Laser Scribing Process Research Articles

A novel laser scribing method combined with the thermal stress cleaving for the crystalline silicon solar cell separation in mass production

Nowadays as the wafer sizes of the crystalline silicon solar cells get larger and larger, separating the cells becomes an essential step. However, in mass production, there is still lack of a low scribing loss and broad compatible cell separation method. In this work, a systematic investigation was conducted on the crystalline silicon solar cell separation processes, including the laser scribing and the cleaving process. Firstly, by combining a 1/4 beam splitter with the laser head, we developed a new laser scribing process, which can achieve a smaller groove width-to-depth ratio (24%) with narrower heat affected area (total width of 30 μm) compared to traditional laser optical systems. Then, we explored the minimum required scribing depths for separating four typical crystalline silicon cells by applying the thermal stress cleaving process. The Czochralski-grown substrates need only point scribing at the beginning and the end of the separating path, but if there is a metal electrode in the separation path, the scribing depth has to be about 20% of the cell thickness. At last, we analyzed the electrical and mechanical strength losses caused by different separation processes. The 20% scribing depth may cause about 30%rel mechanical strength loss. It is proved that combining this new scribing method with the thermal stress cleaving is an economical separation solution with less laser scribing loss and better compatibility for different cells. Our results would shed some light on future separating and module design efforts of solar cells.

Research Status and Prospect of Laser Scribing Process and Equipment for Chemical Milling Parts in Aviation and Aerospace.

Laser scribing in chemical milling is an important process which can effectively improve the precision and efficiency of chemical milling, and is of great significance to improve the thrust–weight ratio and manufacturing efficiency of aviation and aerospace parts. According to the scribing requirements in chemical milling for aviation and aerospace parts, the process and mechanism of laser scribing were studied and the influence of different process parameters for the quality of laser scribing was analyzed. Based on the review of related research literature, the laser scribing process, the ablation mechanism and technology of different materials and the selective laser removal process for “laser–coating–substrate” are summarized and discussed. Based on the requirements of high-precision laser scribing on complex surfaces, the current situation of laser scribing equipment is summarized. Finally, the practical challenges and key technical problems for the laser scribing process are summarized, and the application and development of laser scribing in aerospace manufacturing are prospected.

Real-Time Monitoring and Defect Detection of Laser Scribing Process of CIGS Solar Panels Utilizing Photodiodes

Laser scribing is developing rapidly in industrial applications as a method of material processing, especially in areas that require high levels of precision. This technology provides functionality and efficiency improvements in the manufacturing of solar panels. Due to the premium quality and speed requirements of the laser scribing technology, monitoring of this process in real-time is critical in order to promptly detect defects in the manufacturing process. However, common monitoring systems have been developed for other laser processes, like laser welding, which are noticeably slower than the laser scribing process. The goal of this research was to investigate the possibility of using photodiodes for real-time monitoring of the laser scribing process for Copper Indium Gallium Selenide (CIGS) solar panels. Various monitoring setup configurations were designed, developed, and examined to determine the viable option for implementation as a defect detection platform. Using different photodiode positions, the intensity of the light and the photodiode induced voltage for diffuse and specular reflections were tested, and the practical pros and cons of applying each configuration were analyzed. The capability of the monitoring system to distinct the different layers of the scribed CIGS cell was also examined to assess the penetration depth of the scribe. In addition, by performing several experiments with different scribe thicknesses and analyzing oscilloscope measurements, the optimal placement of the photodiode for accurate tracing of the scribing path was determined and verified. Key aspects of development of such monitoring system for solar panel applications were identified through this research.

Real-Time Monitoring and Control of Ultra-Fast Laser Engraving Process Utilizing Spectrometer

The objective of this study was to develop a novel real-time monitoring and control method for ultra-fast laser scribing processes utilizing spectrometer. Adjustment of laser process parameters such as laser power with high precision in real-time is critical in the laser engraving process due to the premium quality and speed requirements of the process. An online monitoring system was established using the Ocean Optics spectrometer, IPG ytterbium pulsed laser, and PXIe-8880 industrial computer. An algorithm for real-time control of the laser scribing process was developed based on the monitoring outcomes using LabVIEWⓇ software. Experimental methods were performed to evaluate the reliability of the developed monitoring system and control algorithm. The sensitivity of the spectrometer was assessed by changing laser power, pulse length, and focal point position. A workpiece consisting of two different metals, including stainless steel SS304L and steel S355, was used to evaluate the performance of the developed algorithm when scribing moved from one material to another. Instant accurate setting of the laser power based on the variations in intensities of metals from 750 AU to 1400 AU validated the reliability of the algorithm.

Laser synthesis of superhydrophilic O/S co-doped porous graphene derived from sodium lignosulfonate for enhanced microsupercapacitors

Porous graphene with rational heteroatoms doping has been widely researched as one of the most prominent materials for application in supercapacitors. Herein, we implement a green and facile laser engraving strategy to synthesize three-dimensional (3D) superhydrophilic and oxygen (O)-sulfur (S) co-doped porous graphene electrodes. Specifically, the mixed sodium lignosulfonate slurry is evenly coated on the laser-induced graphene (LIG) interdigital electrodes, and followed by a duplicated laser scribing process. The as-prepared materials can synchronously possess hierarchical porous graphene architectures, superior hydrophilicity, and O/S co-doped chemistry properties, which can significantly promote the penetration and transport of electrolyte ions and provide extra pseudocapacitance. Benefiting from these advantages, satisfactory capacitive performance of the assembled MSCs is obtained, such as an outstanding areal capacitance of 53.2 mF cm−2@0.08 mA cm−2, which is about 39 times larger than of undoped MSC. Moreover, remarkable mechanical flexibility, excellent modular integration capability as well as good cycling stability (81.3% capacitance retention after 8000 cycles) have been also achieved. As such, this study offers a novel and efficient strategy for valuable utilization of biomass lignosulfonate, and the as-prepared heteroatom-doped superhydrophilic porous graphene holds enormous promise for high-performance energy storage devices.

Highly sensitive piezoresistive pressure sensors based on laser-induced graphene with molybdenum disulfide nanoparticles

Wearable pressure sensors have drawn significant attention because of their extensive applications in motion detection, tactile sensing, and health monitoring. However, the complex manufacturing process and high cost of active materials make low-cost, large-scale production elusive. In this work, we report a flexible piezoresistive pressure sensor assembled with two 3D laser-induced graphene (LIG) foam electrodes on a polyimide thin film from a simple laser scribing process in the ambient environment. The design of the air gap between the two foam electrodes allows the sensor to showcase a low limit of detection of 0.274 Pa, which provides favorable sensing performance in motion detection and wrist pulse monitoring. The addition of spherical MoS2 nanoparticles between the two foam electrodes further enhances the sensitivity to 88 kPa−1 and increases the sensing range to significantly outperform the previous literature reports. The demonstrated LIG pressure sensors also exhibit fast response/recovery rates and excellent durability/repeatability.

Enhanced Electrochemical Performance of Micro-Supercapacitors Via Laser-Scribed Cobalt/Reduced Graphene Oxide Hybrids.

The evolution of "smart life," which connects all internet-of-things (IoT) microdevices and microsensors under wireless communication grids, requires microscale energy storage devices with high power and energy density and long-term cyclability to integrate them with sustainable power generators. Instead of Li-ion batteries with a short lifetime, pseudocapacitors with longer or infinite cyclability and high-power density have been considered as efficient energy storage devices for IoT. However, the design and fabrication of microscale pseudocapacitors have difficulties in patterning microscale electrodes when loading active materials at specific points of the electrodes using conventional microfabrication methods. Here, we developed a facile, one-step fabrication method of micro-supercapacitors (MSCs) through the in situ formation of Co metals and the reduced graphene oxides (rGOs) in a one-pot laser scribing process. The prepared Co/rGO MSC thus exhibited four times higher capacitance than the rGO MSC, due to the Faradaic charge capacitance behavior of the Co/rGO composites.

Disposable and portable gold nanoparticles modified - laser-scribed graphene sensing strips for electrochemical, non-enzymatic detection of glucose

Glucose is one of the most important metabolites and a primary nutrient in human body metabolism. Abnormal levels of glucose can cause diabetes mellitus and related complications. Here, we developed a disposable and portable non-enzymatic glucose sensor strip based on gold-nanoparticles (AuNPs)-modified laser-scribed graphene electrode (LSGE). Disposable LSGEs, with a highly porous structure, were fabricated by laser scribing on a commercially available polyimide plastic sheets, followed by electrodepositing of AuNPs, that are electrocatalytic for glucose oxidation. The laser scribing process was optimised in term of laser power, laser speed and pulse per inch (PPI). The effect of number of the electrochemical deposition cycles of AuNPs on LSGE was also investigated and optimised. The sensor provides a linear detection range for the glucose concentrations between 10 µM to 10 mM with a limit of detection of 6.3 µM and shows a good selectivity towards interfering agents, such as urea L-ascorbic acid, uric acid, dopamine, and Na+. The LSGE/AuNP strips have a potential to be used as disposable glucose sensor strips for point-of-care glucose measurements, including self-monitoring and nutrition management.

Flexible Hall sensor made of laser-scribed graphene

Graphene has shown considerable potential for sensing magnetic fields based on the Hall Effect, due to its high carrier mobility, low sheet carrier density, and low-temperature dependence. However, the cost of graphene in comparison to conventional materials has meant that its uptake in electronic manufacturing has been slow. To lower technological barriers and bring more widespread adoption of graphene Hall sensors, we are using a one-step laser scribing process that does not rely on multiple steps, toxic chemicals, and subsequent treatments. Laser-scribed graphene Hall sensors offer a linear response to magnetic fields with a normalized sensitivity of ~1.12 V/AT. They also exhibit a low constant noise voltage floor of ~ 50 nV/sqrt {{mathrm{Hz}}} for a bias current of 100 µA at room temperature, which is comparable with state-of-the-art low-noise Hall sensors. The sensors combine a high bendability, come with high robustness and operating temperatures up to 400 °C. They enable device ideas in various areas, for instance, soft robotics. As an example, we combined a laser-scribed graphene sensor with a deformable elastomer and flexible magnet to realize low-cost, compliant, and customizable tactile sensors.

Characterization of the Laser Scribing Process of HIT Cells for a Photovoltaic Shingled Module

Shingled string technology can be used to maximize the output power of photovoltaic modules. The maximum power (Pmax) of a shingled photovoltaic module can be increased by using a bifacial heterojunction with an intrinsic thin layer (HIT) of cells. To fabricate the shingled strings for a high power module, we first cut 6-inch solar cells by laser scribing while minimizing cutting loss. Unlike standard crystalline silicon (c-Si) solar cells, the structure of bifacial HIT solar cells is weak under thermal effect, so an optimal scribing condition had to be found. After laser scribing processes had been optimized, Pmax was increased by 0.02W for each separated solar cells when we using an ultraviolet (UV) laser compared to the green laser, and a UV cut shingled string of HIT cell was demonstrated for the first time.

Crack propagation evaluation using virtual prototyping techniques

A methodology for crack propagation using virtual prototyping (VP) is demonstrated. It is based on a classical approach to assess crack propagation, improved with finite element analysis tools. It enables to examine in detail all aspects of crack formation and to evaluate the probability of its occurrence. Performed demonstration is based on Al2O3 substrate laser scribing process and its assessment in direction of possible crack occurrence. Presented study gives basic directions on application of virtual prototyping in crack initiation and propagation prediction. This approach gives the opportunity to monitor various parameters as stresses and to predict influence of various design changes over examined physical process output parameters.

Laser-Scribed Graphene Electrodes Derived from Lignin for Biochemical Sensing

Laser scribing of porous graphene electrodes on flexible substrates is of great interest for developing disposable electrochemical biosensors. In this work, we present a new patterning process for highly conductive nitrogen-doped graphene derived from a lignin-based precursor. A CO2 laser scribing process was performed under ambient conditions to produce the porous graphene electrodes from lignin. The obtained nitrogen-doped laser-scribed graphene (N-LSG) is binder-free, hierarchical, and conductive. The interconnected carbon network displayed enhanced electrochemical activity with improved heterogeneous electron transfer rate. These features can be attributed to the high conductivity of porous N-LSG (down to 2.8 Ω per square) and its enriched active edge-plane sites. Furthermore, the N-LSG electrodes were decorated with MXene/Prussian blue (Ti3C2Tx/PB) composite via a simple spray-coating process, designed for sensitive detection of analytes. The Ti3C2Tx/PB-modified N-LSG electrodes were functionalized with catalytic enzymes for detecting glucose, lactate, and alcohol. The enzyme/Ti3C2Tx/PB/N-LSG electrodes exhibited remarkably enhanced electrochemical activity toward the detection of these biomarkers with a performance on par with previously reported on-chip carbon-based biosensors. Therefore, these materials have high potential for applications in personalized healthcare.

Reagentless fabrication of a porous graphene-like electrochemical device from phenolic paper using laser-scribing

This study fabricated a portable, high-performance, and reagentless electrochemical devices using CO2 laser-scribing process, which allowed localized carbonization of a non-conductive and low-cost polymer platform, i.e., phenolic-paper. The carbonized material was extensively characterized by Raman spectroscopy, XPS, XRD, SEM, and electrochemical impedance spectroscopy. The carbon-based electrodes were obtained from the photothermal process induced by CO2 laser radiation and subsequently subjected to electrochemical treatment to fabricate a functional material with excellent conductivity and low charge-transfer resistance. Additionally, the laser-scribed electrodes presented a porous structure with graphene-like domains, thus indicating both potential for on-site electroanalytical applications and better performance than conventional carbon electrodes.

Laser scribing of Cd2SnO4-based CdTe polycrystalline solar cells

Cd2SnO4-based CdTe solar cell is a potential technology to fabricate low cost and highly efficient thin film photovoltaic modules due to the excellent optical and electrical properties of Cd2SnO4 conductive transparent layer. However, the detailed research on patterning process is still deficient. In the present work, we developed laser scribing techniques to pattern the Cd2SnO4 thin film and the functional layers on top of the transparent conductive layer. By modifying the process and precisely adjusting the average energy density, the technique was further optimized to remove the upper layers completely without inducing any damage to the Cd2SnO4. The laser scribing process eliminates the exaggerated current density of CdTe solar cells contributed by the light absorption of the residual upper layers and as a result, device performance of the laser scribed cells could be precisely characterized. Besides, the isolative laser scribing of Cd2SnO4 layer and layers on top of Cd2SnO4 (window layer, absorption layer, back contact and metal electrode) is equal to the so-called P1, P2 and P3 steps in thin-film PV module production, which suggests that the whole set of laser scribing technique is applicable to the mass production of the Cd2SnO4-based CdTe solar cell modules.

Improvement of light extraction for AlGaN-based near UV LEDs with flip-chip bonding fabricated on grooved sapphire substrate using laser ablation

Mesh-textured flip-chip (FC) structures of AlGaN-based near ultraviolet-light-emitting diodes (NUV- LEDs) are fabricated using an Nd:YAG laser scriber. Compared with the output power of the reference FC-LEDs, those of conventional sapphire substrate (CSS) FC-LEDs and the patterned sapphire substrate FC-LEDs with laser-scribed mesh-textured backsides were improved by 28.7% and 7.2%, respectively. The CSS FC-LED is enhanced using the mesh-textured trench pattern attributable to an increase in the light-extraction efficiency resulting from an increase in the photon-escape probability due to enhanced light scattering at the trench-patterned-sapphire/air interface. Furthermore, the current–voltage curves depict that the laser scribing process does not adversely affect the electrical properties of the FC-LEDs. A Trace-Pro simulation revealed that the laser-scribed-trench CSS FC-LED is effective for light extraction.

Fabrication of Graphene/MoS2 Nanocomposite for Flexible Energy Storage

In the present work,MoS2 decorated graphene nanocomposite powders were synthesized by laser scribing method.Theobtainedflexible light-scribed graphene/MoS2composites are very suitableas micro-supercapacitors and thus their performance was evaluated at different concentrations.The effect of laser scribing process to reducegraphene oxide (GO) was investigated. The GO/MoS2composite wassynthesized using a chemical mixing of GO solution withMoS2/Dimethylformamide (DMF)solution.Themixtures with various concentrations of MoS2were then coated on a LightScribe DVD disk and laser scribed to reduce GO and create aMoS2/laser-scribed graphene (LSG) composite. Four different concentrations of MoS2/LSG composites (pristine rGO, 1:100, 1:75 and 1:50 MoS2/LSG) were utilized as supercapacitor electrode and the electrode with the best performance was selected for flexible micro-supercapacitor applications. The present findingsdemonstrate that MoS2/LSGmicro-supercapacitor has high specific capacitance per area. The sample with MoS2/LSGvolume ratio of 1:50 shows the highest specific capacitance (~ 8 Fcm-3) and itscyclic stabilityis favorable over 1000 cycles. Keywords:Graphene oxide, laser scribed graphene,MoS2/LSG nanocomposite, micro-supercapacitor, RGO, Microstructure, DVD.

Highly Tunable and Scalable Fabrication of 3D Flexible Graphene Micropatterns for Directing Cell Alignment.

Patterning graphene allows to precisely tune its properties to manufacture flexible functional materials or miniaturized devices for electronic and biomedical applications. However, conventional lithographic techniques are cumbersome for scalable production of time- and cost-effective graphene patterns, thus greatly impeding their practical applications. Here, we present a simple scalable fabrication of wafer-scale three-dimensional (3D) graphene micropatterns by direct laser tuning graphene oxide reduction and expansion using a LightScribe DVD writer. This one-step laser-scribing process can produce custom-made 3D graphene patterns on the surface of a disk with dimensions ranging from microscale up to decimeter scale in about 20 min. Through control over laser-scribing parameters, the resulting various 3D graphene patterns are exploited as scaffolds for controlling cell alignment. The 3D graphene patterns demonstrate their potential to biomedical applications, beyond the fields of electronics and photonics, which will allow to incorporate flexible graphene patterns for 3D cell or tissue culture to promote tissue engineering and drug testing applications.

Laser Patterning a Chem-FET Like Device on a V2O5Xerogel Film

Vanadium pentoxide xerogel films deposited onto gold microelectrodes were micropatterned by thermally induced conversion into crystalline α-V 2 O 5 , using optical lithography written at the focus of a confocal Raman microscope. The laser scribing process improved the electric contact and promoted the n-doping of the film with V IV ions. In this way, a field effect transistor like device was constructed and successfully applied as humidity sensor, where the combined lithographic design and the application of a negative back gate field (V G = -10.0 V) boosted the source-drain current by a hundred times, leading to a large gain in sensitivity.

Electrospun Mat of Poly(vinyl alcohol)/Graphene Oxide for Superior Electrolyte Performance.

Here, we describe an electrospun mat of poly(vinyl alcohol) (PVA) and graphene oxide (GO) as a novel solid-state electrolyte matrix, which offers better performance retention upon drying after infiltrated with aqueous electrolyte. The PVA-GO mat overcomes the major issue of conventional PVA-based electrolytes, which is the ionic conductivity decay upon drying. After exposure to 45 ± 5% relative humidity at 25 °C for 1 month, its conductivity decay is limited to 38.4%, whereas that of pure PVA mat is as high as 84.0%. This mainly attributes to the hygroscopic nature of GO and the unique nanofiber structure within the mat. Monolithic supercapacitors have been derived directly on the mat via a well-developed laser scribing process. The as-prepared supercapacitor offers an areal capacitance of 9.9 mF cm-2 at 40 mV s-1 even after 1 month of aging under ambient conditions, with a high device-based volumetric energy density of 0.13 mWh cm-3 and a power density of 2.48 W cm-3, demonstrating great promises as a more stable power supply for wearable electronics.

Single‐Step Reagentless Laser Scribing Fabrication of Electrochemical Paper‐Based Analytical Devices

AbstractA single‐step laser scribing process is used to pattern nanostructured electrodes on paper‐based devices. The facile and low‐cost technique eliminates the need for chemical reagents or controlled conditions. This process involves the use of a CO2 laser to pyrolyze the surface of the paperboard, producing a conductive porous non‐graphitizing carbon material composed of graphene sheets and composites with aluminosilicate nanoparticles. The new electrode material was extensively characterized, and it exhibits high conductivity and an enhanced active/geometric area ratio; it is thus well‐suited for electrochemical purposes. As a proof‐of‐concept, the devices were successfully employed for different analytical applications in the clinical, pharmaceutical, food, and forensic fields. The scalable and green fabrication method associated with the features of the new material is highly promising for the development of portable electrochemical devices.