Laser-induced Defects Research Articles

Laser-induced stripping defect for highly selective electrochemical quantification of dopamine: Anti-interference from other catecholamine neurotransmitters

Detecting dopamine (DA) is critical for early diagnosis of neurological and psychiatric disorders. However, the presence of other catecholamine neurotransmitters with structural similarities to DA causes significant interference in its detection. Herein, we introduce S stripping defects via laser-induced MoS2 to functionalize MoS2 electrodes and improve their selectivity for DA electrochemical detection. The sensing results show its excellent immunity to interference from other neurotransmitters, ensuring the preservation of the DA electrochemical signal even in the mixed neurotransmitters such as acetylcholine (ACh), γ-aminobutyric acid (GABA), epinephrine (EP), norepinephrine (NP), and serotonin (5-HT). DFT calculations further reveal that the negatively charged S-stripping defects enhance DA adsorption on the surface of the functionalized MoS2 electrode, contributing to its excellent performance. Moreover, this functionalized electrodes successfully monitor DA released from living PC12 cells in the presence of other interference, highlighting its potential applicability in intercellular signaling communication.

Reducing the Metal-Graphene Contact Resistance through Laser-Induced Defects.

Graphene has been extensively studied for a variety of electronic and optoelectronic applications. The reported contact resistance between metal and graphene, or rather its specific contact resistance (R C), ranges from a few tens of Ω μm up to a few kΩ μm. Manufacturable solutions for defining ohmic contacts to graphene remain a subject of research. Here, we report a scalable method based on laser irradiation of graphene to reduce the R C in nickel-contacted devices. A laser with a wavelength of l = 532 nm is used to induce defects at the contact regions, which are monitored in situ using micro-Raman spectroscopy. Physical damage is observed using ex situ atomic force and scanning electron microscopy. The transfer length method (TLM) is used to extract R C from back-gated graphene devices with and without laser treatment under ambient and vacuum conditions. A significant reduction in R C is observed in devices where the contacts are laser irradiated, which scales with the laser power. The lowest R C of about 250 Ω μm is obtained for the devices irradiated with a laser power of 20 mW, compared to 900 Ω μm for the untreated devices. The reduction is attributed to an increase in defect density, which leads to the formation of crystallite edges and in-plane dangling bonds that enhance the injection of charge carriers from the metal into the graphene. Our work suggests laser irradiation as a scalable technology for R C reduction in graphene and potentially other two-dimensional materials.

A Novel 3D High Resolution Imaging Method Using Correlative X-Ray and Electron Microscopy to Study Neodymium-Doped Yttrium Aluminum Garnet Laser-Induced Defects in Intraocular Lenses.

Cataract extraction is the most frequently performed ophthalmological procedure worldwide. Posterior capsule opacification remains the most common consequence after cataract surgery and can lead to deterioration of the visual performance with cloudy, blurred vision and halo, glare effects. Neodymium-doped yttrium aluminum garnet (Nd:YAG) laser capsulotomy is the gold standard treatment and a very effective, safe and fast procedure in removing the cloudy posterior capsule. Damaging the intraocular lens (IOL) during the treatment may occur due to wrong focus of the laser beam. These YAG-pits may lead to a permanent impairment of the visual quality. In an experimental study, we intentionally induced YAG pits in hydrophilic and hydrophobic acrylic IOLs using a photodisruption laser with 2.6 mJ. This experimental study established a novel 3D imaging method using correlative X-ray and scanning electron microscopy (SEM) to characterize these damages. By integrating the information obtained from both X-ray microscopy and SEM, a comprehensive picture of the materials structure and performance could be established. It could be revealed that although the exact same energies were used to all samples, the observed defects in the tested lenses showed severe differences in shape and depth. While YAG pits in hydrophilic samples range from 100 to 180 µm depth with a round shape tip, very sharp tipped defects up to 250 µm in depth were found in hydrophobic samples. In all samples, particles/fragments of the IOL material were found on the surface that were blasted out as a result of the laser shelling. Defects in hydrophilic and hydrophobic acrylic materials differ. Material particles can detach from the IOL and were found on the surface of the samples. The results of the laboratory study illustrate the importance of a precise and careful approach to Nd:YAG capsulotomy in order to avoid permanent damage to the IOL. The use of an appropriate contact glass and posterior offset setting to increase safety should be carried out routinely.

Controlling ultrafast laser writing in silica glass by pulse temporal contrast.

We demonstrate that the temporal contrast of femtosecond light pulses is a critical parameter in laser writing inside transparent dielectrics, allowing different material modifications. In particular, anisotropic nanopores in silica glass are produced by high-contrast of 107 femtosecond Yb:KGW laser pulses rather than low-contrast of 103 Yb fiber laser pulses. The difference originates in the fiber laser storing a third of its energy in a post-pulse of up to 200 ps duration. The absorption of this low-intensity fraction of the pulse by laser-induced transient defects with relatively long lifetime and low excitation energy, such as self-trapped holes, drastically changes the kinetics of energy deposition and the type of material modification. We also demonstrate that low-contrast pulses are effective in creating lamellar birefringent structures, possibly driven by a quadrupole nonlinear current.

Analysis of laser-induced surface damage of single-crystal Ni-based superalloy towards improving machinability

Single-crystal (SC) nickel-based superalloys provide improved high-temperature strength, and resistance to creep, fatigue and oxidation, compared to equiaxed and columnar-grained components due to their higher solid solution strengthening, precipitation hardening and the absence of grain boundaries. However, the SC nickel-based superalloys are ‘difficult-to-cut’. To enhance the machinability, a concept of laser-induced surface damage (LISD)-assisted machining is being studied. Laser surface modification (LSM) experiments were been performed by employing the design of experiments (DoE) strategy L18, OA (orthogonal array). The LSMed geometries were characterized to identify various laser-induced surface defects including solidification cracks, microcracks, micropores, microstructural changes, phase changes, recrystallization, and deformation. Further, parametric interactions and optimization of the process parameters were performed to manufacture a larger LISD layer. The parameter-structure-property relationship was derived systematically and the mechanisms of LISD on the SC nickel-based superalloy were described in details. The results indicate that the LISD increase with an increase in laser power followed by a decrease in scan speed and beam diameter. LISD geometries possess 1 % to 4 % of crack density and lower hardness of around 27 % than the base metal. Slot milling experiments were then conducted on the LISD specimens, which showed up to a 40 % reduction in cutting forces when compared to untreated specimens. It is evident that this methodology can be adopted to further improve the machinability of various difficult-to-cut materials.

Engineering intrinsic defects in CuO NWs through laser irradiation: Oxygen vs copper vacancies

Defect engineering in CuO nanomaterials has been extensively investigated because this technology can greatly improve the performance of CuO components in a variety of applications. While many previous studies have focused on the role of oxygen vacancies, (VO), in CuO, little attention has been paid to that of copper vacancy centers, (VCu), since the presence of these defects is often difficult to quantify. As a result, the specific roles played by these different vacancy centers on the measured properties of CuO have not been studied systematically. In this article, we show that the concentration of both VO and VCu centers can be engineered in CuO NWs through nanosecond (ns) laser irradiation. The identification of these vacancies was achieved through X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. Absorption spectra and diffuse reflectance spectra of laser-processed samples show that increasing the concentration of VO centers enhances the optical absorption of CuO in the visible region. Data obtained from Mott-Schottky and Nyquist plots, together with measured I-V characteristics, show that laser-induced VCu centers can enhance the carrier concentration in CuO NWs. These data, in addition to O 1s XPS spectra on laser-processed and unprocessed samples as well as cyclic voltammetry, also indicate that laser irradiation can significantly enhance surface adsorption for applications in photo-electrochemistry and electrochemistry. To demonstrate the efficacy of this laser irradiation technique for potential electrochemistry applications, the role of laser-induced VCu and VO defect centers in CuO NWs on the non-enzymatic sensing of glucose has also been investigated. We find that the introduction of VO centers in CuO NWs enhances the current response for glucose sensing while the presence of VCu centers inhibits this response.

Laser-induced oxygen vacancy defect Mn7O13·5H2O as binder-free cathode for high performance all-in-one zinc-ion battery

Reachable Zinc ion batteries (ZIBs) are regarded as promising large scale energy storge systems because of their advantages of high safety, high energy density (high volumetric capacity), and economic benefits. However, ZIBs suffer from of lack of suitable cathode materials with high capacity and long stability of circulation. In addition, conventional coating process to prepare cathode with binder (PVDF/PTFE et al.) will not only reduce active material loading but also hinder ion transmission. Hence, a simple binder-free cathode prepare process was proposed. We use laser irradiation the Mn7O13·5H2O/graphene oxide cathode. The laser irradiation will induce vacancy defect in the Mn7O13·5H2O, leading to more active contact sites. Finally, the prepared materials achieve an ultra-high specific capacity of 411.6 mAh g−1 (0.2 A g−1), an excellent rate performance (176.3 mAh g−1 at a current density of 5 A g−1), and a satisfactory capacity retention rate of 90.1% after long 3500 cycles at 2 A g−1. The assembled all-in-one architecture battery has a fair specific capacity of 177.3 mAh g−1 at the current density of 2 A g−1. This work opens up a new horizon for conveniently preparing binder-free cathode materials with defects for high energy density and long cycle life.

Direct Laser Irradiation and Modification of 2D Te for Development of Volatile Memristor.

Laser irradiation, as a kind of post-fabrication method for two-dimensional (2D) materials, is a promising way to tune the properties of materials and the performance of corresponding nano-devices. As the memristor has been regarded as an excellent candidate for in-memory devices in next-generation computing system, the application of laser irradiation in developing excellent memristor based on 2D materials should be explored deeply. Here, tellurene (Te) flakes are exposed to a 532 nm laser in the air atmosphere to investigate the evolutions of the surface morphology and atom structures under different irradiation parameters. Laser is capable of thinning the flakes, inducing amorphous structures, oxides and defects, and forming nanostructures by controlling the irradiation power and time. Furthermore, the laser-induced oxides and defects promote the migration of metal ions in Te, resulting in the formation of the conductive filaments, which provides the switching behavers of volatile memristor, opening a route to the development of next-generation nano-devices.

Pulsed laser-assisted synthesis of nano nickel(ii) oxide-anchored graphitic carbon nitride: Characterizations and their potential antibacterial/anti-biofilm applications

Abstract Nickel(ii) oxide-graphitic carbon nitride (n-NiO@g-C3N4) nanocomposite, in which nickel oxide nanoparticles (n-NiO) are anchored on the polymeric surface of graphitic carbon nitride (g-C3N4), was synthesized using the pulsed laser post processing (PLPP) in liquid medium. In the PLPP method, the precursors (NiO and g-C3N4) were simultaneously subjected to pulsed laser-induced fragmentation, and pulsed laser-induced defect engineering (anchoring of NiO on g-C3N4). To optimize the functionality of the material, n-NiO@g-C3N4 with four different mass contents of n-NiO was synthesized. The synthesized n-NiO@g-C3N4 nanocomposite and its composite partners (n-NiO and g-C3N4) were structurally, morphologically, elementally characterized by X-ray diffraction, filed emission scanning electron microscope, transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) analyses. As a first anti-microbial application, n-NiO@g-C3N4 was used to evaluate the minimal inhibitory concentration and minimal bactericidal concentration against the gram-positive Staphylococcus aureus and gram-negative Pseudomonas aeruginosa bacteria. As a second anti-microbial application, the efficacy of n-NiO@g-C3N4 nanocomposite to retard S. aureus and P. aeruginosa biofilms’ growth was evaluated. It was found that for both applications, n-NiO@g-C3N4 nanocomposite exhibited an excellent anti-bacterial activity compared to pure g-C3N4.

Few-cycle optical field breakdown and damage of gallium oxide and gallium nitride

Both gallium oxide and gallium nitride have great potential for use as high power transparent conducting oxide materials for a wide range of optoelectronic applications. It is, therefore, important to determine the dynamic optical field breakdown for these materials. Here, we report laser damage thresholds for Ga2O3 and GaN using 9 fs few-cycle pulses with a center wavelength near 760 nm. We determine laser-induced damage thresholds (LIDTs) for both single pulse and multi-pulse exposures, with multi-pulse LIDT showing significant reduction compared to single pulse LIDT (in some cases, >50%), possibly due to laser-induced defects. We show that Ga2O3 and GaN have an ultrafast optical field breakdown of 23 and 18 GV/m when nearly polarized along their [010] and [111] planes, respectively, extending their suitability for high power applications to the ultrashort pulse regime. To accurately characterize the excited carrier density criteria in which apparent laser damage occurs, carrier excitation dynamics for the entire laser pulse interaction were simulated using a modified Keldysh ionization model. For the measured single-shot threshold fluences, the plasma critical density was surpassed by 2 orders of magnitude and 2D finite-difference time-domain simulations were employed to understand the pulse interaction near the surface.

Determination of intrinsic defects of functional KDP crystals with flawed surfaces and their effect on the optical properties

A practically nonlinear optical material, the functional KH2PO4 (KDP) crystal, has an extremely low laser-induced damage threshold (LIDT) due to manufacturing-induced surface defects. The low LIDT induced by these surface defects of KDP crystals hinders their application in laser fusion facilities. Herein, the effect of intrinsic point defects introduced by manufacturing-induced lateral cracks on laser damage was particularly investigated by a combination of spectral detection (i.e., photoluminescence, Raman and Fourier transformed infrared spectra) and first-principles calculation. It was determined that the manufacturing-induced lateral cracks would introduce more hydrogen vacancy and oxygen vacancy intrinsic defects than the ideal surface. These intrinsic defects would form cluster-type defects, lowering the LIDT to 6.600 J cm-2 by introducing two defect levels of 2.83 eV and 4.89 eV within the band gap of the KDP crystal. To further investigate the effect of intrinsic defects introduced by lateral cracks on laser-induced damage growth, the transformation of charge states of intrinsic defects under laser irradiation was calculated. Combined with the spectral information of the lateral crack-induced laser damage site and the laser damage growth experiments, it was found that the intrinsic defects of lateral cracks have a large amount of evolution, making the crystal prone to severe damage growth. Overall, the avoidance of such lateral cracks with a large number of intrinsic defects is very beneficial for improving the laser damage resistance of KDP crystals.

Improved Laser-Induced Defect Passivation and Simultaneous Elimination of Light-Induced Degradation in p-Type Czochralski Silicon

Laser doping is a typical industrial method to introduce a local highly doped region in silicon solar cells to form a selective emitter. Such a process inherently introduces defects that can be a concern to the overall performance of the solar cell. Here, we investigate the effectiveness of laser-induced defect (LasID) passivation on lifetime test structures through different annealing processes, including high-temperature belt-furnace firing, low-temperature belt-furnace annealing, and an advanced hydrogenation process (AHP) for n+ laser-doped selective emitters. We demonstrate clear advantages of post treatment using a rapid 10 s AHP at 300 °C when the lifetime structures are prefired. For the examined laser speeds of 0.5–6 m/s (sheet resistances of 4--70 Ω/□), AHP is the most effective treatment method. For example, for a typical laser doping speed of 4 m/s, starting from the same effective carrier lifetime of 36.9±2.4 μs after laser-doping step for all the passivation treatments, the AHP not only surpasses the conventional approaches by showing the highest recovery of the effective carrier lifetime (∼79% compared with ∼63% and ∼41% for the firing and belt-furnace annealing treatments, respectively) and dark saturation current density reduction in the regions affected by LasIDs but also simultaneously suppresses light-induced degradation (maximum of 4% effective lifetime degradation with respect to the passivated state, as opposed to 14% and 16% degradation for the firing and belt-furnace annealing treatments, respectively) common in Cz grown boron-doped p-type monocrystalline silicon.

Few pulses femtosecond laser exposure for high efficiency 3D glass micromachining.

Advanced three-dimensional manufacturing techniques are triggering new paradigms in the way we design and produce sophisticated parts on demand. Yet, to fully unravel its potential, a few limitations have to be overcome, one of them being the realization of high-aspect-ratio structures of arbitrary shapes at sufficiently high resolution and scalability. Among the most promising advanced manufacturing methods that emerged recently is the use of optical non-linear absorption effects, and in particular, its implementation in 3D printing of glass based on femtosecond laser exposure combined with chemical etching. Here, we optimize both laser and chemical processes to achieve unprecedented aspect ratio levels. We further show how the formation of pre-cursor laser-induced defects in the glass matrix plays a key role in etching selectivity. In particular, we demonstrate that there is an optimal energy dose, an order of magnitude smaller than the currently used ones, yielding to higher process efficiency and lower processing time. This research, in addition to a conspicuous technological advancement, unravels key mechanisms in laser-matter interactions essential in chemically-based glass manufacturing and offers an environmentally-friendly pathway through the use of less-dangerous etchants, replacing the commonly used hydrofluoric acid.

Effect of 532 nm Nd:YAG laser irradiation on the optical properties of Ge1Se2.5 glass film

Ge1Se2 .5 alloy was prepared using the melt quenching method and the film was deposited by the thermal evaporation method. The as-prepared film was irradiated with Nd:YAG laser at 532 nm wavelength for different durations. The structural and morphological characterization indicates that the film has nanoparticles of different shapes with sizes varying from 80 to 300 nm and the structure becomes more crystalline on laser irradiation. The refractive index of the film increases, while the band gap decreases on laser irradiation. The dispersion behaviour of refractive index was studied using the WDD model. The decrease in band gap is attributed to the increase of laser-induced defects, which consequently narrows the energy gap. The non-linear optical parameters were found to increase with an increase in laser irradiation time. The increase in these parameters and transformation from the amorphous to the polycrystalline phase make laser-irradiated films suitable for non-linear optical devices and optical recording media.

Microscale patterning of semiconductor c-Si by selective laser-heating induced KOH etching

Laser patterning has been used for the micro-scale fabrication of semiconductor devices like solar cells, photodetectors, LEDs, and also for modification of surfaces for wettability, reflected colors, initial bacterial adhesion, etc, due to its several advantages of patterning flexibility, spatial resolution, and mask-free operation over complex conventional lithography. Currently, laser-induced ablation is a promising patterning method in silicon solar cell fabrication; however, laser-induced defects, and thermal stresses remain a significant concern. In this paper, we demonstrate a laser ablation-free method for patterning c-Si based on the observation that the anisotropic etching of c-Si by KOH is highly temperature-dependent as the etching rate is about 100 times faster at 80 °C compared to room temperature. The laser heating-induced chemical etching (LHICE) of crystalline silicon can help alleviate such laser-induced damage by providing the necessary low temperature on the localized area(s) on the silicon substrate. We investigated the micro-second pulsed laser-assisted chemical etching of c-Si substrate for microscale patterning and showed that laser-induced damage could be eliminated as indicated by the minority carrier lifetime preservation. We also present results of the effect of laser processing parameters such as laser power, scan speed, and duty cycle on etching depth and surface morphology. The optical, surface morphology, depth profile, and LCPSim simulation results are also presented to optimize and understand the LHICE process. This versatile methodology of temperature-selective chemical etching could be applied to various thin-film and bulk materials used in diverse device fabrication.

Femtosecond laser polishing of SiC/SiC composites: Effect of incident angle on surface topography and oxidation

In this article, a new ultrafast laser polishing method for SiC/SiC composites was reported and the effects of different incident angles were discussed in detail. The results indicated that the incident angle had a great influence on the polishing of SiC/SiC composites. Under the normal incident condition, the surface roughness was barely improved and the laser-induced defects even degraded the process quality. With the increasing incident angle, surface oxidation and defects dramatically decreased. At 80 degrees, the surface convex structure is almost eliminated and the protruding fiber was neatly cut off. Furthermore, a theoretical model of laser polishing for SiC/SiC composites is used to analyze the laser propagation and power density distribution in different incident angles. The model successfully predicted the laser energy resonance enhancement and illustrated the formation mechanism of laser-induced defects and nanoripples. Meanwhile, the result shows that the laser energy concentrated on the convex fiber of composites as the incident angle increased, which explained that the SiC/SiC composites polishing quality was significantly improved under the inclined incident condition.

Nanosecond Pulsed Laser Patterning of Interdigitated Back Contact Heterojunction Silicon Solar Cells

Careful control of the laser patterning for the fabrication of an interdigitated back contact heterojunction (IBC-HJ) solar cell is needed to avoid laser-induced defects and heat-induced crystallization, which can produce higher carrier recombination and lower power conversion efficiency. The results of nanosecond laser patterning of an IBC-HJ test structure are reported, and it was shown that optimized laser ablation conditions using a sacrificial layer eliminates laser-induced damage of the underlying passivation layer. A rigorous set of characterizations, comprising of minority carrier lifetime, spatially resolved μ-photoluminescence, optical microscopy, ellipsometry, Essential Macleod program simulations, scanning electron microscopy, line-mapping energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy, were undertaken to provide a deeper understanding of the nanosecond laser processing under a wide range of laser fluence. The evolving changes in surface morphologies of top sacrificial a-Si and SiNx and the use of color chart simulation for ablation-depth analysis were investigated. The μ-photoluminescence, carrier lifetime, and crystallinity in the passivation layer were evaluated. The trend in the change in the surface chemical constituency was determined in terms of Si/N ratio. Finally, the minimum laser fluence for the IBC-HJ test structure was determined and a negligible change in the implied open-circuit voltage was demonstrated.

Laser-induced reactive microplasma for etching of fused silica

The ultra-precise machining (UPM) of surfaces with contact-free, beam-based technologies enables the development of flexible and reliable fabrication methods by non-vacuum processes for future application in advanced industrial fields. Laser machining by laser ablation features limitations for ultra-precise machining due to the depth precision, the surface morphology, and laser-induced defect formation. Contrary to physically-based etching, chemical-based dry and wet processing offer high quality, low damage material removal. In order to take advantage of both principles, a combined laser-plasma process is introduced. Ultra-short laser pulses are used to induce a free-standing microplasma in a CF4 gas atmosphere due to an optical breakdown. CF4 gas, with a pressure of 800–900 mbar, is ionized only near the focal point and reactive species are generated therein. Reactive species of the laser-induced microplasma can interact with the surface atoms of the target material forming volatile products. The release of these products is enhanced by the pulsed, laser-induced plasma resulting in material etching. In the present study, SiO2 surfaces were etched with reactive species of CF4 microplasma generated by their laser-induced break down with 775 nm pulses of an fs-laser (150 fs) at a repetition rate of 1 kHz. The dependency of the depth, the width, and the morphology of the etching pits were analysed systematically against the process parameters used. In particular, a linear increase of the etching depth up to 10 µm was achieved. The etched surface appears smooth without visible cracks, defects, or LIPSS (Laser-induced periodic surface structures).

Laser-processing of grinded and mechanically abraded Nb-surfaces

The effect of pulsed laser polishing on rough niobium surfaces was investigated. We created different well-defined roughness profiles with standard emery papers and subsequently remelted random surface areas with a size of about 2 × 2 mm2 with nanosecond laser pulses (wavelength of 1064 nm, pulse length of 10 ns). Pristine as well as laser-treated surfaces were investigated using optical profilometry and atomic force microscopy, and the surface topography was described by means of correlation functions. Uniformly rough and highly smooth surface geometries were achieved for fractals above and below 7 μm, respectively. Moreover, the behavior of foreign particles during the laser processing was investigated in detail. The polishing procedure was also monitored point by point by detecting electrical signals, i.e., sample charging, which resulted from the intense laser illumination. The measured electrical charges were found to be correlated with the local surface texture. Thus, regions with initially high roughness profiles and regions with extensive laser-induced defects could be directly identified from the detected electrical signals.

Self-aligned local contact opening and n+ diffusion by single-step laser doping from POx/Al2O3 passivation stacks

Laser doping is a promising route to realise industrially compatible processing of local contacts for high-efficiency solar cells, especially when the same film acts as both dopant source and passivation layer. In this work we demonstrate simultaneous local contact opening and n+ laser doping of silicon from positively charged POx/Al2O3 thin-film stacks, which also provide outstanding passivation of n-type silicon surfaces. Local n+ doped regions with sheet resistance ranging from 35 to ~540 Ω/□ are formed using single nanosecond laser pulses with varying fluence. ECV profiling shows net n-type doping in all cases, confirmed by SIMS profiling to be due to phosphorus from the POx layer. J0 of metallised laser-doped regions is consistent with values achieved for state-of-the-art furnace diffusions with similar sheet resistance, confirming that laser-induced recombination-active defects are avoided. A minimum J0 of 540 fA cm−2 is obtained for metallised laser-doped regions formed from POx/Al2O3 passivation stacks having J0 of 2.5 fA cm−2. The combination of outstanding passivation of uncontacted n-type regions offered by POx/Al2O3, with self-aligned formation of locally-diffused contact openings via single-step laser processing, opens up exciting possibilities for simplified fabrication of high-efficiency cell structures.