Thermal Annealing Treatment Research Articles

Miscibility Regulation and Thermal Annealing Induced Hierarchical Morphology Enables High‐Efficiency All‐Small‐Molecule Organic Solar Cells Over 17%

AbstractAchieving an ideal morphology to realize efficient charge generation and transport is an imperative avenue to improve the photovoltaic performance of all small‐molecule organic solar cells (SM‐OSCs). Here, ternary SM‐OSCs are fabricated based on a new small molecule donor, SM‐mB, and an alloyed blend acceptor of Y6 and its derivative, L8‐BO, and desirable hierarchical morphology with appropriate nanoscale phase separation is successfully realized through adjusting the thermal annealing treatment conditions and compositions of mixed acceptors in the active layer. Then the ternary SM‐OSCs achieve an excellent PCE of 17.06 %, which is one of the best results for the SM‐OSCs so far. The desirable morphology can be ascribed to the optimization of the miscibility‐driven donor and acceptor blend morphology that takes full advantage of the individual advantages of both acceptors, which facilitate efficient charge generation and extraction with more balanced charge carrier mobilities. More importantly, the photovoltaic performance of the ternary SM‐OSCs possesses a high tolerance to the device fabrication conditions, including thermal annealing treatment, and is insensitive to film thickness, which is beneficial for large‐area manufacture and future practical applications.

External Fields Assisted Highly Efficient Oxygen Evolution Reaction of Confined 1T-VSe2 Ferromagnetic Nanoparticles.

As a clean and effective approach, the introduction of external magnetic fields to improve the performance of catalysts has attracted extensive attention. Owing to its room-temperature ferromagnetism, chemical stability, and earth abundance, VSe2 is expected to be a promising and cost-effective ferromagnetic electrocatalyst for the accomplishment of high-efficient spin-related OER kinetics. In this work, a facile pulsed laser deposition (PLD) method combined with rapid thermal annealing (RTA) treatment is used to successfully confine monodispersed 1T-VSe2 nanoparticles in amorphous carbon matrix. As expected, with external magnetic fields of 800 mT stimulation, the confined 1T-VSe2 nanoparticles exhibit highly efficient oxygen evolution reaction (OER) catalytic activity with an overpotential of 228mV for 10mA cm-2 and remarkable durability without deactivation after >100h OER operation. The experimental results together with theoretical calculations illustrate that magnetic fields can facilitate the surface charge transfer dynamics of 1T-VSe2 , and modify the adsorption-free energy of *OOH, thus finally improving the intrinsic activity of the catalysts. This work realizes the application of ferromagnetic VSe2 electrocatalyst in highly efficient spin-dependent OER kinetics, which is expected to promote the application of transition metal chalcogenides (TMCs) in external magnetic field-assisted electrocatalysis.

Thermal Annealing Triggered Chirality Inversion through Solvent Migration.

Solvent strategy is a powerful tool to manipulate chirality and self-assembly over hierarchical levels, yet the solvent dynamics during thermal annealing in controlling chirality and chiroptical features remain a mystery. Here, we show how solvent migration affects molecular folding and chirality through thermal annealing. Pyrene segments were conjugated to a 2,6-diamide pyridine skeleton, where intramolecular hydrogen bonds anchor the chiral geometry. The orientation of pyrene blades adopted π···π and CH···π stacking, respectively, in organic solvents (dimethyl sulfoxide, DMSO) and aqueous media, leading to the chiroptical inversion. Thermal annealing treatment of the DMSO/H2O mixture homogenized distribution of solvents that further altered the molecular folding from CH···π to π···π modality. Solvent migration from aggregates to bulky phases was evidenced by the nuclear magnetic resonance and molecular dynamic simulations, leading to the rearrangement of molecular packing with luminescent changes. It realized a consecutive chiroptical inversion using solvent strategy and thermal annealing.

Water-Assisted Ion Conduction in Solid-State Charge-Transfer Complex Electrolytes for Lithium Batteries

Current research on solid-state organic electrolytes mainly focuses on polymer electrolytes where ion transport is facilitated by chain segmental motion. A limited number of prior reports suggest that solid-state electrolytes based on organic charge-transfer (CT) complexes can have surprisingly high ionic conductivity. Here, we report that processing and environmental conditions drastically impact charge transport properties of CT complex electrolytes based on tetrathiafulvalene-tetracyanoquinodimethane (TTF-TCNQ) mixed with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). Thermal annealing and water vapor treatment decreases electronic conductivity and increases ionic conductivity. The electrolyte with a 1-1-2-0.45 molar ratio of TTF-TCNQ-LiTFSI-H2O has an ionic conductivity of 2 × 10–3 S/cm at 25 °C with order 104 times lower electronic conductivity. In this system where ion conduction is decoupled from the mobility of the organic phase, thermal annealing helps reduce CT connectivity and expose more surfaces to interact with LiTFSI, and water promotes the dissociation of LiTFSI.

Efficient non-fullerene organic solar cells employing aqueous solution-processed MoO3 as a hole-transporting layer

Organic solar cell (OSC) has drawn considerable interest in recent decades owing to their advantages of light weight, flexible, large area and potentially low-cost. Employing an appropriate hole-transporting layer (HTL) into an OSC device has been proved as an efficient method to obtain high efficiency OSC due to the enhancement of the hole transporting and extraction of the device. In this work, aqueous solution-processed MoO3 (s-MoO3) thin films were employed as HTLs to construct non-fullerene PM6:Y6 OSCs. The s-MoO3 thin film was prepared by using an aqueous solution process from an isopolymolybdate [NH4]6Mo7O24.4H2O precursor followed by thermal annealing treatment to convert the precursor to MoO3. The s-MoO3 HTL based PM6:Y6 device demonstrates a power conversion efficiency of 15.75%, which is 38% improved than that of the device with thermally evaporated-MoO3 as HTL and 8% improved than that of the device with PEDOT:PSS as HTL. The enhancement of the device performance could be attributed to the enhanced hole mobility and better band matching of the s-MoO3 HTL. Moreover, the s-MoO3 HTL based PM6:Y6 device exhibited higher device stability than those of the reference devices. Our finding indicates that this s-MoO3 film has great potential as efficient HTL for high performance non fullerene OSCs.

Effects of thermal annealing on the spin–orbit torque and unidirectional spin Hall magnetoresistance in Pt/CoFe/Ta trilayers

We investigated the spin–orbit torque (SOT) and unidirectional spin Hall magnetoresistance (USMR) in Pt/CoFe/Ta trilayer as well as Pt/CoFe and CoFe/Ta bilayers with in-plane magnetic anisotropy by performing transverse and longitudinal second harmonic resistance measurements. Compared to the two bilayers, we found that the trilayer exhibits enhanced SOT and USMR due to the opposite spin Hall angles of Pt and Ta, which work together to enhance the spin accumulation in the trilayer. Furthermore, we found that thermal annealing has a significant influence on the magnitude and sign of the SOT and USMR in the Pt/CoFe/Ta trilayers. Specifically, we observed that both the damping-like SOT and USMR of the trilayer decrease as the annealing temperature increases, and they even change signs at an annealing temperature between 235 and 265 °C. In contrast, the sign change of the SOT and USMR upon annealing is absent in the Pt/CoFe and CoFe/Ta bilayers. These findings suggest that the sign of the SOT and USMR in the Pt/CoFe/Ta trilayer can be easily manipulated by using an appropriate thermal annealing treatment, which has important implications for the development of novel spintronic devices.

Activation of Mg impurities in epitaxial p-GaN with rapid thermal annealing assisted supercritical fluid treatment

The activation of an Mg acceptor in p-GaN with rapid thermal annealing (RTA) assisted low-temperature supercritical fluid (SCF) treatment (RTA-A-SCF) was investigated. After RTA-A-SCF treatment, the luminescence band of the N vacancy in the PL spectra was significantly suppressed. An evident decrease in H concentration is also observed in secondary ion mass spectrometer measurements, it indicates an obvious decrease of Mg–H complexes in the p-GaN. In addition, the ohmic contacts have been well improved and the hole concentration has increased by an order of magnitude. The activation mechanism of RTA-A-SCF treatment was further analyzed by X-ray photoelectron spectroscopy.

Micro-/nano-scale structure and elemental diffusion in the Al/Ti/Al sandwich structure

To reveal the complexities of microstructures at the Al/Ti interface, Al/Ti/Al sandwich structures are produced through thermal pressing and annealing treatment. The multi-scale interface structures, elemental diffusion, grain characteristics, and micromechanics are investigated by scanning electron microscopy (SEM), electron back-scattered diffraction (EBSD), transmission electron microscopy (TEM), and nano-indentation. The results indicate only TiAl3 is generated at the interface, and the interlayer thickness and TiAl3 grain size increase with the rising temperature. On the microscale, a compact interlayer is visible at 500 and 550 °C, whereas massive Al-enriched bulks are dispersed in the interlayer as the temperature increases to 650 °C. Abnormal micro-defects at 600 and 650 °C are partially formed with the thickening of the interlayer and the segregation of Mg and Si. Unexpectedly, interfacial microvoids, amorphous layers, and oxides are detected, which hinder the growth of the interlayer. On the nanoscale, misfit dislocations and lattice distortions are observed at the interface. More interestingly, the Ti–Al solid solution structures with severe lattice misfits are generated on the three-dimensional (3D) Ti/TiAl3 interface, which is considered to be a novel strategy for enhancing the strength-plasticity synergy of composite structures.

Single Crystalline Transparent Conducting F, Al, and Ga Co-Doped ZnO Thin Films with High Photoelectrical Performance.

Transparent conductive film (TCF) is a material that integrates electrical conductivity and optical transparency. It is widely used as an electrode material in thin-film solar cells. However, considerable progress is needed to facilitate its high performance and low-cost preparation. In this study, a preparation scheme for AlF3 and GaF3 co-doped ZnO (FAGZO) thin films was designed and implemented by magnetron sputtering (MS). The mutual restraint between the electrical properties and the wide-spectrum transmission performance of ZnO films was resolved. First-principles calculations showed that the doped ZnO system had n-type conductivity and that the most stable structure was the FO-AlZn-GaZn system. The experimental results verified the theoretical predictions. Single crystalline ZnO transparent conducting films (ZnO-TCFs) of high quality were achieved by MS. After rapid thermal annealing (RTA) treatment, the mobility reached 49.6 cm2/V s, and the resistivity decreased to 3.82 × 10-4 Ω cm. The AT was 90% between 380 and 1200 nm. Furthermore, the application of the prepared FAGZO film in perovskite solar cells (PSCs) has been verified. Compared to the reference indium tin oxide film, the PSCs using the FAGZO film showed higher JSC and power conversion efficiency. These results demonstrate that MS combined with anion and cation co-doping provides an effective means of exploring high-quality and high-performance ZnO-TCFs.

Nickel(II) Nitrate Hole‐Transporting Layers for Single‐Junction Bulk Heterojunction Organic Solar Cells with a Record 19.02 % Efficiency

AbstractA facile strategy was developed here to improve the film quality of nickel‐based hole transporting layer (HTL) for efficient organic solar cell (OSC) applications. To prevent the agglomeration of Ni(NO3)2 during film deposition, acetylacetonate was added into the precursor solution, which led to the formation of an amorphous and glass‐like state. After thermal annealing (TA) treatment, the film‐forming ability could be further improved. The additional UV‐ozone (UVO) treatment continuously improved the film quality and increased the work function and conductivity of such HTL. The resulting TA & UVO modified Ni(NO3)2 & Hacac HTL produced highly efficient organic solar cells with exciting power conversion efficiencies of 18.42 % and 19.02 % for PM6 : BTP‐eC9 and D18 : BTP‐Th devices, respectively, much higher than the control PEDOT : PSS devices.

Nickel(II) Nitrate Hole-Transporting Layers for Single-Junction Bulk Heterojunction Organic Solar Cells with a Record 19.02 % Efficiency.

A facile strategy was developed here to improve the film quality of nickel-based hole transporting layer (HTL) for efficient organic solar cell (OSC) applications. To prevent the agglomeration of Ni(NO3 )2 during film deposition, acetylacetonate was added into the precursor solution, which led to the formation of an amorphous and glass-like state. After thermal annealing (TA) treatment, the film-forming ability could be further improved. The additional UV-ozone (UVO) treatment continuously improved the film quality and increased the work function and conductivity of such HTL. The resulting TA & UVO modified Ni(NO3 )2 & Hacac HTL produced highly efficient organic solar cells with exciting power conversion efficiencies of 18.42 % and 19.02 % for PM6 : BTP-eC9 and D18 : BTP-Th devices, respectively, much higher than the control PEDOT : PSS devices.

Valley-Polarized Interlayer Excitons in 2D Chalcogenide-Halide Perovskite-van der Waals Heterostructures.

Interlayer excitons (IXs) in two-dimensional (2D) heterostructures provide an exciting avenue for exploring optoelectronic and valleytronic phenomena. Presently, valleytronic research is limited to transition metal dichalcogenide (TMD) based 2D heterostructure samples, which require strict lattice (mis) match and interlayer twist angle requirements. Here, we explore a 2D heterostructure system with experimental observation of spin-valley layer coupling to realize helicity-resolved IXs, without the requirement of a specific geometric arrangement, i.e., twist angle or specific thermal annealing treatment of the samples in 2D Ruddlesden-Popper (2DRP) halide perovskite/2D TMD heterostructures. Using first-principle calculations, time-resolved and circularly polarized luminescence measurements, we demonstrate that Rashba spin-splitting in 2D perovskites and strongly coupled spin-valley physics in monolayer TMDs render spin-valley-dependent optical selection rules to the IXs. Consequently, a robust valley polarization of ∼14% with a long exciton lifetime of ∼22 ns is obtained in type-II band aligned 2DRP/TMD heterostructure at ∼1.54 eV measured at 80 K. Our work expands the scope for studying spin-valley physics in heterostructures of disparate classes of 2D semiconductors.

Thermal annealing effects on graphene/n-Si Schottky junction solar cell: removal of PMMA residues

Thermal annealing is one of the most effective ways to improve the efficiency of a graphene/n-Si Schottky junction solar cell. Here, its underlying mechanism has been investigated by comparative studies in terms of the removal of polymethyl methacrylate (PMMA) residues, using the J–V characteristics and transient photocurrent and photovoltage measurements. The obtained results have revealed that there are trap states that originate from the PMMA residues and cause the large photocurrent leakage as the intensity of the incident light increases. It is also found that the PMMA residues accelerate deterioration and rapidly invalidate hole doping effects. Such undesirable PMMA residues were effectively removed by the thermal annealing treatments, serving to reduce the photocurrent leakage and increase the stability.

Chemical Dopant-Free Controlled MoTe2/MoSe2 Heterostructure toward a Self-Driven Photodetector and Complementary Logic Circuits.

Two-dimensional (2D) van der Waals heterostructures based on transition metal dichalcogenides are expected to be unique building blocks for next-generation nanoscale electronics and optoelectronics. The ability to control the properties of 2D heterostructures is the key for practical applications. Here, we report a simple way to fabricate a high-performance self-driven photodetector based on the MoTe2/MoSe2 p-n heterojunction, in which the hole-dominated transport polarity of MoTe2 is easily achieved via a straightforward thermal annealing treatment in air without any chemical dopants or special gases needed. A high photoresponsivity of 0.72 A W-1, an external quantum efficiency up to 41.3%, a detectivity of 7 × 1011 Jones, and a response speed of 120 μs are obtained at zero bias voltage. Additionally, this doping method is also utilized to realize a complementary inverter with a voltage gain of 24. By configuring 2D p-MoTe2 and n-MoSe2 on demand, logic functions of NAND and NOR gates are also accomplished successfully. These results present a significant potential toward future larger-scale heterogeneously integrated 2D electronics and optoelectronics.

Fotovoltaik Hücrelerin Yüzey Morfolojisi ve Verimliliği Üzerinde Termal Tavlama Etkisi

Photovoltaics convert solar radiation into electrical current. For the present study, blends containing electron donor and acceptor are used instead of materials made with silicon. Carbon-based organic semiconductors are easy to process and have low fabrication costs. There are several fabrication steps playing important role in the photovoltaic device performance such as, substrate preparation, polymer-acceptor ratios in the blend, thermal annealing of the active layer and top electrode deposition. It has been shown that nanoscale morphology of the blend can be altered via thermal annealing treatment. As a result, efficiency is affected by surface roughness. The blend of P3HT: PCBM as donor: acceptor was used to fabricate thin films and photovoltaic cells. The power conversion efficiencies and surface morphologies of the devices annealed at various times were measured. Atomic force microscopy (AFM) images revealed that the surface roughness of the active layer is mainly affected by the annealing time, and the film with the roughest surface results in the most efficient solar cell.

The Effect of Post Deposition Treatment on Properties of ALD Al-Doped ZnO Films

In this paper, aluminum-doped zinc oxide (ZnO:Al or AZO) thin films are grown using atomic layer deposition (ALD) and the influence of postdeposition UV-ozone and thermal annealing treatments on the films' properties are investigated. X-ray diffraction (XRD) revealed a polycrystalline wurtzite structure with a preferable (100) orientation. The crystal size increase after the thermal annealing is observed while UV-ozone exposure led to no significant change in crystallinity. The results of the X-ray photoelectron spectroscopy (XPS) analyses show that a higher amount of oxygen vacancies exists in the ZnO:Al after UV-ozone treatment, and that the ZnO:Al, after annealing, has a lower amount of oxygen vacancies. Important and practical applications of ZnO:Al (such as transparent conductive oxide layer) were found, and its electrical and optical properties demonstrate high tunability after postdeposition treatment, particularly after UV-Ozone exposure, offers a noninvasive and easy way to lower the sheet resistance values. At the same time, UV-Ozone treatment did not cause any significant changes to the polycrystalline structure, surface morphology, or optical properties of the AZO films.

In-situ partial oxidation of TiVCTx derived TiO2 and V2O5 nanocrystals functionalized TiVCTx MXene as anode for lithium-ion batteries

Two-dimensional double transition metal carbides or nitrides (MXenes) have been commonly concerned in the field of energy storage due to their distinctive structure and high conductivity. MXene-based electrode materials with single metal component are difficult to achieve high specific capacity, efficient ion/electron transport and stability, which hinder its practical application. Herein, we proposed a strategy by using in situ partial oxidation of double transition metal MXene (TiVCTx) derived TiO2 and V2O5 nanocrystals blends functionalized TiVCTx MXene (for simplicity denoted as TiVC@VTO) as electrode materials to boost the lithium ion battery performance. Effect of annealing temperature on the microstructure, crystallinity, and electrochemical property of TiVC@VTO is investigated. The TiVC@VTO retains the layer structure of the original TiVCTx MXene and at the same time the composition and microstructure can be regulated by a simple thermal annealing treatment to modify the oxidation degree. Compared with pristine TiVCTx, the oxidized sample demonstrates an optimal performance with specific capacity of 331.1 mAh g−1 after 100 cycles at current density of 0.1 A g−1 and 237.6 mAh g−1 after 1000 cycles at current density of 1.0 A g−1 at 500 °C (TiVC@VTO-500). Our work offers a simple and practicable method for enhanced lithium-ion storage capability by using double transition metal MXene. Moreover, this work also provides further information about the stability of TiVCTx MXene, which will benefit energy storage in the future development of novel double transition metal MXene materials for energy storage applications.

Thermal Annealing Induced Surface Oxygen Vacancy Clusters in α-MnO2 Nanowires for Catalytic Ozonation of VOCs at Ambient Temperature.

Catalytic ozonation has gained considerable interest in volatile organic compound (VOC) elimination due to its mild reaction conditions. However, the low activity and mineralization rate of VOCs over catalysts hinder its practical application. Herein, a series of α-MnO2 nanowire catalysts were prepared via thermal annealing treatment at various temperatures to tailor defect species. Numerous characterization techniques were used and combined to investigate the relationship between activity and microstructure. PALS and XAFS indicated that more unsaturated manganese and oxygen vacancies, especially surface oxygen vacancy clusters, were produced in α-MnO2 under the optimal high calcination temperature. As a result, MnO2-600 was found to exhibit the best-ever performance in toluene conversion (95%) and mineralization rate (89.5%) at 20 °C, making it a promising candidate for practical use. The roles of these defects in manipulating the reactive oxygen species of α-MnO2 were clarified by quantifying the amounts of reactive oxygen species by quenching experiments and density functional theory calculations. 1O2 and ·OH species generated in the vicinity of oxygen vacancy clusters, especially the dimer oxygen vacancy cluster, were identified as key oxygen species in the abatement of toluene. This study provides a facile method to engineer the microstructure of MnO2 by means of the manipulation of oxygen vacancies and an in-depth understanding of their roles in the catalytic ozonation of VOC.

Fabrication of thin ferroelectric Hf0.5Zr0.5O2 films by millisecond flash lamp annealing

We used millisecond flash lamp annealing (FLA) to form thin ferroelectric Hf0.5Zr0.5O2 (HZO) films with thicknesses of less than 10 nm and with remanent polarization up to 30 μC cm−2. A clear dependency of the polarization on the annealing temperature and time was observed, indicating that the precise management of the thermal budget is a key factor in forming ferroelectric HZO. We also show and compare the process windows within which ferroelectricity in 10 and 5 nm samples is obtained. The results show that a high thermal budget is necessary for thinner samples. We examined the endurance characteristics and a greater endurance compared to rapid thermal annealing treatment was observed with more than 1010 cycles without breakdown confirmed in 5 nm thick samples. The data indicates that there is the possibility of further thickness scaling whilst retaining highly durable characteristics for films annealed by FLA.

Sulfonated polybenzimidazole engineering defect-induced N, S-codoped carbon-supported Co3C hybrid composite as high-efficiency electrocatalyst for oxygen evolution reaction

The exploitation of efficient OER electrocatalysts has become the key to realize the commercial-application of H2 production from electrocatalytic water splitting. In this research, the novel defect-induced N, S co-doped carbon-supported Co3C nanoparticles were successfully fabricated as OER electrocatalyst by combination of wet-impregnation treatment of Co/sulfonated polybenzimidazole (sPBI) and subsequent thermal annealing treatment, which was denoted as Co3C/CNS-X (X=700, 800, 900) electrocatalyst. Among them, Co3C/CNS-800 delivered the more favorable architecture due to its large specific surface area, high dispersion of Co3C nanoparticles and especially the generation of abundant defects sites, which not only improved its conductivity and the amounts of electrocatalytically active sites but also imparted the extremely important functionality in accelerating the interfacial electron-transfer and facilitated the adsorption ability of intermediates, thus exerting the extraordinary activities for catalyzing OER. What's more, there were some evidences demonstrating the generation of the strong interfacial interactions through the Co-N coordination bonds and the formation of more pyridinic-N species though annealing treatment, which allowed the structural stability to be further strengthened and simultaneously gave impetus to the O2 release for the reduction of OER overpotential. In recognition of these approvable structural characteristics, the Co3C/CNS-800 exhibited the lowest overpotential of 300 mV at an anodic current density of 10 mA cm−2, and a small Tafel slope of 70 mV dec−1 in 1 M KOH electrolyte as well as a long durability.