TlInF6 were found to be 3.489 eV and 3.591 eV, respectively, with PBE. With PBE + SOC, the values dropped to 3.445 eV and 3.546 eV, respectively. Optical properties such as Dielectric function εω, Refractive Index nω, Extinction Coefficient κω, Optical Conductivity σ(ω), Reflectivity R(ω), Electron Energy Loss Function L(ω), and Absorption Coefficient αω were determined using PBE-GGA potential. BoltzTraP code was used to determine thermoelectric properties, namely, Seebeck Coefficient (S), Electrical Conductivity (σ), Thermal Conductivity (K), Power Factor (PF), and Figure of merit (ZT) which were studied in detail. The study suggests halide-based double perovskites may have the potential for solar energy utilization due to their high absorption coefficient, large values of refractive index, and optimal values of the figure of merit.

Enhancing electrochemical performance of Co3O4/ZnO composite nanostructures through interface engineering for oxygen evolution reaction

Co3O4/ZnO composite nanostructures were successfully synthesized via a simple hydrothermal method followed by air-based calcination at 500°C. The resulting hexagonal heterostructure composite with a large interfacial area demonstrates exceptional oxygen evolution electrocatalytic activity with an overpotential of 288 mV at 10 mA cm-², and a low Tafel slope (80 mV dec⁻¹). This enhanced activity is attributed to the Co3O4/ZnO p-n junction, where ZnO (an n-type semiconductor) and Co3O4 (a p-type semiconductor) meet, which is crucial for boosting catalytic activity. This interface enables swift electron movement between the two materials, resulting in better charge separation and decreased charge recombination. Additionally, the high active surface area, confirmed by cyclic voltammetry measurements, further contributes to the improved OER performance. The well-defined interfaces within the Co3O4/ZnO heterostructures provide abundant active sites, facilitating efficient charge transfer kinetics. This research highlights the potential of composite heterostructures as promising electrocatalysts for water-splitting applications.

Ligand-Tuned AgBiS2 Planar Heterojunctions Enable Efficient Ultrathin Solar Cells.

AgBiS2 quantum dots (ABS QDs) have emerged as highly promising candidates for photovoltaic applications due to their strong sunlight absorption, nontoxicity, and elemental availability. Nevertheless, the efficiencies of ABS solar cells currently fall far short of their thermodynamic limits due in large part to sluggish charge transport characteristics in nanocrystal-derived films. In this study, we overcome this limitation by tuning the surfaces of ABS semiconductor QDs via a solvent-induced ligand exchange (SILE) strategy and provide key insights into the role of surface composition on both n- and p-type charge transfer doping, as well as long-range charge transport. Using this approach, the electronic properties of ABS films were systematically modulated, thereby enabling the design of planar p-n heterojunctions featuring favorable band alignment for solar cell applications. Carrier transport and separation are significantly enhanced by the built-in electric fields generated within the ultrathin (30 nm) ABS heterojunction absorber layers, resulting in a notable solar-cell power conversion efficiency of 7.43%. Overall, this study presents a systematic and straightforward strategy to tune not only the surfaces of ABS, but also the electronic properties of solid-state films, thereby enabling junction engineering for the development of advanced semiconductor structures tailored for photovoltaic applications.

P-Type Cross-Linked Silicon Nanocomposites for Improving the Lithium-Ion Deinsertion from Anode Materials of Lithium-Ion Batteries

P-Type Cross-Linked Silicon Nanocomposites for Improving the Lithium-Ion Deinsertion from Anode Materials of Lithium-Ion Batteries

Molecular Design of n-Type Organic Semiconductors with Ultralow Electron Reorganization Energies.

Bottom-up design of n-type organic semiconductors with salient electron-transport properties is of fundamental importance. Here, with the aid of density functional theory, we demonstrate that condensing odd-membered carbon rings (5MR/7MR) to small polycyclic aromatic hydrocarbons (PAHs) can endow molecules with ultralow electron reorganization energies (λ < 100 meV). Studying 60 molecules, we find that introducing polycyclic fragments with built-in 5MR and 7MR to linear PAHs at the Cα,β positions or to nonlinear PAHs in D2h symmetry constitutes molecules with λ as low as 65 meV. A joint ACID and NICS analysis proves that the stronger the molecular aromaticity, the lower the λ will be. This is contrary to what has been previously found for p-type molecules. Furthermore, we propose "acupoints" on molecules for N-doping and cyanation, which can be used to precisely locate the substitution sites to reduce the LUMO energies (in favor of electron injection and air stability) of low-λ molecules while it does not elevate λ. These findings would help to reduce the synthetic blindness/cost and contribute to the bottom-up design of n-type small-molecule organic semiconductors.