Defects In Films Research Articles

Multifunctional and multi-site interfacial buffer layer for efficient and stable perovskite solar cells

Perovskite solar cells (PSCs) have achieved significant success in power conversion efficiency (PCE) and stability. However, interfacial recombination and film defects still hinder the improvement of PSCs efficiency. In this study, we propose a novel interfacial buffer layer material called Ethyl p-nitrobenzoate (EPN) to enhance device performance and stability. Our results demonstrate that introducing EPN improves the film's quality, reduces defect density, relieves interfacial stress, and significantly suppresses nonradiative recombination at the interface. Density functional theory (DFT) calculations confirm that EPN can effectively passivate defects in the perovskite and SnO2 films due to its multifunctionality. Finally, we achieved a high PCE of 23.16% for the target device while significantly enhancing device stability compared to the control. This work provides new insights into the development of multifunctional multi-site interfacial buffer layers for high-performance PSCs.

Mechanisms of conductive filament formation in hafnium oxide multilayer structures

The paper describes an investigation of resistive switching in the Pt/HfO2/HfOxNy/TiN, Pt/HfO2/TaOxNy/TiN, and Pt/Al2O3/HfO2/TaOxNy/TiN structures with oxide layers deposited by atomic layer deposition. Using conductive atomic force microscopy, we demonstrate the formation of conductive filaments in every structure. We also perform a complete resistive switching cycle. We define the properties of the filaments formed at different voltages and present the size and conductivity distributions of the filaments. Our research confirms that filaments in amorphous hafnium oxide initiate on the film defects, however, defects at different materials interfaces can enhance filament density in structures with different oxide layers. It appears that among the presented structures, the Pt/Al2O3/HfO2/TaOxNy/TiN structure has the greatest potential for use in resistive random-access memory.

Defects in Pyrochlore Dy2Ti2O7 Thin Film.

Defects in Pyrochlore Dy2Ti2O7 Thin Film.

Modulating Crystallization and Defect Passivation by Butyrolactone Molecule for Perovskite Solar Cells.

The attainment of a well-crystallized photo-absorbing layer with minimal defects is crucial for achieving high photovoltaic performance in polycrystalline solar cells. However, in the case of perovskite solar cells (PSCs), precise control over crystallization and elemental distribution through solution processing remains a challenge. In this study, we propose the use of a multifunctional molecule, α-amino-γ-butyrolactone (ABL), as a modulator to simultaneously enhance crystallization and passivate defects, thereby improving film quality and deactivating nonradiative recombination centers in the perovskite absorber. The Lewis base groups present in ABL facilitate nucleation, leading to enhanced crystallinity, while also retarding crystallization. Additionally, ABL effectively passivates Pb2+ dangling bonds, which are major deep-level defects in perovskite films. This passivation process reduces recombination losses, promotes carrier transfer and extraction, and further improves efficiency. Consequently, the PSCs incorporating the ABL additive exhibit an increase in conversion efficiency from 18.30% to 20.36%, along with improved long-term environmental stability. We believe that this research will contribute to the design of additive molecular structures and the engineering of components in perovskite precursor colloids.

Microstructure, mechanical, and electrochemical properties of Si/DLC coating deposited on 2024-T3 Al alloy

This work evaluated the microstructure, mechanical, and electrochemical properties of Si/DLC coatings deposited using ‎ the plasma-enhanced chemical vapor deposition (PECVD) technique. Tetramethylsilane and acetylene were used as precursor gases in the deposition process. The characteristics of the coating were estimated using different techniques. The corrosion performance was evaluated using various electrochemical methods in 3.5 wt% NaCl solution. The XPS analysis revealed that the film consists of Si and (a-C: H). The results revealed that as the deposition time increased, the hardness and Young's modulus decreased from 15.83 to 14.21 GPa and 125.8–114.9 GPa, respectively, while the thickness and adhesion strength increased. Moreover, the anti-corrosion ability of the DLC has been improved. It was found the corrosion potential moved to more noble direction (−618 to −562 mVAg/AgCl) while the corrosion rate decreased from 0.012 to 0.001 mmy−1. This trend can be attributed to growing coating thickness and fewer film defects which operated as a protective barrier against the corrosive solution. A failure mechanism of Si/DLC film has been suggested.

Surface passivation of CsPbBr3 films by interface engineering in efficient and stable self-powered perovskite photodetector

All-inorganic metal halide perovskite is considered as one of the most promising perovskite materials for photodetectors, because of its remarkable optoelectronic characteristics and stability. Whereas, it remains challenge to achieve both excellent photodetection performance and stability due to the multitudes of defects in perovskite films. Herein, an interface engineering based on surface passivation strategy to achieve high-quality CsPbBr3 perovskite films by introducing thioacetamide (C2H5NS, abbreviated as TAA) as interface materials is reported. The interaction between TAA and perovskite passivates the uncoordinated Pb2+ on the surface of CsPbBr3 film, suppress carrier non-recombination and accelerates carriers transfer. The self-powered photodetector based on the passivated CsPbBr3 film prefers the maximum responsivity of 0.26 A W−1 and detectivity of 8.39 × 1012 Jones under 520 nm irradiation. In addition, the optimized photodetector exhibits excellent stability and maintains more than 98% of its initial photocurrent when operating over 8 h. This work demonstrates an alternative approach for the preparation of improved performance in CsPbBr3 perovskite photodetectors and associated photoelectric devices.

Strengthened Surface Modification for High-Performance Inorganic Perovskite Solar Cells with 21.3% Efficiency.

Metal halide inorganic perovskites show excellent thermal stability compared to organic-inorganic perovskites. However, the performance of inorganic perovskite solar cells (PSCs) is far from theoretical values, together with unsatisfactory stability, mainly due to the poor interfacial properties. In this work, a facial but effective method is reported to realize high-performance inorganic PSCs by post-modifying the perovskite surface with 2-thiophene ethylamine (TEA). It is found that amine group from TEA can favorably interact with the undercoordinated Pb2+ via Lewis acid-based coordination, while thiophene ring with electron-rich sulfur assists such interaction by functioning as an electron donor. The synergetic interaction allows TEA to passivate perovskite film defects more efficiently, as compared to phenethylamine (PEA) with less electron-donating ability. Moreover, perovskite valence band is slightly upward shift to match with hole transport material and facilitate hole transfer. These combinations result in a reduced non-radiative charge recombination and improved charge carrier lifetime. Consequently, PSCs with TEA modification shows a drastic improvement of VOC by 54mV, yielding a champion PCE of 21.3%, much higher than the control PSCs (19.3%), along with improved ambient stability. This work demonstrates that surface modifier with an electron-rich moiety is critical for achieving efficient and stable inorganic PSCs.

A Multifunctional Additive Strategy Enables Efficient Pure-Blue Perovskite Light-Emitting Diodes.

Lead halide perovskites have shown exceptional performance in light-emitting devices (PeLEDs), particularly in producing significant electroluminescence in sky-blue to near-infrared wavelengths. However, PeLEDs emitting pure-blue light at 465-475 nm are still not satisfactory. Herein, efficient and stable pure-blue PeLEDs are reported by controlling phase distribution, passivation of defects, as well as surface modifications using multifunctional phenylethylammonium trifluoroacetate (PEATFA) in reduced-dimensional p-F-PEA2 Csn-1 Pbn (Br0.55 Cl0.45 )3n+1 polycrystalline perovskite films. Compared with 4-fluorophenylethylammonium (p-F-PEA+ ) in the pristine films, phenylethylammonium (PEA+ ) has lower adsorption energy while interacting with perovskites, resulting in large-n low-dimensional perovskites, which can greatly facilitate charge transport within the low-dimensional perovskite films. The interaction between the CO group in trifluoroacetate (TFA- ) and perovskites significantly reduces defects in the perovskite films. Additionally, the electron-giving CF3 group in TFA- uplifts surface potential in the films, resulting in smooth electronic injection in devices. The multifunctional additive strategy leads to elevated radiative recombination and efficient carrier transport in the films and devices. As a result, the devices exhibit a maximum external quantum efficiency (EQE) of 11.87% at 468 nm with stable spectral output, the highest reported to date for pure-blue PeLEDs. Thus, this study extends the way for high-efficiency pure-blue LED with perovskite polycrystal films.

Understanding optical and structural properties of the CH3NH3PbI3 nanocrystal thin films under humidity conditions

Low-dimensional organic-inorganic hybrid perovskite materials have drawn a lot of interest in optoelectronic applications because of their unique optoelectronic performance in comparison to their bulk counterparts. There is an influence of humidity conditions on the stability of perovskite in both positive and negative ways. The passivation of surface and bulk defects in the thin film of perovskite by the H2O molecules is a positive way. The negative way is that the material's stability will hinder the commercialization of perovskite-based devices. Herein, CH3NH3PbI3 nanocrystals are synthesized by the hot-injection method. The optical and structural properties of the thin film of the synthesized nanocrystals under different humidity conditions are studied through photoluminescence (PL), TRPL, Raman, X-ray diffraction (XRD), UV–Vis, spectroscopic ellipsometry, and FTIR techniques for 4 weeks. The redshift in the PL spectra of the thin film with an increase in PL intensity and carrier lifetime is caused by the shallow trap-assisted radiative recombination and localization of the charge carriers at the interface of the CH3NH3PbI3/water. The XRD, Raman, and FTIR peaks of the thin film are also shifted due to defect formation and structure distortion of the CH3NH3PbI3 crystal lattice. The thin films of these nanocrystals exhibit very high PLQY of 56% and 60% after 5 h and 1 week respectively. The results pave the way to analyse the stability of CH3NH3PbI3 nanocrystals through their optical and structural behaviour under different humidity conditions. The results also reflect that the photoemission of the synthesized material can be tuned by regulating the defect density and the structural deformation of the nanocrystals under controlled humidity conditions.

Multilateral Passivation Strategy in Post-Synthetic Flexible Metal-Organic Frameworks for Enhancing Perovskite Solar Cells.

The photovoltaic performance of perovskite solar cells is severely limited by the innate defects of perovskite films. Metal-organic framework (MOF)-based additives with luxuriant skeleton structures and tailored functional groups show a huge potential to solve these problems. Here, a multilateral passivation strategy is performed by introducing two alkyl-sulfonic acid functionalized MOFs, MIL-88B-1,3-SO3H and MIL-88B-1,4-SO3H, respectively, obtained from MIL-88B-NH2 through a post-synthetic process, for coordinating the lead defects and inhibiting non-radiative recombination. The flexible MIL-88B-type frameworks endow both functionalized MOFs with excellent electrical conductivity and preferable carrier transport in the hole-transport materials. Compared with the original MIL-88B-NH2 and MIL-88B-1,4-SO3H, MIL-88B-1,3-SO3H exhibits optimal steric hindrance and multiple passivation groups (-NH2, -NH-, and -SO3H), achieving the champion doped device with an enhanced power conversion efficiency (PCE) of 22.44% and excellent stability, which maintains 92.8% of the original PCE under ambient conditions (40% humidity and 25 °C) for 1200 h.

Corrosion protection of folic acid and lauric acid modified films prepared by anodic oxidation on WE43 magnesium alloys

The corrosion protection of folic acid (FA) and lauric acid (LA) modified films prepared by anodic oxidation on WE43 magnesium alloys was particularly evaluated by scanning electron microscopy (SEM), electron probe microanalysis (EPMA), static contact angle (CA) and electrochemical tests. The combined results of SEM and EPMA showed that both FA and LA penetrated into the cavities and cracks to repair the defects of the anodic films. The polarization resistance of the FA-modified films increased by 1.56 × 105 Ω cm2 and the LA-fmodified films showed the largest value (6.36 × 106 Ω cm2). They improved by two and three orders of magnitude compared with the substrate, which objectively revealed the excellent corrosion resistance capacity of the modified films on measurement results level. The CA results indicated that the obtained anodic films modified by LA were hydrophobic. Furthermore, the process of the organic modification sealing and the corrosion protection mechanism of the anodic films modified by FA and LA were discussed.

Improving stability and efficiency of three-dimensional perovskite solar cells with organophosphorus ligands

The core density of the defects in perovskite thin films will directly affect the properties of perovskite solar cells. On the other hand, interface engineering is usually being used to effectively improve the quality of perovskite thin films. In this sought of work, MAPbI3 perovskite thin films were modified by an antisolvent process using trioctylphosphine as a passivator. Trioctylphosphine is a kind of Lewis base and from the experimental results, it is noticed on being contribute to MAPbI3 grain growth and grain boundary passivation. Due to the grain boundary passivation and grain size increase, the intense defect density inside the grain and at the grain boundary of the MAPbI3 films is gradually reduced, thereby improving the carrier lifetime, while the hydrophobic property of octyl alkane makes the perovskite thin films less susceptible to air, water and oxygen degraded by the influence. The solar cell which are using the proposed films with the device structure configuration as ITO/SnO2/MAPbI3/spiro-OMeTAD/Ag and the perovskite layers were modified with trioctylphosphine. Among them, the perovskite thin films showcased to have a best performance when the trioctylphosphine chlorobenzene solution was about 0.15% and the PCE of the device reached for about 12.17%, an increase of 10% was compared with the standard device. In addition, the modified device exhibits good environmental stability, retaining about 90% of the initial efficiency for 100 h in a 70% humidity environment.

Effective passivation via additive engineering based on CsPbBr3 films photodetectors and image sensor application

All-inorganic perovskite photodetectors aroused widespread attention due to the splendid photoelectric characteristics and stability. However, the inherent defects in perovskite films hinders the progress of the photodetectors. Here, a Lewis base of thioacetamide additive was used to passivate defects in CsPbBr3 perovskite films based on Lewis acid-base interactions. The quality of the film has been distinctly enhanced due to the interaction between the S donor in thioacetamide and the uncoordinated Pb2+ in perovskite, diminishing the defect state density and inhibits the non-radiative recombination. The self-powered champion device based on CsPbBr3 film contain optimum thioacetamide additive exhibits a lower dark current density of 4.01 nA/cm2, a peak responsivity of 0.39 A/W, a rapid rise/decay time of 12.4 μs/56.2 μs, a peak detectivity of 1.08 × 1013 Jones and a lager linear dynamic range of 99 dB, which are much better than photodetector based on CsPbBr3 perovskite without TAA additive. Furthermore, it exhibits high-resolution imaging sensing capability at zero bias. This research affords guidance for the performance improvement and application of all-inorganic perovskite photodetectors.

Passivating CsPbBrxI3−x quantum dots via modifiers film to achieve efficient red light-emitting diodes

Although CsPbBrxI3−x quantum dots (QDs) have wide prospects for application in red light-emitting diodes (LEDs) due to their superior optoelectronic properties, the presence of defects and insulating long-chain ligands severely limits their luminescence performance. A novel strategy of spinning-coated CsPbBrxI3−x QDs on a PEABr or PEAI modified layer is designed to obtain red LEDs with efficient performance. The systematic studies on the structural evolution and optoelectronic properties of CsPbBrxI3−x QDs are discussed. The structural stability and electrical conductivity of CsPbBrxI3−x QDs are significantly improved because the halogen vacancies and insulating long-chain ligands (oleic acid and oleylamine) in CsPbBrxI3−x QDs are passivated and replaced by halogens and short-chain PEA from PEAX (X = Br and I), respectively. Modifying PEABr and PEAI obviously enhances the maximum external quantum efficiency (EQEmax) of CsPbBrxI3−x LEDs from 1.6 % to 11.7 %, and 14.9 %, respectively. Additionally, the electroluminescence (EL) spectral stability and useful life of LEDs are also ameliorated. The interfacial layer formed by the modified solution during the fabrication process of LEDs can effectively passivate the defects in QD films and improve the performance of LEDs. This preparation method is simple and easy to operate, which facilitates the design of efficient and stable QD-LEDs.

Two Specific Behaviors of Breakdown Occurrence Depending on N2 Annealing Temperature in Poly-Si/SiN/Poly-Si Capacitors

A time-dependent dielectric breakdown assessment was performed on a poly-Si/SiN/poly-Si capacitor to investigate the dependence of the breakdown occurrence on the N2 annealing temperature. We identified two specific behaviors of the breakdown occurrence dependent on the N2 annealing temperature: a peak at around 900 °C and a monotonic increase at temperatures above 1000 °C. Electron spin resonance spectroscopy was used to observe defects in the SiN film on the Si substrate, and the two behaviors showed good correlations with two types of changes in the defect densities: Pb centers on the Si substrate at the SiN/Si interface and an unidentified spectrum showing a local maximum at 900 °C; and E′ centers in the SiO2 film at the SiN/Si interface and K centers in the SiN film showing a monotonic increase at higher temperatures. We propose that the two specific behaviors of breakdown occurrence can be attributed to not only bulk defects in the SiN film but also defects near the SiN/Si interface.

Influence of Exposure Cd1-xMgx Fe₂O4 Compound by RF Plasma

Background:
 The work focuses on enhancing the structural properties, where the Cd1-x Mgx Fe2O4 products prepared by sol-gel solution were characterized. Auto ignition approach using several automated equipment, as FESEM, XRD, for concentrations (x=0.0,0.8 and 1), post-synthesis plasmas were exposed in a low-pressure chamber using the RF Magnetron Sputtering System and the results compared. by X-ray diffraction analysis, confirms the configuration to the FCC cubic structure of the studied samples. Plasma treatment did not affect the crystallization but the crystal size (D) of the particle size decreases after exposure to plasma from (32.33- 27.083)nm . Morphological studies confirmed surface shape changes and particle size reduction upon exposure to plasma.
 Materials and Methods:
 The sol-gel method common and old a chemical process for the production of a variety of nanostructures, most notably nanoparticles of metal oxide. In which The molecular feedstock is combined with water or alcohol and then subjected to moderate heating while being agitated. The basic principle pertaining to the sol-gel technology is to manufacture a homogenous solution created from raw materials also then gelatinized . The powders are ground and sintered in a refractory oven at 1100 ° C for 6 hours. The powder was then pressed by a hydraulic press at a pressure of 150 kN into molds to form a disc with a diameter of 20 mm. The work will take place in two phases: before exposing it to the plasma, and then when the samples are placed into the RF Magnetron Sputtering.
 Results:
 The X-ray measurements showed that the un-exposure and plasma- exposure samples have a cubic spinel structure, and that the variation of the structural parameters with the exposure is irregular, Consequently enhancing the atoms' ability to diffuse after being put onto the substrate and grain size of the sample. The morphological analysis of the as-prepared ferrite Cd1-xMgxFe2O4 samples was performed using FE-SEM, which gives details on the size and structure of the particles that make up the nanocrystals. The surface exposed to the plasma shows a change in the positions of the crystals and their cohesion with each other , which may result from a decrease in supermagnetic effect and lattice defects in Ferrite nanocrystalline films.
 Conclusion:
 The aim of this work is to synthesize Cd1-xMgx Fe₂O4 ferrite nanoparticles in spinel cube structure by sol-gel self-combustion method. Then, the synthesis of thermal plasma using Radio frequency (RF) plasma, where the structural properties, surface shape, and interpretation were studied properties of ferrite nanoparticles produced before and after plasma exposure. According to the conducted XRD investigations the validity of the cubic spinel structure of ferrite and that the irregular difference in the size of the crystals before and after the exposure, the particle size decreases after exposure to plasma from (32.33- 27.083)nm, and the capillary parameter they were reduced from (8.892 to 8.743)nm for plasma-treated samples. the results obtained from shaping cubic spinel phase in both iron nanoparticles before and after plasma exposure supported by the XRD results. The morphological study revealed irregularity grain distribution and dominant agglomeration in ferrite before and after exposure.

Design of an Ultra-Thick Film and Its Friction and Wear Performance under Different Working Conditions

Tantalum (Ta)/Ti/TiN/Ti/diamond-like carbon (DLC) (referred to as TTTD film) and Ta/Ti/TiN/TiCuN/Ti/DLC (referred to as ultra-thick film) films were designed in this study, and the factors affecting the friction and wear properties of DLC films in sodium bicarbonate and lactic acid solutions were analyzed. Moreover, a thin film with a thickness exceeding 50 microns was prepared. Morphology and tribological and mechanical properties were analyzed by scanning electron microscopy, friction and wear testing machine, and nanoindentation instrument, respectively. The results show that the presence of a TiCuN interlayer increases the defects in the DLC film and the roughness of surface, reaching a roughness of 0.19 µm. Compared with the TTTD film, the TiCuN interlayer reduces the hardness and increases the residual stress, which is 0.52 Gpa and −6.08 GPa, respectively. The TTTD film has a smooth and dense surface structure and high hardness, causing it to more easily form boundary lubrication. However, the ultra-thick film has lower hardness and rough surface, which cannot effectively form boundary lubrication. Therefore, the friction coefficient of the ultra-thick film is higher than that of the TTTD film under different working conditions. In sodium bicarbonate solution, a double-hydrolysis reaction is more likely to occur, resulting in a higher friction coefficient than in lactic acid solution. The friction coefficient of the TTTD film has a longer running-in period, which is attributed to the oxides generated by the double-hydrolysis reaction and the precipitated sodium bicarbonate crystals. Finally, it was concluded that the surface quality and the internal bond structure of DLC film have a significant impact on the friction and wear properties. This provides a theoretical basis for the design of multilayer structures.

Improving efficiency of n–i–p perovskite solar cells enabled by 3-carboxyphenylboronic acid additive

In the past period of time, perovskite solar cells have gained tremendous developments in improving photovoltaic performance, but they still face severe challenges. Defects in perovskite layers, especially at grain boundaries, severely limit the stabilization and efficiency of solar cells. In this work, we adopt 3-carboxyphenylboronic acid (CPBA) for modifying defects in perovskite thin films. Through the interaction among the carboxyl group, boronic acid and lead ions in the perovskite film, the crystallization effect of the perovskite molecular is greatly optimized. Moreover, the film defects are spontaneously passivated and the band gap is reduced, increasing the open circuit voltage and fill factor. Therefore, power conversion efficiency has been increased from 17.25% to 20.20%. This discovery provides a potential strategy for passivating the trap states in perovskite and enhancing the properties of devices.

Enhancing the Performance of Perovskite Solar Cells by Introducing 4-(Trifluoromethyl)-1H-imidazole Passivation Agents.

Defects in perovskite films are one of the main factors that affect the efficiency and stability of halide perovskite solar cells (PSCs). Uncoordinated ions (such as Pb2+, I-) act as trap states, causing the undesirable non-radiative recombination of photogenerated carriers. The formation of Lewis acid-base adducts in perovskite directly involves the crystallization process, which can effectively passivate defects. In this work, 4-(trifluoromethyl)-1H-imidazole (THI) was introduced into the perovskite precursor solution as a passivation agent. THI is a typical amphoteric compound that exhibits a strong Lewis base property due to its lone pair electrons. It coordinates with Lewis acid Pb2+, leading to the reduction in defect density and increase in crystallinity of perovskite films. Finally, the power conversion efficiency (PCE) of PSC increased from 16.49% to 18.97% due to the simultaneous enhancement of open-circuit voltage (VOC), short circuit current density (JSC) and fill factor (FF). After 30 days of storage, the PCE of the 0.16 THI PSC was maintained at 61.9% of its initial value, which was 44.3% for the control device. The working mechanism of THI was investigated. This work provides an attractive alternative method to passivate the defects in perovskite.

Precursor Solution Aging: A Universal Strategy Modulating Crystallization of Two-Dimensional Tin Halide Perovskite Films

Two-dimensional (2D) tin (Sn2+)-based perovskites have achieved remarkable advancements in (opto)electronic devices. However, fabricating high-quality and reproducible Sn halide perovskite thin films remains challenging due to uncontrollably fast crystallization. To overcome this issue, dimethyl sulfoxide has been incorporated as an indispensable strategy to form Lewis acid–base adducts but also has been proven to induce an irreversible Sn2+ oxidization effect. As the crystalline films grow directly from solution, a better understanding of precursor colloidal chemistry and the film formation process is critical. In this study, we report a universal solution aging approach to fabricate high-quality and reliable 2D Ruddlesden–Popper and Dion–Jacobson Sn2+ perovskite films and devices. The proper solution aging stabilizes the precursor colloids by eliminating aggregated complex and unreacted precursor clusters in the fresh precursor, leading to homogeneous nucleation/crystallization and film growth. The precursor aging reduced film defect density by nearly 2 orders of magnitude and improved charge transport mobility by over 5 times. This study can inspire the community to understand the deposition mechanism for high-quality Sn2+ perovskite thin films and promote the development of high-performance and reproducible Sn2+ perovskite based (opto)electronic devices.