Laser Firing Research Articles

PD45-03 FACTORS AFFECTING HOLMIUM LASER INEFFICIENCY: COMPARISON OF LARYNGEAL MASK AIRWAY AND ENDOTRACHEAL TUBE USE DURING FLEXIBLE URETEROSCOPY FOR RENAL STONES

You have accessJournal of UrologyCME1 Apr 2023PD45-03 FACTORS AFFECTING HOLMIUM LASER INEFFICIENCY: COMPARISON OF LARYNGEAL MASK AIRWAY AND ENDOTRACHEAL TUBE USE DURING FLEXIBLE URETEROSCOPY FOR RENAL STONES David G. Gelikman, Amy M. Reed, Naren Nimmagadda, and Nicole L. Miller David G. GelikmanDavid G. Gelikman More articles by this author , Amy M. ReedAmy M. Reed More articles by this author , Naren NimmagaddaNaren Nimmagadda More articles by this author , and Nicole L. MillerNicole L. Miller More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000003358.03AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: Flexible ureteroscopy with laser lithotripsy (fURSL) has become the standard treatment option for many types of kidney stones, however, many inefficiencies exist that can potentially increase operative time and therefore risk of complications. During surgery, respiratory motion causes clinically significant movement of the kidneys which can defocus laser energy from the stone and require the surgeon to halt laser firing. This can be influenced by factors such as BMI and airway securement by endotracheal tube (ETT) or laryngeal mask airway (LMA). Newer Lumenis Pulse™ 120H holmium lasers provide access to previously unavailable intraoperative data including timestamps and duration of pauses between laser activation. We sought to utilize this data to calculate a “lasing inefficiency” percentage for each case to objectively identify surgical and anthropometric factors associated with decreased operative efficiency. METHODS: A total of 48 intraoperative reports and patient data sets were analyzed from an ongoing laser lithotripsy clinical trial which includes metrics such as age, sex, race, BMI, and kidney stone characteristics. Ureteroscopy in each case was performed by a fellowship-trained, attending endourologist. Lasing activation start times and duration were used to calculate pauses between each laser firing. Pauses longer than 30 seconds long were excluded to account for navigation to a different site or change of instrumentation. The total lasing pause time was divided by the total lasing duration to yield a “lasing inefficiency” percentage for every case. Both multivariate and univariate analysis was performed to compare lasing inefficiency to patient demographics, anesthesia administration, and stone burden. RESULTS: Patients who received an LMA had significantly higher lasing inefficiency (26.5%) compared to those who received ETT intubation (20.7%) in the univariate analysis (p<0.05) as well as in the multivariate model. There were no significant differences in lasing inefficiency for the other study variables. Though BMI was not found to be significantly correlated with lasing inefficiency, we noted that high patient BMI was significantly correlated with use of ETT over LMA. CONCLUSIONS: Our data supports the use of ETT over LMA to reduce lasing inefficiency when using Holmium lasers in fURSL. However, it remains one consideration among many when choosing between utilizing an LMA or ETT. Source of Funding: This project was supported by the Endourological Society 2022 Summer Student Scholarship. © 2023 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 209Issue Supplement 4April 2023Page: e1163 Advertisement Copyright & Permissions© 2023 by American Urological Association Education and Research, Inc.MetricsAuthor Information David G. Gelikman More articles by this author Amy M. Reed More articles by this author Naren Nimmagadda More articles by this author Nicole L. Miller More articles by this author Expand All Advertisement PDF downloadLoading ...

Simultaneous measurement of carbon emission and gas temperature via laser-induced breakdown spectroscopy coupled with machine learning.

A method, which can accurately measure carbon emission and gas temperature simultaneously in real-time from a laser-induced breakdown spectrum (LIBS) via machine learning, is proposed in this study. In typical, peak intensity ratios had been used to map species concentrations prior to plasma formation, after removing the broadband continuum of the spectrum; however, the dependence of these peak intensity ratios on the concentration changes with the change in gas density. Therefore, considering the fact that the strength and shape of this broadband continuum is a function of the gas density for a given optical setup, we attempted to collect a spectrum by shortening the time delay after the laser fire, such that the spectrum can contain some of the broadband continuum. Since the analytical quantification of this broadband continuum is not trivial, we employed a machine learning approach to acquire a model that simultaneously predicts the gas temperature and CO2 concentration. The predictive performance of the model trained with spectra that contain the broadband continuum was much better than that without it; the gradient-weighted regression activation mapping (Grad-RAM) analysis revealed that the model utilizes the broadband spectrum for temperature prediction and correction of changes in peak intensity due to temperature changes in the concentration prediction process.

Satellite laser ranging at ultra-high PRF of hundreds of kilohertz all day

Satellite laser ranging (SLR) had been operated at a pulse repetition frequency (PRF) from ∼10 Hz to 10 kHz; the ultra-high PRF of SLR (UH-SLR) is a trend of development. In this study, an alternate working mode of laser firing and gated pulse bursts is proposed to solve the problem of laser echo interference by laser backscattering. Through an ultra-high PRF of 200-kHz picosecond green laser with single-pulse energy of 80 μJ and a pulse width of 10 ps and a ranging gate device, UH-SLR has been built by an aperture of the 60-cm SLR system in the Shanghai Astronomical Observatory. By this UH-SLR, low-orbit to high-orbit and geostationary orbit satellites are measured night and day and also for low-orbit and medium-orbit satellites in the daytime. The normal point (NP) accuracy is ∼30 μm for low-orbit satellites and ∼100 μm for high-orbit satellites, which provides an effective method for the development of ultra-high PRF and high-precision space target laser ranging.

Effect of using laser incising treatment and fire-retardant coating on Larix kaempferi wood to improve fire retardant performance

To improve fire-retardant performance of Japanese larch (Larix kaempferi) wood, this study analyzed the effect of pinholes made by laser incising and fire retardant (FR) coating on the surface of Japanese larch wood. Combustion properties such as peak heat release rate (PHRR) and total heat release (THR) of Japanese larch and Korean red pine (Pinus densiflora) wood without FRs showed similar tendencies. The comparison of the combustion properties on wood injected with an inorganic water-soluble FR under vacuum revealed that the PHRR and the THR of Korean red pine wood decreased by 37 and 62%, respectively. FR was injected into the Japanese larch specimens with pinholes on the surface and additionally coated with 5% sodium silicate and 35% potassium bromide. The results indicated a 16 to 25 and 19% reduction in PHRR and THR, respectively, compared to those without the FR. Despite the pinholes and FR coating, the FR employed in this study did not meet the standards set in Korea (THR of 8 MJ/m2). This study serves as a reference for future studies on the application of pressurized conditions and other surface treatments to improve the FR percent injection and performance of Japanese larch wood.

A method for reducing thermal injury during the ureteroscopic holmium laser lithotripsy

ObjectiveMany studies have demonstrated the heat effect from the holmium laser lithotripsy can cause persistent thermal injury to the ureter. The purpose of this study was to elucidate the use of a modified ureteral catheter with appropriate firing and irrigation to reduce the thermal injury to the “ureter” during the ureteroscopic holmium laser lithotripsy in vitro. MethodsAn in vitro lithotripsy was performed using a modified catheter (5 Fr) as the entrance for the irrigation and the holmium laser fiber while using the remaining space in the ureteroscopic channel as an outlet. Different laser power settings (10 W, 20 W, and 30 W) with various firing times (3 s, 5 s, and 10 s) and rates of irrigation (15 mL/min, 20 mL/min, and 30 mL/min) were applied in the experiment. Temperature changes in the “ureter” were recorded with a thermometer during and after the lithotripsy. ResultsDuring the lithotripsy, the local highest mean temperature was 60.3 °C and the lowest mean temperature was 26.7 °C. When the power was set to 10 w, the temperature was maintained below 43 °C regardless of laser firing time or irrigation flow. Regardless of the power or firing time selected, the temperature was below 43 °C at the rate of 30 mL/min. There was a significant difference in temperature decrease when continuous 3 s drainage after continuous firing (3 s, 5 s, or 10 s) compared to with not drainage (p<0.05) except for two conditions of 0.5 J×20 Hz, 30 mL/min, firing 5 s, and 1.0 J×10 Hz, 30 mL/min, firing 5 s. ConclusionOur modified catheter with timely drainage reducing hot irrigation may significantly reduce the local thermal injury effect, especially along with the special interrupted-time firing setting during the simulated holmium laser procedure.

PD19-04 NOBODY LIKES BURNT POPCORN: THE MOST EFFICIENT POPCORNING SETTINGS IN A NOVEL 3D-KIDNEY MODEL THAT LIMITS THERMAL INJURY

You have accessJournal of UrologyCME1 May 2022PD19-04 NOBODY LIKES BURNT POPCORN: THE MOST EFFICIENT POPCORNING SETTINGS IN A NOVEL 3D-KIDNEY MODEL THAT LIMITS THERMAL INJURY Christian Tabib, Zachary Dionise, Sabrina Tran, Francois Soto-Palou, Pei Zhong, Glenn Preminger, and Michael Lipkin Christian TabibChristian Tabib More articles by this author , Zachary DioniseZachary Dionise More articles by this author , Sabrina TranSabrina Tran More articles by this author , Francois Soto-PalouFrancois Soto-Palou More articles by this author , Pei ZhongPei Zhong More articles by this author , Glenn PremingerGlenn Preminger More articles by this author , and Michael LipkinMichael Lipkin More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000002557.04AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: When stone popcorning, the use of higher energy with little to no irrigation is preferred. However, this combination of high power with low flow can lead to increased risk of thermal damage with longer laser firing times. Using predetermined lasering and irrigation ‘cool down’ durations within a novel, anatomically accurate 3D kidney model, our aim was to identify the laser settings that produce the most efficient popcorning without reaching thermal dose (t43) that causes tissue damage. METHODS: Hard Begostone phantoms, mimicking calcium oxalate monohydrate stones, were crushed and sieved to 2-4mm fragments. Fragments were then separated by size measuring 2-2.8mm, 2.8-3.35mm, and 3.35-4mm and mixed by mass at a ratio of 2:2:1, respectively. Approximately 0.5g of fragments were placed in the upper pole of our anatomical 3D-printed kidney model. Each triplicate trial consisted of iterative laser/irrigation cooling cycles for two minutes using a MosesTM 120H 2.0 laser (Table). Laser firing and cooling times were determined by measuring t43 with each laser setting, allowing for maximal laser to cooling ratio that would not exceed tissue injury threshold (t43 70 min). After treatment, stones were dried and sieved into <1mm, 1-2mm, 2-2.8mm, 2.8-3.35, and 3.35-4mm fragments, which were then weighed. Ablation efficiency was calculated as post-treatment mass <1mm, with comparisons by ANOVA and Tukey post-hoc tests. RESULTS: Overall, the most efficient setting was 0.5J/90Hz with no irrigation; while the most efficient setting using low irrigation were 0.4J/110Hz and 0.5/J/80Hz SP (Figure). Even with shorter laser times, popcorning was more efficient with no irrigation, especially at high powers (all p<0.05). CONCLUSIONS: When accounting for thermal dose, 0.5J/90Hz without irrigation provides the most efficient popcorning, despite shorter laser times. When thermal injury is of special concern and the surgeon prefers low flow, 0.4J/110Hz appears most efficient. Last, if extended frequency is unavailable, 0.6J/80Hz without irrigation should be used. Source of Funding: None © 2022 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 207Issue Supplement 5May 2022Page: e350 Advertisement Copyright & Permissions© 2022 by American Urological Association Education and Research, Inc.MetricsAuthor Information Christian Tabib More articles by this author Zachary Dionise More articles by this author Sabrina Tran More articles by this author Francois Soto-Palou More articles by this author Pei Zhong More articles by this author Glenn Preminger More articles by this author Michael Lipkin More articles by this author Expand All Advertisement PDF DownloadLoading ...

Using Kiln Boats to Reuse Marine Plastics

Microplastics are the biggest pollutants in marine ecosystems. Each year, over 8 million tons of plastic enter the oceans. Via microbes, microplastics may transport toxic chemicals into food webs. It is therefore important to create a way to remove microplastics and reduce the impact of microplastics on the ocean’s food web. This paper discusses the plan of using kiln firing, laser firing, pollution control, and green energy production to reuse marine plastics. We used a wood-fired kiln to design a kiln boat. The “Patch” is a large ocean area with trash. The calorific value of plastics is comparable to that of fuels, around 40 MJ/kg. This makes plastic a good fuel for ceramic firing. Based on our Taiwanese invention patent for a laser ceramic firing technique (Taiwan, R.O.C Patent Number: I687394 and I750055), we integrated a variety of ceramic technologies to address the problem of marine plastic pollution. A kiln boat is a good plan. Creating a moveable kiln not only reduces transportation costs but also reuses the calorific value of plastics. This is important in guiding future marine litter research and ocean cleanup management strategies.

Evaluation of Probiotic-Fermented Feed Addition and LaserFiring to Accelerate Mature Broodstocks and Seed Productions of African Catfish (Clarias gariepinus)

This study aimed to determine the effects of fermented feed using probiotics and laser-firing to accelerate the mature broodstocks and seed productions of African catfish (Clarias gariepinus). Fish has used male and female broodstocks of catfish. The method was used a completely randomized design with three treatments: unfermented feed as control, probiotic-fermented feed (PFF), and probioticfermented feed+laser firing (PFF+Li). In the first study, a laser-firing dose of 1.125 Joule was performed on fish broodstocks every 15 days. The gonadal maturity time of male and female broodstocks was observed. The second study, treated female broodstocks, was mated with mature male broodstocks without any prior treatments (control). Fertilization rate, hatching rate, and seed production performances such as survival rate and total length were measured. The results showed that treatment of PFF+Li has a significant effect (P&lt;0.05) on the gonadal maturity time of males and females. This treatment reaches the fastest time to mature of the female gonad (31-41 days) and the male gonad (32-37 days) than other treatments (P&lt;0.05). This treatment also produced the highest fertilization, hatching, and survival rates of more than 90%, respectively, and the highest seed yield of 2.1-3.0 cm size compared to other treatments (P&lt;0.05) in African catfish.

Drone Detection and Auto Destroy System

The purpose of this project is to design and construct automatic drone detection and destroying system using embedded systems. This system is designed to detect the target (drone) moving in multiple directions. The target destroying system moves automatically in the direction of drone and fires it upon fixing the target. In this project we are making use of infrared sensor based radar system and a dc motor driven laser firing unit interfaced with a microcontroller based control unit. Embedded C programming is used for Microcontroller.

Small All-Range Lidar for Asteroid and Comet Core Missions

We report the development of a new type of space lidar specifically designed for missions to small planetary bodies for both topographic mapping and support of sample collection or landing. The instrument is designed to have a wide dynamic range with several operation modes for different mission phases. The laser transmitter consists of a fiber laser that is intensity modulated with a return-to-zero pseudo-noise (RZPN) code. The receiver detects the coded pulse-train by correlating the detected signal with the RZPN kernel. Unlike regular pseudo noise (PN) lidars, the RZPN kernel is set to zero outside laser firing windows, which removes most of the background noise over the receiver integration time. This technique enables the use of low peak-power but high pulse-rate lasers, such as fiber lasers, for long-distance ranging without aliasing. The laser power and the internal gain of the detector can both be adjusted to give a wide measurement dynamic range. The laser modulation code pattern can also be reconfigured in orbit to optimize measurements to different measurement environments. The receiver uses a multi-pixel linear mode photon-counting HgCdTe avalanche photodiode (APD) array with near quantum limited sensitivity at near to mid infrared wavelengths where many fiber lasers and diode lasers operate. The instrument is modular and versatile and can be built mostly with components developed by the optical communication industry.

543 Does the time of laser usage during surgery for twin-twin transfusion syndrome impact pregnancy outcomes?

Selective fetoscopic laser photocoagulation (SFLP) performed in twin-twin transfusion syndrome (TTTS) results in placental perfusion changes. Our objective is to evaluate pregnancy outcome in relation to the time of laser firing during surgery. Retrospective cohort study at a single fetal center of all TTTS patients treated with SFLP from April 2010 to June 2019. At the time of surgery, the time of laser firing was documented. Data collected was maternal demographic data, pregnancy characteristics and outcomes, surgical characteristics, fetal survival, and postoperative complications. Laser time was not normally distributed, thus the upper quartile (7.6 minutes (mins)) was selected as the cut-off for increased laser time. Primary outcomes were pregnancy outcomes, including survival and risk of preterm birth (PTB) at ≤26, 28, and 32 weeks. Data was analyzed using chi2, student’s t-test, multivariate logistic regression, and linear regression as appropriate. 580 patients met inclusion criteria. Median laser time was 4.9 min (range 0.2-22 min). Baseline characteristics were similar amongst groups (table). Surgery laser time >7.6 min was significantly associated with increase in number of total vessels ablated, higher rate of microseptostomy (39% vs 26%, p < 0.001), higher laser energy level (17298 vs 8608 joule, p < 0.001), and lower donor survival (71% vs 82% p = 0.004) as compared to time <7.6min respectively. Laser time <7.6min was also associated with higher rates of double survival (81.7% vs 70.1%, respectively, p = 0.034). Surgery laser time was not associated with any increased risk of PTB prior to 26, 28, and 32 weeks. Longer surgery laser time >7.6 min was associated with significant decrease in donor and double fetal survival rate. Surgery laser time did not impact gestational age at delivery. This information becomes important in surgical training for SFLP and patient counseling.View Large Image Figure ViewerDownload Hi-res image Download (PPT)

Laser-Powered Co-Firing Process for Highly Efficient Si Solar Cells

This article presents a successful laser-powered co-firing process for highly efficient Si solar cells as a more compact and energy-efficient alternative to the conventional firing process in an infrared (IR) lamp-powered heat chamber. The best cell group reaches with laser firing only 0.1%abs lower cell efficiency compared to the best group with conventional firing, demonstrating the industrial potential of this laser firing technology. Adding the laser enhanced contact optimization (LECO) process after firing improves the cell efficiency for laser firing to the level of conventional firing, demonstrating the potential of the combination of the laser firing and the LECO process.

Analysis of Surface Passivation and Laser Firing on Thin-Film Silicon Solar Cells Via Light-Beam Induced Current

Liquid phase crystallized silicon solar cells on glass have recently demonstrated 15.1% efficiency using a heterojunction interdigitated back contact cell architecture and an absorber thickness of 14 $\mu$ m. One of the key enabling developments was a new method to first passivate electron contact fingers with a-Si:H(i) and then locally laser fire them to maintain a low contact resistance. In this work, high resolution, light-beam induced current measurements (LBIC) were used to analyze this approach. Charge collection was observed to have increased from 0.13 ${\text{mAcm}}^{-2}$ to 0.9 ${\text{mAcm}}^{-2}$ under the electron contact which is a sevenfold increase. Using 520, 642, 932, and 1067 nm wavelengths of incident light, external quantum efficiency was mapped in regions including grain boundaries, dislocation defects, shunts, defect-free regions, and laser fired spots. Reduction of charge collection in the laser fired spots was limited to diameters of 50–20 $\mu$ m, depending on whether electrical recombination or optical losses dominated. Effective minority carrier diffusion length under the majority carrier contacts was obtained by fitting of LBIC measurements. It was observed to have improved from 20.5 $\mu$ m to 22.7–40.4 $\mu$ m and up to 89.0 $\mu$ m in the best case. Based on this, wider contact fingers and improved surface passivation at the electron contact is encouraged in the near future to achieve efficiencies $\geq$ 16%.

A Versatile Platform for Mass Spectrometry Imaging of Arbitrary Spatial Patterns.

A vision-system driven platform, RastirX, has been constructed for mass spectrometry imaging (MSI) of arbitrary two-dimensional patterns. The user identifies a region of interest (ROI) by drawing on a live video image of the sample with the computer mouse. Motion commands are automatically generated to move the sample to acquire scan data for the pixels in the ROI. Synchronization of sample stage motion with laser firing and mass spectrometer (MS) scan acquisition is fully automated. RastirX saves a co-registered optical image and the scan location information needed to convert raw MS data into imzML format. Imaging an arbitrarily shaped ROI instead of the minimal enclosing rectangle reduces contamination from off-sample material and significantly reduces acquisition time.

Thermal effect of holmium laser during ureteroscopic lithotripsy

BackgroundHolmium laser lithotripsy is the most common technique for the management of ureteral stone. Studies founded that holmium laser firing can produce heat which will cause thermal injury towards ureter. The aim of our current study is to explore factors affecting thermal effect of holmium laser during ureteroscopic lithotripsy.MethodsAn in vitro experimental model is design to simulate the ureteroscopic lithotripsy procedure. Different laser power settings (10w (0.5JX20Hz, 1.0 JX10Hz), 20w (1.0 JX20Hz, 2.0 JX10Hz), 30w (1.5JX20Hz, 3.0 JX10Hz)) with various firing time (3 s, 5 s, 10s) and irrigation flow rates(10 ml/min, 15 ml/min, 20 ml/min and 30 ml/min) were employed in the experiment. The temperature around the laser tip was recorded by thermometer.ResultsThe temperature in the “ureter” rises significantly with the increasing laser power, prolonging firing time and reducing irrigation flow. The highest regional temperature is 78.0 °C at the experimental set-up, and the lowest temperature is 23.5 °C. Higher frequency setting produces more heat at the same power. Laser power < =10w, irrigation flow> = 30 ml/min and “high-energy with low-frequency” can permit a safe working temperature.ConclusionWe clarify that the thermal effect of holmium laser is related with both laser working parameters and irrigation flow. The proper setting is the key factor to ensure the safety during ureteroscopic holmium laser lithotripsy.

How to reduce 'double-firing'-induced scope damage by investigating the relationship between laser fiber core degradation and fiber jacket burn?

Purpose'Double-firing effect' in which laser firing occurs in the fiber tip and its proximal part is caused by different breakdown rates between fiber jackets and cores. This study investigated a new safe distance concept to prevent scope damage by analyzing the breakdown of the laser fiber jacket and cores.MethodsLaser fibers were fixed in a benchtop simulation model. The fiber tip was in contact with uniform phantom stones and submerged in saline. Four different energy settings (1.0 or 2.0J x 10Hz or 30Hz) and two different fiber sizes (200 μm and 365 μm) were tested. After three minutes of use at each energy setting, the length of fiber shortening and jacket burn were measured. The fibers were stripped to measure the length of core degradation.ResultsMean degradation lengths were 4.2 to 7.8 mm. There was no statistical difference in the mean lengths of fiber core degradation and jacket burn. However, core degradation was longer than the jacket burn in half of the samples. The mean difference in lengths between core degradation and jacket burn was 0.49 ± 0.90 mm. Lengths of core degradation and the jacket burn were longer at the setting of high-power energy and 200 μm fiber - 2J with 30 Hz.ConclusionTo reduce ‘double-firing’-induced damage, the authors recommend that laser fiber should be cut 1.0 mm longer than visible jacket burn at high-power settings after 3-min continuous fragmentation. After cutting the fiber, the laser should be checked whether ‘double-firing’ is no more seen.

MP15-18 INVISIBLE THREAT TO FLEXIBLE URETEROSCOPE – ‘DOUBLE FIRING’ BY LASER FIBER CORE DEGRADATION

INTRODUCTION AND OBJECTIVE:The authors found so-called 'Double firing' phenomenon in which laser firing occurred not only in the laser fiber tip but also in its proximal part, and assuming that thi...

Toward High Solar Cell Efficiency with Low Material Usage: 15% Efficiency with 14 μm Polycrystalline Silicon on Glass

Liquid‐phase‐crystallized silicon (LPC‐Si) is a bottom‐up approach to creating solar cells with the potential to avoid material loss and energy usage in wafer slicing techniques. A desired thickness of silicon (5–40 μm) is crystallized with a line‐shaped energy source, which is a laser, herein. The first part reports the efforts to optimize amorphous silicon contact layers for better surface passivation. The second part covers laser firing on the electron contact. It enables a controllable trade‐off between charge collection and fill factor (FF) by creating a low resistance contact, while preserving a‐Si:H (i) passivation in other areas. Short‐circuit current density (JSC) is observed to be up to 33:1 mA cm−2, surpassing all previously reported values for this technology. Open‐circuit voltage (VOC) of up to 658 mV also exceeded every previous value published at a low bulk doping concentration (1 × 1016 cm−3). Laser firing reduced JSC by 0:6 mA cm−2 on average but improved the FF by 22.5% absolute on average, without any significant effect on VOC. Collectively, these efforts have helped in achieving a new in‐house record efficiency for LPC‐Si of 15.1% and show a potential to reach 16% efficiency in the near future with optimization of series resistance.

FEASIBILITY STUDY OF MICRO-LATTICE STRUCTURES BY MULTIPHOTON LITHOGRAPHY

The paper describes the possibilities of additive manufacturing with multiphoton lithography. The basis of this technology is that a laser beam (with a certain wavelength) is fired into the mixture of a monomer and a photo-initiator. When the energy of the laser is high enough, the latter acts as a catalyser for the polymerization of the monomer compound. This study focuses on the influences of certain parameters of the multiphoton lithography process. One of the important aspects is the choice of the solvent for the post processing. In sequence to the solvent problem, the influence of the layer height is examined. Furthermore the limits and possibilities of the setup in use are investigated. As an example the differences in fabrication with the laser firing with "constant frequency" and "constant density" were subject of this investigation. The second goal of the study was to compare three different structures consisting of periodically repeating elements, scaled in size and number of elements per side.

Laser firing in silicon heterojunction interdigitated back contact architecture for low contact resistance

This work reports a laser firing technique applied to completed silicon heterojunction interdigitated back contact solar cells in order to lower contact resistance. Previously, the implementation of a-Si:H(i) at the electron contact of polycrystalline silicon solar cells on glass substrates led to an increase in series resistance. The cell architecture with the current record efficiency of 14.2% (with illumination through glass) utilizes only an a-Si:H(n+) layer and 2–2.9 mA cm−2 of short circuit current density is lost due to electrical shading under the electron contact [1,2]. The goal of implementing an a-Si:H(i) layer and laser firing at this contact is to achieve low contact resistance at fired spots while preserving a-Si:H(i) passivation in unfired regions. After the laser firing, VOC was retained, while up to 14% absolute increase in FF was obtained with a mere 0.2 mA cm−2 loss in JSC. In the best performing cell, a 72.1% FF was achieved with a 0.7 mA cm−2 loss in JSC. Two laser sources were used to first ablate a part of the silver contact metal, and then to laser fire through the Si(n)/a-Si:H(i/n+)/ITO/Ag contact. The optimal laser fluence was found to be 1.1–0.5 J cm−2 (355 nm, picosecond pulse duration) and 4.4–5.2 J cm−2 (532 nm, nanosecond pulse duration), respectively. The upper limit on specific contact resistance in the laser fired spots was calculated to be 38±20mΩcm2 as a conservative estimate.