Thin Surface Research Articles

Effect of High Polymer, Crumb Rubber, and Epoxy-Modified Asphalt Binders on Laboratory Performance of Open-Graded Friction Course Mixtures

Open-graded friction course (OGFC) is a thin asphalt mixture surface layer. It is gap-graded with a high percentage of coarse aggregates that are nearly uniform in size, resulting in a high percentage of interconnected air voids and asphalt binder, which provides improved skid resistance, visibility, and decreased pavement–tire noise. However, construction personnel at the Louisiana Department of Transportation and Development reported that conventional OGFC mixtures have durability issues and shorter service life, compared with thin asphalt mixture lifts. Hence, effects of different asphalt binder types on the performance of OGFC mixtures were evaluated. Five types of asphalt binder were utilized: conventional styrene-butadiene-styrene (SBS) asphalt binder PG 76-22M; high SBS content asphalt binder PG 88-28; diluted epoxy asphalt (EA) binder with two different dosages (25% and 50%); and a hybrid modified asphalt binder prepared with SBS and crumb rubber modifier PG 76-22G. The optimal aggregate structures were determined based on minimum required air voids and voids in coarse aggregate. Physical and mechanical tests were conducted to assess the performance of OGFC mixtures, including draindown, permeability, loaded wheel track, and Cantabro abrasion loss. Results indicate that OGFC mixtures incorporating diluted EA binder exhibited lower draindown values than mixtures containing PG 76-22M and PG 88-28. Moreover, mixtures with PG 88-28 and 50% EA binders demonstrated improved resistance to rutting. Mixtures with 50% EA and PG 88-28 binders demonstrated improved durability, compared with mixtures with PG 76-22M for unaged and aged conditioning, as measured by Cantabro abrasion loss values.

Control of visible-range transmission and reflection haze by varying pattern size, shape and depth in flexible metasurfaces

Cost-effective soft imprint lithography technique is used to prepare flexible thin polymeric surfaces containing a periodic arrangement of nanodimples and nanobumps of sub-micron size. Using a single master mold of self-assembled colloidal crystal, metasurfaces with different depths and heights of patterns with a fixed pitch are possible, which makes the process inexpensive and simple. These metasurfaces are studied for their diffuse and total transmission and reflection spectra in the visible range. The transmission haze and reflection haze are calculated from the measurements. The surface containing nanobumps of lesser pattern height result in higher values of reflection and transmission haze than from surfaces containing nanodimples of much higher depth for the same pitch. The haze is more dependent on the pattern depth or height and less dependent on the pitch of the pattern. Far-field transmission profiles measured in the same wavelength range from the patterned surfaces show that the scattering increases with the increase of the ratio of pattern depth/height to pitch, similar to the haze measurements conducted with a closed integrating sphere. These profiles show that the angular spread of scattered light in transmission is within 10°, explaining the reason for the relatively low transmission haze in all the patterned surfaces. Simulation results confirm that the nanobump pattern gives higher transmission haze compared to nanodimple pattern. By controlling the ratio of pattern depth/height to pitch of the features on these surfaces, both an increase in optical haze and a balance between total reflection intensity and total transmission intensity can be achieved.Graphical

Copper doped hydroxyapatite nanocomposite thin films: synthesis, physico-chemical and biological evaluation.

Cu-doped hydroxyapatite (CuHAp) thin films were obtained using spin coating method. To make these thin films, CuHAp suspensions obtained by sol-gel method were used. The coatings obtained were thermally treated at 500°C. After the thermal treatment, the thin films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM). Moreover, the stability of the suspensions before being used to obtain the thin films was certified by dynamic light scattering (DLS), zeta potential methods and ultrasound measurements. In the XRD patterns, the peaks associated with hexagonal hydroxyapatite were identified in accordance with JCPDS no. 09-0432. EDS and XPS results confirmed the presence of Cu ions in the samples. Data about the morphological features and chemical composition of CuHAp thin films were obtained by performing scanning electron microscopy (SEM) measurements. Our results suggest that the CuHAp thin films surface is continuous and homogenous. The presence of the functional groups in the CuHAp thin films was confirmed by Fourier-transform infrared spectroscopy (FTIR) and Raman spectroscopy studies. Information about the surface topography of the CuHAp thin films has been obtained using atomic force microscopy (AFM). The AFM images determined that the surface topography of the CuHAp thin layer is homogenous and continuous without presenting any unevenness or fissures. The cytotoxicity of CuHAp thin films was assessed using human gingival fibroblasts (HGF-1) cells. The results of the cell viability assays demonstrated that the thin films presented good biocompatible properties towards the HGF-1 cells. Additionally, the adherence and development of HGF-1 cells on the surface of CuHAp thin films were determined using AFM. The AFM surface topographies highlighted that the CuHAp thin film's surface favored the attachment and proliferation of HGF-1 cells on their surface.

Characterization of alane (AlH3) thin films grown by atomic layer deposition for hydrogen storage applications

Alane (AlH3) is an increasingly favored material for hydrogen and energy storage. It has demonstrated its potential in various applications, including rocket fuel, explosives, reducing agents, and serving as a viable source of hydrogen for portable fuel cells. In this study, we present the fabrication, morphology and elemental characterization of an AlH3 thin film grown through atomic layer deposition using a dimethylethylamine alane (DMEAA; AlH3N(CH3)2(CH2CH3)) precursor. The AlH3 thin film exhibited a rough surface with a white-like appearance, forming coarse grains as observed via scanning electron microscopy. X-ray diffraction confirmed the presence of AlH3 and it was compared with an aluminum thin film. Energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy confirmed the presence of pure AlH3 under a very thin aluminum oxide surface layer. Additionally, we propose a dissociation reaction mechanism based on the DMEAA precursor. Our work contributes to the advancement of hydrogen storage materials and energy-related applications that necessitate high hydrogen storage capacity and energy efficiency.

Electronic structure and properties of activated Al0.5Ga0.5N thin films and nanowires photocathode surface adsorbed with residual gas

To study effect of residual gas in vacuum system on structure and electrical performance of activated AlGaN photocathodes, adsorption models for H2O, CO and CO2 adsorbed on Al0.5Ga0.5N activated surfaces are established and investigated. The results indicate that activated Al0.5Ga0.5N surfaces are not easily adsorbed by residual gases compared to pristine surface. For Al0.5Ga0.5N thin film, H2O and CO exhibit higher affinity for adsorption on Cs/NF3-activated surfaces, while CO2 shows greater tendency to adsorb on Cs-activated surface·H2O, CO and CO2 are most easily adsorbed on Cs/NF3-activated surface for Al0.5Ga0.5N nanowires. Work function of Cs/NF3-activated thin film surface is 2.34 eV, and after adsorbing H2O, CO and CO2, work functions are 1.84 eV, 2.37 eV, and 3.43 eV, respectively. This means that residual gas will increase work function and is harmful to quantum efficiency improvement.

Microfluidic mass transfer of supercritical CO2 in brine

In the context of carbon sequestration in saline aquifers, we investigate CO2 transport dynamics in brine under reservoir-like conditions (P = 8 MPa, T = 50∘C) using microfluidics. We quantify the mass transfer of supercritical CO2 in brine across a range of concentrations (0–1 M) and liquid flow rates (15–60 μL/min) for the first time. We find the volumetric mass transfer coefficient kLa ranges from 50.3 to 144.0 s−1, increasing with flow rate and, to a lesser extent, with salinity. More importantly, the kLa value for supercritical CO2 in brine at a higher temperature shows a significant enhancement of >50% compared to gas and liquid CO2 in water. Our analysis, incorporating a theoretical mass transfer model, points to a dominant contribution from the liquid film to the overall kLa, nearly doubling that of the emulsion caps, attributed to the thin film's larger surface area and dynamic renewal.

Divertor heat load estimates on NSTX and DIII-D using new and open-source 2D inversion analysis code

A thermography inversion algorithm has been developed in the open-source Python-based computer code, HYPERION, to calculate the heat flux incident on plasma-facing components (PFCs) in axisymmetric tokamaks. The chosen mesh size at the surface significantly affects the calculated transient heat flux results. The calculated transient heat flux will exceed the real value when the mesh size tends to zero but will underestimate the real value when the mesh size is large. A criterion for determining the appropriate mesh size for the transient heat flux calculation will be discussed. The numerical scheme for HYPERION uses a 2D fully implicit finite-difference approach, allowing temperature-dependent thermal properties of PFC materials. The inversion algorithm is benchmarked against established heat flux calculation codes, TACO and THEODOR, based on thermography data from NSTX and DIII-D respectively. The primary benefits of HYPERION compared to TACO and THEODOR are that it is open-source and it allows for the optimization of mesh thickness along the substrate. The algorithm also accounts for the thermal properties of thin surface layers that characteristically form on PFCs due to plasma-material interactions. The agreement between HYPERION and THEODOR is excellent, as the percent difference between the codes is ∼5% on average in the case of the DIII-D data for moderate to high heat flux. Verification tests with TACO show slightly higher average percent differences of 8% and 12%. In using HYPERION to study filaments in heat flux, the initial results indicate that small ELMs filaments significantly broaden the divertor heat flux, and decrease divertor peak flux. Compared to the inter-ELM, the small ELM filaments decrease the divertor peak surface temperature. With intermittent divertor filaments, the divertor heat flux width is comparable with that found in L-mode.

Liquid Metal Alloys Enable Efficient Formate Electrosynthesis

AbstractLiquid metals are an interesting class of materials with the unique combination of metallic nature and liquid fluidity, and have recently been explored in many emerging fields. Their potential applications in catalysis, unfortunately, remain largely untapped. Herein, Ga‐mediated liquid metal alloying as an effective strategy is demonstrated to prepare functional alloys for catalysis. The alloying is carried out by dissolving indium or tin pellets in liquid gallium at room temperature or assisted by gentle heating, giving rise to binary Ga1−xInx and Ga1−xSnx liquid metal alloys with tunable chemical compositions. When further subjected to ultrasonication in water, they are ruptured into nanosized particles with liquid metal cores and thin surface oxide shells. Electrochemical measurements reveal that the liquid metal alloying significantly promotes electrocatalytic CO2 reduction to formate. Taking Ga0.75In0.25 as an example, its formate Faradaic efficiency is enhanced by 10%–20% compared to those of Ga and In, and its formate partial current density is 4–6 times larger than those of Ga and In. This enhancement is rationalized via computational simulations showing that the surrounding of In active sites with Ga atoms deactivates the undesirable reaction pathways to CO or H2, and facilitates selective formate electrosynthesis.

A novel Se-diffused selenization strategy to suppress bulk and interfacial defects in Sb2Se3 thin film solar cell

In recent years, vacuum-based deposition of antimony selenide (Sb2Se3) thin films has garnered significant attention owing to its easy and impurity-free fabrication, along with exceptional power conversion efficiency (PCE). However, the necessary post-selenization process comes with a shortcoming of instigating buried Sb2Se3/molybdenum (Mo) back-contact interface defects. This study introduces a novel Se-diffusion post-selenization technique to precisely regulate the selenium reaction atmosphere, preventing void formation on the Sb2Se3 thin film surface and maintaining film quality for enhanced device efficiency. An optimized selenization condition with a precise Se precursor film thickness led to obtaining highly crystalline, preferentially (hk1) oriented, and large-grained Sb2Se3 films. Furthermore, a meticulous Se diffusion in Sb2Se3 film reduced the inevitable MoSe2 layer thickness at the Mo surface, thereby enhancing the quality of the back contact interface. The Sb2Se3 solar cell that was selenized to optimal level showed significant enhancements, raising the fill factor from 40.06 % to 45.12 % and improving the device efficiency from 2.89 % to 3.57 %. Our newly developed selenization strategy establishes a successful approach to regulate the Sb2Se3 film quality by addressing a crucial challenge in improving the efficiency of antimony chalcogenide solar cells.

Analysis of optical, structural, and morphological properties of a Ti-doped α-Fe2O3 thin film produced through RF and DC magnetron Co-sputtering

In this study, a Titanium (Ti) doped α-Fe2O3 (hematite) thin layer was synthesized onto a glass substrate, employing the simultaneous DC and RF magnetron sputtering method. The investigation focused on examining specific physical properties of the film. The optical, structural, morphological, and elemental features of the resulting Ti-doped α-Fe2O3 thin film were characterized using different characterization techniques. The XRD studies indicated a rhombohedral crystal structure in the studied thin film. The calculation of the Eg value for the thin film, based on absorption measurements, resulted in a value of 2.19 eV. Raman peaks were identified within the range of 218 cm−1 to 1300 cm−1. According to SEM images, the thin film exhibited a uniform surface morphology across the substrate. AFM images revealed a low root mean square (RMS) roughness value, indicating a smooth Ti:Fe2O3 thin film surface.

The Interaction and Lift-Off Forces of an Atomic Force Microscope Tip from Single Fibers Extracted from Protective Clothing Fabric.

The widespread use of engineered nanoparticles (ENPs) poses a potential health hazard to humans, especially to those involved in either nanoparticle manufacturing or the usage and assembly of a final product. In this study, we performed systematic force vs distance experiments (F(z)) using an atomic force microscope (AFM) on fibers commonly used in street clothing and protective laboratory clothing to better characterize the relevant interaction forces between engineered nanoparticles (ENPs) and the contacted fabric fibers. The intent of this study is to identify those factors that influence the interaction of ENPs with fabrics with an aim to improve the efficacy of protective clothing against ENP exposure and mitigate potential health risks. A ∼14 nm diameter AFM SiOx tip (with nanoscale radius of curvature) is considered as an effective oxide ENP. Features present (or absent) in a well-executed F(z) AFM experiment provide a fingerprint that distinguishes the relevant forces and interaction mechanisms in play. Measurements of F(z) as a function of relative humidity were also performed to assess the importance of thin surface water layers in binding nanometer-size oxide ENPs to a fabric fiber. The F(z) data indicate the dominant mechanism for adhesion of the oxide tip to the various fabric fibers (cotton, Tyvek (HD polyethylene), polypropylene, and polyester) can be attributed to a van der Waals interaction. The analysis provides no evidence for long-range electrostatic forces or capillary-induced adhesion of the AFM tip to the fibers studied.

Synthesis, characterization, and antifungal properties of chrome-doped hydroxyapatite thin films

The development of thin films of chromium-doped hydroxyapatite (20CrHAp) deposited on silicon substrate by the spin coating method was realized for the first time. A coherent investigation of the physicochemical properties of 20CrHAp thin films was also carried out for the first time. The obtained thin films were studied by various techniques such as, scanning electron microscopy (SEM), atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR) investigations and fractal analysis. By scanning electron microscopy (SEM) studies were obtained valuable information about the surface morphology of the 20CrHAp thin films. The zeta potential (ZP), Dynamic light scattering (DLS) and ultrasound measurements (US) were used in order to evaluate the stability of 20CrHAp suspension. The ratio between the hydrodynamic diameter obtained by DLS and the particle diameter obtained by SEM was 1.6. The SEM results on 20CrHAp thin films suggested that the sample possess a conglomerate of nanoparticles unevenly distributed on their surface. The surface morphology of the 20CrHAp thin films was studied with the aid of atomic force microscopy (AFM). The AFM topography of the 20CrHAp thin film's surface highlighted that the thin films present the morphology of a continuum deposited layer composed of non-uniform particle conglomerates. The presence of hydroxyapatite on the surface of silicium substrate was revealed by the results of Fourier transform infrared spectroscopy (FTIR) investigations. The antifungal evaluation of the 20CrHAp thin films was performed using Candida albicans 10,231 ATCC fungal strain. The antifungal assays results depicted that the 20CrHAp thin films inhibited the fungal biofilm formation. More than that, the results of the antifungal studies revealed that 20CrHAp thin films exhibited good inhibitory effects on the development of the fungal cells on their surface. Furthermore, our investigation delves into the realm of Minkowski Functionals and fractal/multifractal analysis as applied to the examined films. Our findings reveal that nanocomposite coatings containing 20CrHAp exhibit robust antifungal characteristics, suggesting their viability as a compelling solution for advancing antifungal devices in biomedical contexts.

Innovative surface passivation of CZTSSe thin films: Ammonium sulfide treatment with plasma etching

For CZTS(e) solar cells, the passivation of interfacial defects is crucial for effectively reducing carrier recombination at the interface. This study examined the combined impact of plasma etching and surface sulfuration on the passivation of interface defects in CZTSSe thin films. The results indicated that plasma etching could improve the surface quality of the thin films and passivate surface defects. The (NH4)2S vapor had a significant sulfuration effect on the surface of the CZTSSe thin films post-etching. The surface defects of the CZTSSe film were passivated by the sulfur element entering the film by sulfuration. Moreover, the bandgap of the CZTSSe thin films was improved. The efficiency of the solar cell device increased by 1.72 % with a plasma etching duration of 5 min and (NH4)2S vaporization treatment of 15 min. This study proposes a novel approach that employs surface passivation techniques to enhance the efficiency of CZTSSe thin film solar cells.

Jetsimpy: A Highly Efficient Hydrodynamic Code for Gamma-Ray Burst Afterglow

Gamma-ray burst (GRB) afterglows are emissions from ultrarelativistic blast waves produced by a narrow jet interacting with surrounding matter. Since the first multimessenger observation of a neutron star merger, hydrodynamic modeling of GRB afterglows for structured jets with smoothly varying angular energy distributions has gained increased interest. While the evolution of a jet is well described by self-similar solutions in both ultrarelativistic and Newtonian limits, modeling the transitional phase remains challenging. This is due to the nonlinear spreading of a narrow jet to a spherical configuration and the breakdown of self-similar solutions. Analytical models are limited in capturing these nonlinear effects, while relativistic hydrodynamic simulations are computationally expensive, which restricts the exploration of various initial conditions. In this work, we introduce a reduced hydrodynamic model that approximates the blast wave as an infinitely thin two-dimensional surface. Further assuming axial symmetry, this model simplifies the simulation to one dimension and drastically reduces the computational costs. We have compared our modeling to relativistic hydrodynamic simulations and semianalytic methods, and applied it to fit the light curve and flux centroid motion of GRB 170817A. These comparisons demonstrate good agreement and validate our approach. We have developed this method into a numerical tool, jetsimpy, which models the synchrotron GRB afterglow emission from a blast wave with arbitrary angular energy and Lorentz factor distribution. Although the code is built with GRB afterglow in mind, it applies to any relativistic jet. This tool is particularly useful in Markov Chain Monte Carlo studies and is provided to the community.

Fusion and Positivity in Chiral Conformal Field Theory

In this article we show that the conformal nets corresponding to WZW models are rational, resolving a long-standing open problem. Specifically, we show that the Jones-Wassermann subfactors associated with these models have finite index. This result was first conjectured in the early 90s but had previously only been proven in special cases, beginning with Wassermann’s landmark results in type A. The proof relies on a new framework for the systematic comparison of tensor products (a.k.a. ‘fusion’) of conformal net representations with the corresponding tensor product of vertex operator algebra modules. This framework is based on the geometric technique of ‘bounded localized vertex operators,’ which realizes algebras of observables via insertion operators localized in partially thin Riemann surfaces. We obtain a general method for showing that Jones-Wassermann subfactors have finite index, and apply it to additional families of important examples beyond WZW models. We also consider applications to a class of positivity phenomena for VOAs, and use this to outline a program for identifying unitary tensor product theories of VOAs and conformal nets even for badly-behaved models.

Investigation on the impact of film thickness on spray-deposited Co2SnO4 thin films gas sensing performance towards dimethylamine detection at room temperature

Ternary two-dimensional metal oxide spinel's (A2BO4) have fascinated many researchers due to its inimitable properties such as large reactive surface area, unique phase structure, electrical conductivity, and morphology of the thin film surface. Limitations of a single metal oxide chemi-resistive gas sensor are its higher operating temperature, low detection limit, and long-term stability. In this investigation, a widely employed spray pyrolysis technique is used to deposit different thicknesses of Co2SnO4 thin films. As deposited and annealed films were subjected to all the necessary characterization such as structural, optical, topographical, morphological, and gas sensing performance to understand their performance in real-time application. The synergetic effects of high surface roughness, aggregated porous nanograin morphology, and various physio-chemical properties possibly prompt higher thickness film (A - Co2SnO4) to attain ultrahigh sensor response S = 6074 ± 43, and a good response/recovery time 155 ± 6 s and 44 ± 5 s at 3 ppm at 300 K, respectively. The thin film sensor has excellent long-term stability, repeatability, good moisture resistance, and the lowest detection limit (LOD) with a range of approximately 1 ppm and demonstrates discernible sensor response S = 690 ± 40. These results are the new pathway for tracing dimethylamine gas at room temperature. It can be easily used in food inspection sectors to monitor and detect food freshness.

Reflective Surface for Linear-to-Linear and Linear-to-Circular Polarization Conversion at Multiple Frequencies

In this paper, a thin multiband reflective polarization converter surface is proposed that can reflect a circularly polarized (CP) wave in the following frequency bands: 7.8-8.10 GHz, 8.32-10.04 GHz, 10.80-13.75 GHz, 14.19-14.53 GHz, 16.22-16.52 GHz, and 16.77-17.18 GHz. It can also convert a linearly polarized (LP) incident electromagnetic wave into its orthogonal LP reflection wave in these bands: 8.14-8.25 GHz, 10.23-10.60 GHz, 13.90-14.08 GHz, and 16.59-16.71 GHz. With slotted semicircles supported by a metallic ground plane, the suggested unit cell of the periodic structure has significant stability in all frequency ranges, even at oblique incidence within a 75° angle limit. Furthermore, the suggested polarizer has an easy-to-manufacture construction that only needs one substrate layer and does not include any via holes. A sample prototype consisting of 30×30 unit cells was fabricated and tested, validating our design and simulations.

Time domain reflectometry coil probes for measuring thin surface layer soil moisture: Field tests over 21 years (2002–2022) under highly variable climate conditions in Mongolia

A coil probe (CP) for time-domain reflectometry (TDR) with a sensor length of 40 mm (CP40) was developed for long-term field soil moisture measurements in a thin surface soil layer (0–3 cm depth). In laboratory, soil moisture measurements of CP40 were nearly identical to those of a traditional two-rod type TDR (2RTDR) probe (rod length: 15 cm, diameter: 0.3 cm, spacing: 3 cm). The CP40 measurement accuracy was between 0.01 m3/m3 and 0.03 m3/m3. For long-term field soil moisture measurements, five CP40 units were installed in the highly wetted soil at the Sanzai site (SS), which is in the permafrost area of the Taiga, and dry soil at the Mandalgobi site (MGS) in the semi-arid area of Mongolia. Four units accurately measured soil moisture at both sites over six years (2002–2007and 2008–2009). Three units succeeded in conducting precisely continuous soil moisture measurements between 2008 and 2022 at the MGS. Two units successfully measured soil moisture over 21 years at both the sites. The representativeness of the CP40 soil moisture measurements in highly wetted soils was low because of heavy rainfall and soil heterogeneity. The accuracy of CP40 soil moisture measurements in highly wetted soils was slightly lower than that of the traditional 2RTDR probe. However, the accuracy of the CP40 soil-moisture measurements in the dry soil was comparable to that of the traditional 2RTDR probe. CP40 units are durable and their field soil moisture measurements demonstrate stable and precise performance (bias, RMSE), even under severe environmental conditions.

Defects induced SnOx-TiO2 nanocomposite thin films for improved visible light driven photocatalysis and photoelectrochemical applications

Advanced oxidative removal of organic pollutants from water bodies using nanoparticles of metal oxide photocatalysts is a concurrent hot topic. In the present study, SnOx-TiO2 heterogeneous nanocomposite thin film photocatalysts have been synthesized using SnO and TiO2 precursors by binder-free doctor blade technique. X-ray diffraction was used to confirm the presence of anatase TiO2 as a major phase at elevated temperatures. Raman spectra analysis confirmed phase transformation and defect induction. X-ray photoelectron spectroscopy was utilized to determine the purity and chemical condition of the synthesized thin films. The porous nature of the thin film surface was observed using field emission scanning electron microscopy. UV–Vis-NIR spectroscopy results showed a reduction of bandgap from 3 eV to 2.6 eV with enhanced light absorption. The superior oxygen evolution reaction, redox nature and charge carrier generation were demonstrated using photo-electrochemical techniques. Improved photoresponse of the photocatalysts was observed using chrono-amperometry technique. The superior visible light-driven photocatalytic activity of the samples was demonstrated utilizing cationic and anionic model pollutant dyes. The reusability of the catalyst is ensured through successive photodecomposition processes. These results show a facile fabrication of defects induced heterogenous nanocomposite photocatalyst thin films with improved visible light activity.

Exploring the structural, photophysical, and electrical properties of Dopant-Free hole transporting material based on 2, 7-carbazole from experimental to simulation

This paper presents the development of a dopant-free HTM as a thin film, utilizing carbazole (2,7) as a central building block. The deposition of homogeneous thin films of HTM2 was successfully achieved through Physical Vapor Deposition. The morphological, optical, and electrical properties of the fabricated samples were extensively studied using techniques such as Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM), UV–visible spectroscopy, and Photoluminescence Technique. The AFM and SEM analyses demonstrated the uniformity and flatness of the thin film surfaces. The UV spectra results indicated that the maximum absorption spectra did not exhibit significant shifts when measured in chlorobenzene solvent, with an estimated band gap of approximately 2.96 eV. Photoluminescence spectroscopy and decay time measurements were conducted on HTM2 thin films, which revealed emission in the green-yellow region. The photoluminescence spectra of the thin films exhibited red-shifted emission bands compared to the solution, attributable to stronger π-π intermolecular interactions resulting in the closeness of the molecules in the solid state. This work finally couples the theoretical and experimental results to validate our obtained results and to get an idea about the efficiency of the cell-based HTM2. The obtained results confirmed that the investigated material can find applications in perovskite solar cells.