Post-annealing Temperature Research Articles

Improving the minority carrier lifetime of PERC solar cells via bi-layer rear interface passivation strategy

Passivated emitter and rear contact (PERC) based solar cells are dominating the current photovoltaic (PV) market due to their high power conversion efficiency (PCE) and low cost. However, issues like the lower minority carrier lifetime (MCLT) and high density of surface dangling bonds are limiting their further improvement in PCE. To overcome this issue, a bi-layer rear interface passivation strategy is developed with the ultra-thin Al2O3 and SiO2 layers in PERC solar cells. Applying single (Al2O3) and double (SiO2/Al2O3) passivation layers revealed that each process parameter such as plasma conditions, deposition temperature, post-annealing temperature, and the film thickness in the ALD process affect the MCLT values as well as overall device performance. Especially, post-annealing treatment which improves crystallinity, and reduces interfacial defects was found to be most influential for the MCLT value. The single Al2O3 layer applied in PERC solar cells revealed an increase and decrease in MCLT values at a relatively lower (<10 nm) and higher thickness (>15 nm), respectively. Further, integration of SiO2 with the Al2O3 layer showed its more prominent effect than just single Al2O3 and SiO2 passivation layers. An optimal SiO2 thickness combination (4 nm) with an Al2O3 layer (12 nm), demonstrated reduced density of surface dangling bonds and diffusion of Al atoms from Al2O3 layers. As a result, it improved the carrier extraction yield by increasing the negative fixed charge. Finally, SiO2/Al2O3 (4/12 nm) double passivation layer post-annealed at 450 °C for 15 min delivers improved PCE from 19.4% to 19.9% in PERC solar cells.

A modified drop-casting technique for efficient lead-free, environment-friendly thin film CsBi3I10 perovskite solar cells

The efficiency of lead-based perovskite solar cell deteriorates due to their instability and toxicity which inhibits their commercial application. Both of these issues are resolved by substituting Bismuth in place of lead. In order to create environmentally friendly perovskite solar cells (PSCs), bismuth-based halide perovskite (CsBi3I10) is a promising absorber material. Bismuth-based CsBi3I10 perovskite films were fabricated using a modified drop-casting process at room temperature. With this technique, you can get a film with desirable characteristics including a smooth, uniform surface and no pinholes. A comprehensive analysis is carried out in this research article as a result of the fact that thermal annealing is the first step in the process of transforming the deposited solution into the perovskite material. Band gap tuning is achieved with the use of this heat treatment. As film that has been post-annealed at the low temperature of 60 °C is not only tuned in terms of conductivity with a low band gap of 1.78 eV, but it also has improved absorption. In contrast, hexagonal particles with a low absorbance and a greater band gap of 2.08 eV develop at higher post-annealing temperatures. Band gap is greater (2.21 eV) and nonhomogeneous layered structure is formed in the film that does not undergo any post annealing treatment. The effects of post-annealing temperature on morphological, structural, and optical properties are explored and connected with photovoltaic application requirements. Finally, the photovoltaic performance of PSCs based on CsBi3I10 without hole transport layer (HTL) is investigated quantitatively in this study.

Novel gamma-ray enhanced TiO2 nanoparticles photoanode for efficient photoelectrochemical (PEC) water splitting

The photocatalytic activity of TiO2 nanoparticles (TiO2NPs) for Hydrogen Evolution Reduction (HER) was significantly enhanced through a multi-step process involving oxygen-doping with γ-ray irradiation treatment (ranging from 10 kGy to 100 kGy), methanolic dispersion, and post-annealing temperatures. Remarkably, γ rays induced oxygen-doping, leading to improved electronic properties and chemical bonding, as demonstrated in the XPS section, which ultimately contributed to the exceptional stability of the photoanode. The resulting higher crystallinity and larger crystallite sizes, evident in Raman and XRD spectra, further enhanced the structure of the TiO2NPs. Upon γ irradiation, the deposited TiO2NPs exhibited enlargement and agglomeration, which promoted enhanced surface area, catalytic sites, and light absorption when used as a photoanode in PEC cells. The post-irradiation conditions caused a reduction in the energy band gap, resulting in a quenching effect from 3.25 eV to 3.18 eV. Intriguingly, PL analysis showed that the radiated photoanode displayed a remarkable reduction in the energetic separation of photo-generated electron-hole pairs, accompanied by a simultaneous decrease in carrier recombination. Overall, the 70 kGy TiO2NP photoanode demonstrated exceptional photostability and significantly outperformed the pure TiO2NP counterpart by increasing the photocurrent density by over 300%, reaching approximately 100.12 μA cm−2 at 1.23 vs. RHE, compared to 36.42 μA cm−2 for the pure TiO2NP. These findings underscore the significance of gamma irradiation in the field of nanomaterials and its promising potential for photoelectrochemical (PEC) solar water splitting applications.

Enhanced the thermoelectric power factor of n-type Bi2Te3 thin film via energy filtering effect

In recent years, Bi2Te3 thin films have gained interest in the field of thermoelectric power generation due to their promising thermoelectric performance. However, the poor performance of Bi2Te3 has limited its widespread applicability. To address this, we deposited Bi2Te3 films on soda lime glass substrates via thermal evaporation and annealed them at different temperature ranges between 100 and 350 °C. Our X-ray diffraction analysis showed that the best quality film was produced at a post-annealing temperature of 350 °C, while the as-deposited sample yielded a low-quality film. We then analyzed the surface morphology of the prepared sample using scanning electron microscopy and found that the grains were highly intact with a uniformly aligned granular surface morphology and no porosity. By controlling the density and grain size, we were able to improve the Seebeck coefficient and electrical conductivity. Specifically, the Seebeck coefficient value increased up to 135 μV/°C due to the energy filtering effect at small grain boundaries, while the electrical conductivity improved by raising the charge carrier mobility and reducing grain size, thus increasing the conductivity of the tiny domain. Consequently, the Bi2Te3 thin film with a small grain size exhibited the highest thermoelectric power factor of 15.30 μW cm−1 C−2 at room temperature. Our findings suggest that the thermal evaporation technique is an effective method for growing Bi2Te3 thin films with improved thermoelectric properties.

Enhancing thermoelectric properties of CuNiO thin films through post-annealing: Effect on Seebeck coefficient and power generation

The need for the best thermoelectric power generation to extract low-grade heat energy from the human body has generated considerable interest. However, developing oxide-based thermoelectric materials with both high stability and Seebeck coefficient remains challenging. In this work, we have prepared CuNiO thin film with an economical and simple thermal evaporation method and post-annealed at different temperatures from 400 to 550 °C. XRD and SEM have determined the crystal structure and surface morphology of the CuNiO thin film. The electrical conductivity and charge carrier concentration increase with post-annealing temperature due to the formation of the secondary phases. The Seebeck coefficient has decreased from 65.1 to 37.9 µV/K with post-annealing temperature due to improved charge carrier density, the electronic band structure of the material and secondary phases. The maximum power factor has been achieved in the unannealed sample.

B2O3 as an effective additive for cold sintering of MgTiO3

In the present study, B2O3 has been introduced as an effective additive for the cold sintering of MgTiO3 as a microwave dielectric ceramic. Furthermore, the effects of various cold sintering parameters, including cold sintering temperature, post-annealing temperature, sintering process time, and B2O3 quantity have been investigated. The results proved that high-quality samples with a relative density of more than 96% can be obtained by using 15 wt% B2O3 and cold sintering at 200 °C under an applied pressure of 250 MPa for 1 h and post annealing at 1100 °C. X-ray diffraction (XRD) analysis confirmed the absence of any reaction between the two phases. Moreover, the MgTiO3- 15 wt% B2O3 ceramics show excellent microwave dielectric properties, including a low relative permittivity (εr) of 14.5, a high-quality factor (Q×f) of 39,000 GHz, and a temperature coefficient of frequency (TCF) value of −54.36 ppm/°C.

Performance optimization of nanometer-thin indium-tin oxide transistors by two-step air annealing

In this study, the influence of air annealing on nanometer-thin indium tin oxide (ITO) transistors was investigated. Compared with unannealed devices, the field-effect mobility and subthreshold swing of ultrathin ITO transistors with pre-annealing, post-annealing, and two-step annealing were greatly improved. Under a pre-annealing temperature at 200 °C and post-annealing temperature at 100 °C, the ultra-thin ITO transistors showed field-effect mobility of 34.2 cm2/Vs, steep subthreshold swing of 1.95 V/decade, and high Ion/Ioff ratio of 2.46 × 107. X-ray photoelectron spectroscopy revealed that the performance changes could be ascribed to the changes in the oxygen vacancies in the ITO channel under different annealing conditions. The dependence of subthreshold swing on the annealing process may be related to the absorption and release of water molecules from the ultrathin ITO surface. Overall, these results emphasize the importance of the annealing procedures for nanometer-thin ITO transistors.

Preparation of In0.5Sc1.5Mo3O12 nanofibers and its negative thermal expansion property

Orthorhombic In0.5Sc1.5Mo3O12 nanofibers were prepared by electrospinning followed by a heat treatment. The effects of post-annealing temperatures on the phase composition, microstructure and morphology were investigated by XRD, SEM, HRTEM and XPS. Negative thermal expansion (NTE) behaviors of the In0.5Sc1.5Mo3O12 nanofibers were analyzed by high-temperature XRD. Results indicate that the as-prepared In0.5Sc1.5Mo3O12 nanofibers show an amorphous structure with smooth and homogeneous shape. The average diameter of the as-prepared In0.5Sc1.5Mo3O12 nanofibers is around 515 nm. Well crystallized orthorhombic In0.5Sc1.5Mo3O12 nanofibers could be prepared after post-annealing at 550 °C for 2 h with an average diameter of about 192 nm. The crystallinity of In0.5Sc1.5Mo3O12 nanofibers gradually improved with the increase of annealing temperature. However, too high post-annealing temperature leads to a damage of sample's fiber structure. The high-temperature XRD results reveal that In0.5Sc1.5Mo3O12 nanofibers show an anisotropic NTE, and the coefficients of thermal expansion (CTEs) along a-axis and c-axis were −5.95 × 10−6 °C−1 and -3.54 × 10−6 °C−1, while the one along b-axis is 5.61 × 10−6 °C−1. The volumetric CTE of In0.5Sc1.5Mo3O12 nanofibers is −3.90 × 10−6 °C−1 and the linear one is 1.3 × 10−6 °C−1 in 25–700 °C.

Enhanced thermoelectric performance of P-type SnTe thin film through Sr doping and Post-Annealing treatment

Lead-free tin telluride (SnTe) has gained significant attention for its potential use in mid-temperature thermoelectric power generation. In this work, we systematically analyzed the thermoelectric power factor of Sn0.7Sr0.3Te thin films at various post-annealing temperatures through structural, morphological, and thermoelectric property measurements. Our findings show that Sr-doping in the SnTe thin film matrix and post-annealing treatment can significantly enhance the thermoelectric properties by modifying the band structure and introducing an energy-filtering effect at grain boundaries. We achieved a maximum power factor of 29.4 μWm-1K−2 at 523 K for Sn0.7Sr0.3Te thin films post-annealed at 1073 K, which is three times greater than that of pure SnTe. This work demonstrates that Sr-doping and post-annealing effects can tune the band gap, induce band degeneration, and reduce grain size, resulting in a high thermoelectric power factor of the SnTe thin film.

Effects of growth cycle number and annealing temperature on Ga2O3-on-quartz solar-blind photodetectors

In this study, Ga2O3 thin films were deposited on quartz glass substrates by atomic layer deposition technique followed by post annealing process. The influence of growth cycle number and post annealing temperature on both their material characteristics and UV photoelectric properties was studied. The crystal structure can be improved and the photo-current increases in a geometric progression with the increase of the number of cycles. In addition, the effect of annealing temperature on Ga2O3-based solar-blind photodetectors have been studied. The annealing temperature was set to 400 °C, 500 °C, 600 °C, 700 °C, 800 °C and 900 °C, respectively. The surface morphology deteriorates seriously when the annealing temperature is above 600 °C, leading to the poor photoresponsivity (<1 A/W) of Ga2O3 PDs. The amorphous Ga2O3 film annealed at 400 °C in N2/Air mixture atmosphere shows the maximum disorder and minimum optical band gap, which results in the lower UV transmittance and higher photoresponsivity of 1166.6 A/W under 254 nm illumination. The results show that the Ga2O3 photoelectric detectors based on quartz substrate not only reduces the cost of solar-blind photodetectors cost, but also has excellent photoelectric performance.

Effect of temperature on structural phase transition and photoluminescence in organic-inorganic hybrid CH3NH3PbI3-xClx perovskite

Organic-inorganic hybrid (CH3NH3PbI3-xClx) perovskite is a useful light accumulating material. Its characteristic features are found to be very sensitive to synthesis and environmental conditions. We studied its structural phase transformation, inter band transitions, and photoluminescence as a function of temperature, which are key parameters governing its light absorbing characteristics. We found that photoluminescence peaks exhibit several finer features, which are identified, deconvoluted, and discussed in detail. Our analyses revealed the presence of multiple phases, defects (mainly Cl), excitonic binding energies, and radiative recombination of trap states in the perovskite. Based on the results, a schematic energy band diagram has been proposed, and it is concluded that the trap states will become less active at elevated temperatures. Moreover, increased post annealing temperature will decrease the recombination at interfaces due to improved crystallinity and large grain sizes. Control over the surface and interface trapping by using the appropriate working and annealing temperature for the device may be key to increasing the efficiency of perovskite based solar cells.

Effect of the Working Pressure and Oxygen Gas Flow Rate on the Fabrication of Single-Phase Ag2O Thin Films

Ag2O thin films have been applied in various devices, such as photodetectors, photocatalysts, and gas sensors, because of their excellent thermal stability, strong electrical properties, and stable structures. However, because various phases of silver oxide exist, the fabrication of single-phase Ag2O thin films using a general deposition system is difficult. In this study, Ag2O thin films were deposited on glass substrates at different working pressures and O2 gas flow rates using a facing-target sputtering (FTS) system. After optimizing the working pressure and O2 gas flow rate, the Ag2O thin films were post-annealed at different temperatures ranging from 100 to 400 °C to improve their crystallographic properties. The X-ray diffraction patterns of the as-fabricated Ag2O thin films indicated the presence of a single phase of Ag2O, and the ultraviolet–visible (UV–vis) spectral analysis indicated transmittance of 65% in the visible light region. The optimum working pressure and O2 gas flow rate were determined to be 4 mTorr and 3.4 sccm, respectively. Finally, the effect of the post-annealing temperature on the thin film was investigated; the Ag2O peak had high intensity at 300 °C, suggesting this as the optimum post-annealing temperature.

Perpendicular Magnetic Anisotropy of an Ultrathin Fe Layer Grown on NiO(001)

The magnetic anisotropy and magnetic interactions at the interface between $\mathrm{Fe}$ and $\mathrm{Ni}\mathrm{O}$(001) were investigated. Depending on the growth conditions of the $\mathrm{Ni}\mathrm{O}$(001) layers and the postannealing temperature, the preferential magnetization direction of the ultrathin $\mathrm{Fe}$ layer grown on a $\mathrm{Ni}\mathrm{O}$(001) layer changed from the in-plane direction to a direction perpendicular to the film plane. The lattice constant of the $\mathrm{Ni}\mathrm{O}$(001) layers parallel to the growth direction increased with ${\mathrm{O}}_{2}$ flow rate, while that parallel to the in-plane direction were locked onto the MgO(001) substrate regardless of the growth conditions of the NiO layers. Moreover, perpendicular magnetization was observed only when the NiO layer was grown with ${\mathrm{O}}_{2}$ flow rates higher than 2.0 sccm corresponding to oxygen-rich NiO. X-ray magnetic circular dichroism measurements revealed an enhancement in anisotropic orbital magnetic moments similar to the origin of perpendicular magnetic anisotropy at the $\mathrm{Fe}$/MgO(001) interface. The interfacial magnetic anisotropy energies were 0.93 and $1.02\phantom{\rule{0.2em}{0ex}}{\mathrm{mJ}/\mathrm{m}}^{2}$ at room temperature and at 100 K, respectively, indicating less temperature dependence. In contrast, the coercivity ${H}_{c}$ exhibited a significant temperature dependence. Although no signature of exchange bias or unidirectional loop shift was observed, ${H}_{c}$ was strongly dependent on the NiO layer thickness, indicating that the exchange interaction at the interface between the ferromagnetic and antiferromagnetic layers was not negligible, despite the NiO(001) being a spin-compensated surface.

Optimizing a microwave-combustion synthesis and particle-size dependent magnetic properties of M-type Sr ferrite

A chemical-route synthesis of SrFe12O19 nanoparticles was achieved by a facile microwave combustion followed by post annealing at a temperature lower than that required for a conventional synthesis. The synthesis of nano and fine particles of a single M-type ferrite phase was optimized by systematic investigations for effects of the starting Fe/Sr ratio and the post annealing temperature. Single- and multi-domain magnetic behaviors were distinctly observed for particles annealed at temperatures below and above 1000 °C, respectively. Room-temperature intrinsic coercivity up to Hc ∼6.3 kOe, saturation magnetization up to Ms ∼70 emu/g, and magnetic squareness ratio up to Mr/Ms ∼0.51 were obtained for the M-type Sr-ferrite particles.

Rapid Thermal Annealing Process Toward Enhancement of ITO Thin Films

Indium tin oxide (ITO) thin films with 100 nm thickness were successfully deposited on soda-lime glass substrates by metal oxide electron beam evaporation at room temperature. The deposited films were post annealed via rapid thermal processor (RTP) in vacuum environment at 400 to 550 °C. All deposited ITO thin films were studied on the structural, electrical, and optical properties. Results showed that the post annealing treatment by RTP improved the crystallinity, increased crystallite size, and increased surface roughness values. Higher RTP post annealing temperature also enhanced the electrical performance that led to higher transmittance of ITO thin films.

Postannealing Temperature Effects on the Etching Behavior and Field Emission Properties of Cu‐Implanted Diamond

To investigate the postannealing temperature effects on the surface etching behavior and electron field emission (EFE) properties of the Cu‐implanted microcrystalline diamond (MCD) films, they are subjected to furnace annealing in a temperature range of 600–900 °C under N2 atmosphere at a rapid annealing rate. The etching behavior happens when the samples are annealed at 700 °C and above. The EFE performances enhance first and then decrease with the increasing annealing temperature. The optimum EFE property with a low turn‐on field of 6.42 V μm−1 is obtained after the Cu‐implanted MCD film is annealed at 700 °C. The enhancement in EFE properties originates from the presence of nanographitic phase and the formation of electron‐rich Cu nanoparticles, which encourage a higher efficient electron transport. In contrast, the structural studies reveal that when the samples annealed at 800 °C and above, Cu nanoparticles evaporate from the diamond surface and the sp2‐bonded carbon decomposes. Consequently, etch pits appear on the surface of the MCD sample. Moreover, it demonstrates that graphitization is the dominant mechanism of the diamond surface etching behavior and the enhancing of EFE properties.

P-channel NiO thin film transistors grown with high k ZrO2 gate oxide for low voltage operation

A low voltage operative and optically transparent p- type Nickel oxide thin film transistor (TFT) was realized. We have systematically investigated the structural and transport properties of both NiO and ZrO2 thin films grown by dc magnetron sputtering. It is shown that a 30 nm thickness of ZrO2 thin film act as gate oxide dielectric for the TFTs. The Metal-Insulator-Metal (MIM) study revealed a high dielectric constant (k) of 28 and the leakage current density significantly persisted at ∼1 nA cm−2 at an applied field of 7 MV cm−1. Further, active layer of p-NiO film was deposited on ZrO2 gate oxide dielectric film and were processed at different post annealing temperatures. The TFTs electrical characteristics with the staggered bottom gate configuration of ITO/ZrO2/NiO/Ag exhibits a stable 104 of Ion/Ioff ratio with a field effect mobility of 15.8 cm2V−1s−1 and recorded sub-threshold swing slope of 512 mV/dec. Moreover, the trap density of 1.82 × 1012 cm−3 was estimated from the Levinson’s plot. Overall, the post annealing temperature seems to improve the transport characteristics of the fabricated TFTs.

Control of inhomogeneity and magnetic properties of ZnO:Co films grown by magnetron sputtering using nitrogen

We experimentally report the control of structural inhomogeneity and magnetic properties of Co-doped ZnO films using nitrogen mediated-crystallization. The ZnO:CoN were grown on a silicon substrate at room temperature by RF-magnetron sputtering using nitrogen and followed by a post-annealing treatment for 3 hours at 400 °C, 600 °C, 800 °C and 1000 °C in the air. This method induces changes in inhomogeneity properties comprised by microstructure and stoichiometry of each film, which are confirmed by X-ray diffraction, thermal desorption, and X-ray fluorescence measurements. The difference in inhomogeneity has led to the transformation in the magnetic properties. Films annealed at 400 °C, which showed the highest inhomogeneity, exhibited superparamagnetic-ferromagnetic properties. In contrast, all the other films exhibited diamagnetic properties. Increasing the post-annealing temperature above 400 °C reduces inhomogeneities indicated by improved grain size, decreased impurities, and lattice parameters and stoichiometry of ZnO:CoN films approached those of pure ZnO. Our present results will contribute to control the inhomogeneity of ZnO:Co films to improve magnetic properties at room temperature.

The optical properties of In2S3 films in the far-infrared spectral range

Optical reflection spectra of In2S3 thin films (180 – 730 nm) deposited on glass substrates are measured by infrared spectroscopy using the synchrotron radiation of BESSY II storage ring in the spectral range of 30 – 8000 cm−1. The aim of the study is to find the influence of different substrate and post-annealing temperatures on the electron and phonon systems of In2S3 films deposited on glass. Clear features in the reflectance spectra for the studied films have been found mainly in the phonon excitation range 100 – 400 cm−1. The experimental dielectric functions ε(ω) of In2S3 films are found to be in good agreement with the calculated ones obtained for In2S3 crystals within the density functional theory. The dielectric functions ε(ω) of the films in the range of 100 – 400 cm−1 depend substantially on the post-annealing temperature. This indicates a transition of the film from the amorphous to the crystalline state. The thorough analysis of the frequency dependence of the reflection coefficient R(ω) and optical conductivity σ(ω) in the wavenumber range of 30 – 130 cm−1 allowed us to reveal the distributed electron states in In2S3 films.

The role of hydrophobic molecules in the optoelectronical attributes of triple-cation perovskite solar cells

The partial modification of perovskite cations has already been done to stabilize perovskite solar cells (PSCs). In this study, Cs/FA/MA triple-cation (3D) perovskite and PTA2PbI4 (2D)/3D perovskite were used as light-absorbing materials in PSCs. Phenyl trimethylammonium iodide (PTAI) was also used as a passivator. It was found that PTAI can serve as an original PTA two-dimensional (2D) cation and as a basis for the formation of 2D/3D heterostructure films. Since an improper post-annealing temperature leads to the uncontrollable degradation of 3D perovskites, this study examines post-annealing at various temperatures to make a 2D perovskite film on a 3D perovskite layer. The proper post-annealing temperature to make a 2D/3D structure was 150 °C exerted for five minutes. Through PTAI post-treatment in these optimum conditions, the morphology of the perovskite layer was improved, which confirms the facilitation of the charge transfer. Indeed, a 2D/3D heterostructure originating from a PTAI solution serves as a film to protect perovskite layer from destruction and improves charge transfer. Therefore, the treatment of perovskite layers, as practiced in this study, can enhances the stability and the efficiency of hole-transport-free PSCs and predispose their industrial production. The efficiency of the optimized device was enhanced for 35 % in comparison to the control samples. The device could also maintain 90 % of its PCE for 177 days.