Annealing Window Research Articles

Low temperature method-based evaporation/spray-coating technology for wide bandgap perovskite solar cells

Years of working on perovskite solar cells (PSCs)-based tandem devices and single-junction devices have approved that low annealing temperatures can be beneficial for improving device performances. In this study, pseudo-halogen ion engineering works well in the evaporation/spray-coating method. According to our research, it is has been proven that the addition of formamidine acetate (FAAc) can effectively reduce the annealing temperature from 170 °C to 150 °C, accelerate the maturation process of the perovskite films, and broaden the annealing window. As a result, a perovskite film with homogeneous crystallization and low residual stress is achieved, leading to extended charge carrier lifetimes, elevated photoluminescence quantum yields (PLQY), reduced Urbach energies. The corresponding PSCs were prepared through evaporation/spray-coating method achieves an impressive power conversion efficiency (PCE) of 19.46%, which is the highest efficiency among wide-bandgap (WBG) PSCs fabricated by this method. And the unencapsulated devices exhibit satisfactory stability, retaining 80% of the initial PCE after 600 h of thermal aging at 60 °C and retaining 90% of the initial PCE after 1500 h of 50% humidity aging at 25 °C, respectively.

Aging‐Resistant Precursor with Ultrawide Annealing Window for 24.08% Perovskite Solar Cells

AbstractPerovskite solar cells (PSCs) have attracted extensive attention in the photovoltaic field, with their highest power conversion efficiency (PCE) reaching 26%. However, the commercialization of PSCs is severely hindered by the instability of precursor solutions and the narrow annealing window for perovskite films. Here, 2,3,5‐trichlorobenzaldehyde (3Cl‐BZH) is introduced into the organic salt precursor solution to eliminate excess organic amines through Schiff‐base reactions, avoiding subsequent irreversible amine‐cation reaction of formamidine‐methylammonium (FA‐MA+) and improve the stability of the precursor solution. Meanwhile, the chemical interaction between C═O group of 3Cl‐BZH and formamidinium (FA+) in the perovskite precursor contributes to the slow release of organic ions, which reduces the reaction rate between organic salt and PbI2, retarding the crystallization of perovskite film. The PSCs with a conventional annealing process achieve a champion efficiency of 24.08%, which derives from the defect passivation effect of 3Cl‐BZH. The PSCs with an ultrawide annealing window of 240 h for wet perovskite film in the air still maintain an efficiency of 22.01%. The aging‐resistant precursor and ultrawide annealing window are beneficial for reproducible, efficient, and low‐cost PSCs, which brings great prospects for the commercialization of PSCs.

Excellent soft magnetic properties and enhanced glass forming ability of Fe-Si-B-C-Cu nanocrystalline alloys

In the present investigation, the glass forming ability (GFA), thermal stability, and soft magnetic properties of Fe85Si6-xB8Cu1Cx alloys are investigated by the substitution of C for Si. It was found that the GFA of C-containing alloys is remarkably enhanced when a certain amount of Si is replaced by C in a C-free alloy. The temperature interval between the first and second crystallization temperatures is also improved by C addition and reaches a maximum value of 169 °C for the as-spun Fe85Si2B8Cu1C4 amorphous alloy. The Fe85Si4B8Cu1C2 nanocrystalline alloy exhibits the best soft magnetic properties with the highest saturation magnetic flux density (Bs) of 1.95 T and the lowest coercivity (Hc) of 4.1 A/m, which corresponds to the highest grain number density (Nd). The high GFA, large annealing window, low cost, and excellent soft magnetic properties enable the Fe85Si2B8Cu1C4 nanocrystalline alloy as a material with wide applicability. Moreover, this work is highly beneficial in balancing the relationship between a high Bs and sufficient GFA in the production of Fe-rich nanocrystalline alloys.

Effect of transverse magnetic field annealing on the magnetic properties and microstructure of FeSiBNbCuP nanocrystalline alloys

Improving the high-frequency magnetic properties of Fe-based nanocrystalline alloys with high-saturation magnetic induction (Bs) has received extensive attention recently. The magnetic properties, microstructure, and magnetic domain structure of Fe76Si12B8Nb2.2Cu0.8P1 ribbons after normal isothermal annealing (NA) and transverse magnetic field annealing (TFA) were investigated. It was found that NA and in situ crystallization TFA (TFA1) have little effects on the Bs and coercivity (Hc) of the ribbons but they significantly affect the magnetic permeability (μ) and optimal annealing window. In contrast, TFA after nanocrystallization (TFA2) enables the ribbons to attain a higher μ in a wide frequency range and a wider annealing temperature range than NA and TFA1. The TFA2 ribbons exhibit a high Bs of 1.45 T, low Hc of 0.8 A/m, and high μ under 1 A/m of 24,000 and 16,600 at 1 and 100 kHz, respectively. The factors causing the improved soft magnetic properties were revealed in terms of magnetic anisotropy and magnetization processes.

Effect of Ge Addition on Magnetic Properties and Crystallization Mechanism of FeSiBPNbCu Nanocrystalline Alloy with High Fe Content

In this work, new Ge-containing Fe-based nanocrystalline alloys with the composition of Fe80.2Si3B12-xP2Nb2Cu0.8Gex (x = 0, 1, 2 at.%) were developed, and the effects of Ge content on the magnetic and crystallization processes of the alloys were investigated. The addition of Ge extends the annealing window of the present Fe-based alloys, which reaches 173.6 K for the alloy of x = 2. The nanocrystalline alloy of x = 2, composed of dense and uniformly distributed α-Fe grains with an average grain size of 15.7 nm precipitated in the amorphous matrix, was obtained by conventional annealing treatment at a temperature of 843 K for 10 min, and this nanocrystalline alloy exhibited excellent magnetic properties with the Hc of 3 A/m and Bs of 1.65 T, which has great potential for industrial application. Non-isothermal crystallization kinetics studies show that the nucleation activation energy of the alloys gradually decreases with the increase in Ge content. The primary crystallization process is dominated by the direct growth of pre-existing nuclei in the as-spun alloy ribbons, and these pre-existing nuclei provide numerous heterogeneous nucleation sites to form dense and uniform α-Fe nanocrystals with a fine grain size, which leads to the excellent magnetic properties of the present Ge-containing Fe-based nanocrystalline alloys.

Nanocrystallization and Core-loss properties of Fe-rich FeSiBPNbCu nanocrystalline alloy

The present work investigates the structure, soft-magnetic and core-loss properties of 25 mm wide Fe83Si2B9P4Nb1Cu1 nanocrystalline ribbons. The melt-spun precursor ribbons of the thickness of 22 and 28 µm were prepared using commercial raw materials under ambient atmosphere. The XRD and DSC results show predominantly amorphous and hetero-amorphous structure for 22 and 28 µm ribbons in the as-quenched state. Further, the partial crystallization annealing leads to thickness dependent nanocrystallization process, wherein the thinner 22 µm ribbon shows sluggish primary(α-Fe(Si)) and delayed secondary(Fe3(B0.8P0.2)) crystallization process compared to 28 µm ribbons. The difference is explained through as-quenched precursor matrix structure and selective solute re-distribution of the intergranular region during nanocrystallization. Moreover, the higher crystallite size (D) and volume fraction(Vcr) of α-Fe(Si) nanocrystallites are observed for the 28 µm ribbon in the optimal annealing window. Under optimal annealing conditions, the 28 µm nanocrystalline ribbon (733 K) shows better AC soft-magnetic properties including B800 of 1.62 T, Hc of 15.7 A/m, Br/Bs ratio ≥ 0.8 compared to B800 of 1.59 T, Hc of 17 A/m and Br/Bs ratio ≥ 0.7 of 22 µm (743 K) ribbon. The 28 µm ribbon shows a low core loss (P) of 0.34 W/kg under 50 Hz, 1.5 T compared to P > 0.65 W/kg for 22 µm ribbons. The lower core-loss behaviour of thicker 28 µm in the sub-kHz frequency regime has been explained based on the nanocrystalline microstructure and loss coefficients (hysteresis and eddy current). The work compares the AC core-loss properties with reported Fe-rich nanocrystalline alloys and also discusses the scope of improving B800 beyond 1.65 T for the present alloys.

Fe-based amorphous alloys with superior soft-magnetic properties prepared via smelting reduction of high-phosphorus oolitic iron ore

Fe-based amorphous alloys generally suffer from the impurities in industrial raw materials and the high cost of pure raw materials. In this work, a revolutionary way for preparing Fe-based amorphous alloys from the refractory high-phosphorus oolitic iron ore with the combination of smelting reduction and melt-spinning was proposed for the simultaneously utilization of Fe and P elements. By using the smelting reduction, Fe–P alloys with high Fe and P recovery rate of 99% and 92% can be obtained, and the C content in the resultant Fe–P alloys can be accurately tailored by adjusting the C/O ratio. For the implementation of the developed process, the reduced Fe–P alloys with significantly different C content and the corresponding Fe83P3C1Si2B11, Fe76P5C3.8Si5.7B9.5 and Fe80P10C9Si1 (at. %) amorphous alloys with close C content were chosen. These resultant alloys all exhibit high AFA, low Hc and high μe as well as wide annealing window comparable to that of the alloys prepared with pure raw materials, demonstrating the feasibility of the developed process for energy-saving and resource-friendly production of soft-magnetic materials via smelting reduction of iron ores.

Unraveling the Impact of Halide Mixing on Crystallization and Phase Evolution in CsPbX3 Perovskite Solar Cells

Summary All-inorganic perovskite solar cells (PSCs) have attracted wide attention for their excellent thermal stability. However, the detailed crystallization process and complicated phase-transition mechanism of the CsPbX3 film with different halide compositions (I, Br, Cl) remain mysterious. In this study, systematic investigations are performed via state-of-art in situ grazing-incidence wide-angle X-ray scattering to understand the role of the halide elements in all-inorganic perovskite crystallization kinetics, phase-transition, and stabilization mechanism as well as how film morphology and grain size are affected. Based on these results, we were able to fabricate high-performance ternary halide (I, Br, Cl) all-inorganic PSCs through a precise compositional engineering. Our results provide guidance for an in-depth understanding of all-inorganic perovskite materials and pave the way to obtain high-performance all-inorganic PSCs.

Superior Textured Film and Process Tolerance Enabled by Intermediate-State Engineering for High-Efficiency Perovskite Solar Cells.

As the power conversion efficiency (PCE) of perovskite solar cells (PSCs) is increased to as high over 25%, it becomes pre‐eminent to study a scalable process with wide processing window to fabricate large‐area uniform perovskite films with good light‐trapping performance. A stable and uniform intermediate‐state complex film is obtained by using tetramethylene sulfoxide (TMSO), which extends the annealing window to as long as 20 min, promotes the formation of a high‐quality perovskite film with larger grains (over 400 nm) and spontaneously forms the surface texture to result in an improved fill factor and open‐circuit voltage (V oc). Moreover, the superior surface texture significantly increases the long‐wavelength response, leading to an improved short‐circuit current density (J sc). As a result, the maximum PCE of 21.14% is achieved based on a simple planar cell structure without any interface passivation. Moreover, a large area module with active area of 6.75 cm2 is assembled using the optimized TMSO process, showing efficiency as high as 16.57%. The study paves the way to the rational design of highly efficient PSCs for potential scaled‐up production.

Manipulating the Mixed-Perovskite Crystallization Pathway Unveiled by In Situ GIWAXS.

Mixed perovskites have achieved substantial successes in boosting solar cell efficiency, but the complicated perovskite crystal formation pathway remains mysterious. Here, the detailed crystallization process of mixed perovskites (FA0.83 MA0.17 Pb(I0.83 Br0.17 )3 ) during spin-coating is revealed by in situ grazing-incidence wide-angle X-ray scattering measurements, and three phase-formation stages are identified: I) precursor solution; II) hexagonal δ-phase (2H); and III) complex phases including hexagonal polytypes (4H, 6H), MAI-PbI2 -DMSO intermediate phases, and perovskite α-phase. The correlated device performance and ex situ characterizations suggest the existence of an "annealing window" covering the duration of stage II. The spin-coated film should be annealed within the annealing window to avoid the formation of hexagonal polytypes during the perovskite crystallization process, thus achieving a good device performance. Remarkably, the crystallization pathway can be manipulated by incorporating Cs+ ions in mixed perovskites. Combined with density functional theory calculations, the perovskite system with sufficient Cs+ will bypass the formation of secondary phases in stage III by promoting the formation of α-phase both kinetically and thermodynamically, thereby significantly extending the annealing window. This study provides underlying reasons of the time sensitivity of fabricating mixed-perovskite devices and insightful guidelines for manipulating the perovskite crystallization pathways toward higher performance.

Phase‐Specific Precipitation of Intermetallic Phases in Fe Al Mn Ni C Duplex Steels

A Fe–Al–Mn–Ni–C steel is designed explicitly to precipitate intermetallic phases in specific phases of a duplex steel. CALPHAD‐assisted alloy design is carried out with respect to an innovative “solublility‐assisted precipitation” (SAP) mechanism. A four phase equilibrium comprising of ferrite, austenite, κ‐phase (Fe3AlC), and B2‐phase (NiAl) is stabilized in a suitable annealing window. The processing conditions are adjusted according to elemental partitioning and consequential stabilization of κ‐phase in austenite and B2‐phase in ferrite. The feasibility of the SAP mechanism is validated by investigation of microstructure and precipitation evolution using electron microscopy and site‐specific atom probe tomography.

Investigation on the Formation Mechanism of In–N Codoped p-Type ZnCdO Thin Films: Experiment and Theory

Indium and nitrogen codoped ZnCdO films [ZCO:(In, N)] have been grown on quartz substrates by radio frequency magnetron sputtering deposition followed by ion-implantation technique. The room-temperature Hall measurements confirm that a stable p-type ZCO:(In, N) film is obtained by optimizing postimplantation annealing temperature (Tann) and time (tann). The Raman measurements reveal that the concentration of NO acceptors in stable p-type film is higher than unstable p-type films and much higher than n-type films, which indicates that choosing appropriate annealing window plays a key role in stabilizing the NO acceptors to obtain the stable p-type ZCO:(In, N). Both theory and experiment indicate that the stable p-type conductivity of ZCO:(In, N) is attributed to the formation of passive complexes (-Cd-O-In-N-), which can form an impurity band above the valence band maximum, resulting in a decrease in the ionization energy of the acceptor and an improvement in the stability of p-type ZCO:(In, N). The Hall measurements also confirm that the p-type films would convert to n-type conductivity under both higher Tann and longer tann. Combined with the transition state calculations, the possible reasons of such phenomenon are discussed in detail at the end of the article.

Study on the thermal stability of InN by in-situ laser reflectance system

The thermal stability of InN in the growth environment in metalorganic chemical vapor deposition was systematically investigated in situ by laser reflectance system and ex situ by morphology characterization, X-ray diffraction and X-ray photoelectron spectroscopy. It was found that InN can withstand isothermal annealing at temperature as high as 600 °C in NH 3 ambient. While in N 2 atmosphere, it will decompose quickly to form In-droplets at least at the temperature around 500 °C, and the activation energy of InN decomposition was estimated to be 2.1±0.1 eV. Thermal stability of InN when annealing in NH 3 ambient during temperature altering would be very sensitive to ramping rate and NH 3 flow rate, and InN would sustain annealing process at small ramping rate and sufficient supply of reactive nitrogen radicals. Whereas In-droplets formation was found to be the most frequently encountered phenomenon concerning InN decomposition, annealing window for conditions free of In-droplets was worked out and possible reasons related are discussed. In addition, InN will decompose in a uniform way in the annealing window, and the decomposition rate was found to be in the range of 50 and 100 nm/h. Hall measurement shows that annealing treatment in such window will improve the electrical properties of InN.

Mechanism investigation of NiOx in Au/Ni/p-type GaN ohmic contacts annealed in air

Recently, Au/Ni/p-type GaN ohmic contacts annealed in an air ambient have been widely investigated. However, to obtain a low specific-contact resistance, the annealing window is limited. In this study, to understand the oxidation function of metallic Ni, the Au/Ni/p-type GaN structure was annealed in an air ambient for 10 min at various temperatures. Using x-ray photoelectron spectroscopy (XPS) analysis, the metallic Ni was oxidized into NiO and NiO1.3 compositions at annealing temperatures of 500°C and 600°C, respectively. However, metallic Ni still existed on the interface of the Ni/p-type GaN annealed at 400°C. The associated barrier heights of 0.42 eV, 0.21 eV, and 0.31 eV were obtained with p-type GaN for the Ni, NiO, and NiO1.3 contacts, respectively. The hole concentrations of p-type NiO and p-type NiO1.3 were 2.6×1016 cm−3 and 2.0×1018 cm−3, respectively. The lower hole concentration of the p-type NiO would lead to reducing the valence-band bending of the p-type GaN, as well as the barrier height for holes crossing from the p-type NiO to the p-type GaN. The formation of NiO was thus an important issue for lowering the specific-contact resistance of the Au/Ni/p-type GaN ohmic contacts annealed in an air ambient.

Tantalum Nitride Films Grown by Inorganic Low Temperature Thermal Chemical Vapor Deposition Diffusion Barrier Properties in Copper Metallization

Key findings are presented from a systematic study which evaluated the performance of chemical vapor deposited (CVD) nitrogenrich tantalum nitride films as a diffusion barrier in copper (Cu) based metallization schemes. For this purpose, 3800 Å thick Cu films were grown by physical vapor deposition (PVD) on 550 Å thick films which were deposited by low temperature (<425°C) thermal CVD (TCVD) using tantalum pentabromide , ammonia, and hydrogen as coreactants. The resulting stacks were annealed in argon ambient at 450, 500, 550, and 650°C for 30 min each, along with similar PVD Cu/PVD bilayers of identical thickness. Both types of pre‐ and postannealed stacks were characterized by X‐ray photoelectron spectroscopy, Auger electron spectroscopy, Rutherford backscattering spectrometry, nuclear reaction analysis for hydrogen profiling, X‐ray diffraction, stack sheet resistance measurements, and Secco chemical treatment and etch‐pit observation by scanning electron microscopy. The resulting findings showed that the PVD films provided an excellent barrier against Cu diffusion throughout the annealing window investigated. Alternatively, the TCVD films exhibited similar stability up to 550°C. Barrier failure occurred, however, at temperatures between 550 and 600°C, as revealed by the formation of etch pits after Secco etch treatment. The failure of the TCVD films could not be attributed to bromine incorporation, given that residual bromine (∼0.5 atom %) in the TCVD films was highly stable against thermal diffusion in the temperature window investigated. Instead, the higher thermal stability of the PVD was attributed to differences in film microstructure and crystalline phase, or the location of excess nitrogen within the film matrix. © 1999 The Electrochemical Society. All rights reserved.

Deep Level Characterization and Passivation in Heteroepitaxial Inp

AbstractDeep levels in MOCVD grown p-InP on GaAs substrates have been investigated by Deep Level Transient Spectroscopy (DLTS). The effect of hydrogenation on the electrical activity of these levels has been studied through a combination of DLTS and Photoluminescence (PL) measurements. DLTS measurements indicate a drop of trap density from σ 5 × 1014 cm−3 to σ 1 × 1012 cm−3 after hydrogenation. Annealing at 400°C reactivated only the dopants, while temperatures above 600°C were necessary for deep-level reactivation. This combined with a logarithmic dependence on fill pulse time, indicate that at least one broad DLTS peak is associated with dislocations. The PL the DLTS results show that the dislocation related traps are passivated by hydrogen, preferentially over the dopants and that a wide annealing window exists for dopant reactivation.