Finger Width Research Articles

Flexible, planar integratable and all-solid-state micro-supercapacitors based on nanoporous gold/ manganese oxide hybrid electrodes via template plasma etching method

Along with the rapid development of miniaturization of mobile devices and wearable integrated electronics system, flexible integrated micro electrical energy storage devices with high-performance, deformability and cycling stability will be the technological trend for a long time in the future. In this work, template plasma etching method and electrochemical deposition method have been combined to fabricate nanoporous gold/manganese oxide interdigitated electrodes that can be easily utilized in flexible micro-supercapacitors(MSCs). These MSCs exhibit relatively high specific capacitance of 18.47 mF cm−2 in 0.5 M Na2SO4 electrolyte and 11.58 mF cm−2 in polyvinyl alcohol (PVA)/LiCl solid state electrolyte. A high energy density of 6.93 × 10−7 Wh cm−2 to 1.03 × 10−6 Wh cm−2 while power density ranging from 4.63 × 10−5 W cm−2 to 3.12 × 10−4 W cm−2. The NPG/MnO2 MSCs excellent long term cycling stability of 80.7% can be seen even after cycling for 5000 times. Moreover, the MSCs devices also demonstrate a sound flexibility and a superior frequency response (1.25 ms). In addition, the effects of various finger width and finger spacing on performance are compared, the critical importance of adjusting interdigitated structure is highlighted. This present research may provide an innovative avenue for the new prospective high-performance flexible micro-supercapacitors.

<b><I>Nyctibatrachus mewasinghi</I>, a new species of night frog (Amphibia: Nyctibatrachidae) from Western Ghats of Kerala, India</b>

A new species Nyctibatrachus mewasinghi is described from the Malabar Wildlife Sanctuary of Western Ghats of Kozhikode District, Kerala. The new species can be distinguished from known congeners based on small adult size, head equal to or slightly wider than long, less wrinkled dorsal skin with prominent granular projections, absence of dorso-lateral glandular folds, a ridge extending from the lip over the tip of the snout to between the nostrils bifurcate posteriorly producing an inverted ‘Y’, finger and toe discs well developed with dorso-terminal groove, cover rounded distally, third finger disc slightly wider than finger width and fourth toe disc almost equal to or slightly wider than toe width, presence of two palmar tubercles, moderate webbing and thigh, shank and foot almost of equal length. Molecular phylogeny based on two mitochondrial genes (ND1 and 16S rRNA) reveals that the species is genetically distinct from others within the genus, and is a sister taxon to N. athirappillyensis and N. kempholeyensis. Multivariate morphometric analysis clearly distinguishes the new night frog species Nyctibatrachus mewasinghi from N. athirappillyensis and N. kempholeyensis.

GaN Membrane Supported SAW Pressure Sensors With Embedded Temperature Sensing Capability

This paper presents the fabrication and characterization of a GHz operating surface acoustic wave (SAW)-based pressure sensor on a 1.2- $\mu \text{m}$ -thin GaN membrane. Two types of interdigitated transducers are manufactured using electron beam nanolithography to obtain finger and interdigit spacing widths, one with 170 nm and the other 200-nm-half pitch. Micromachining techniques are used to obtain the 1.2- $\mu \text{m}$ -thin membrane. The resonance frequency shift of the SAW, the pressure sensitivity, $s_{p}$ , as well as the pressure coefficient of frequency (PCF), were experimentally determined and analyzed, both for the Rayleigh as well as for the symmetrical Lamb propagation mode, in the 1 to 7 Bar pressure range. Record values for $s_{p}$ (up to 6 MHz/Bar) and PCF (up to 537 ppm/Bar) have been obtained, especially for the symmetrical Lamb propagation mode also due to the very high frequency operation (5–11.5 GHz). The effect of different orientations of the SAW device (in the $\textrm {[1}\bar {\textrm {1}} \textrm {00]}$ and $\textrm {[11}\bar {\textrm {2}} \textrm {0]}$ directions) on the frequency response and sensitivity is also analyzed. The possibility to determine simultaneously the pressure and the temperature with the same SAW structure operating as a dual sensor has been demonstrated.

Flow instabilities due to the interfacial formation of surfactant-fatty acid material in a Hele-Shaw cell.

We present an experimental study of pattern formation during the penetration of an aqueous surfactant solution into a liquid fatty acid in a Hele-Shaw cell. When a solution of the cationic surfactant cetylpyridinium chloride is injected into oleic acid, a wide variety of fingering patterns are observed as a function of surfactant concentration and flow rate, which are strikingly different than the classic Saffman-Taylor (ST) instability. We observe evidence of interfacial material forming between the two liquids, causing these instabilities. Moreover, the number of fingers decreases with increasing flow rate Q, while the average finger width increases with Q, both trends opposite to the ST case. Bulk rheology on related mixtures indicates a gel-like state. Comparison of experiments using other oils indicates the importance of pH and the carboxylic head group in the formation of the surfactant-fatty acid material.

Excitation and time resolved spectroscopy of SAW harmonics up to GHz regime in photolithographed GaAs devices

In this work, we demonstrate the excitation of surface acoustic waves (SAW) harmonics up to GHz regime in photolitographed devices fabricated on gallium arsenide (GaAs) by acting on the IDT metallization ratio among the finger width and pitch. Specifically, we observed up to the 13th harmonic, which corresponds to a frequency of about 1.7 GHz. Moreover, we employed time-resolved spectroscopy for isolating the shape of the SAW bandpass-filter response (for each harmonic) eliminating the interference between acoustic and electromagnetic waves. Notably, the extracted SAW spectra are characterized by a bandwidth which remains constant for the different harmonic modes, unlike the case of traditional SAW filters (having a 0.5 metallization ratio) where the pass band increases with the working frequency. These results are relevant for applications where high frequencies and multiple harmonics excitation are desirable, or where quantitative measurements of the direct SAW signal are required.

Low‐Ohmic Contacting of Laser‐Doped p‐Type Silicon Surfaces with Pure Ag Screen‐Printed and Fired Contacts

The state‐of‐the‐art low‐ohmic electrical contacting of highly boron‐doped silicon surfaces is based on the use of screen‐printed and fired silver‐aluminum (Ag‐Al) contacts. For these contacts, metal crystallites with depths of up to a few microns are observed at the interface. For screen‐printed and fired Ag contacts on phosphorus‐doped surfaces, the observed crystallite depths are much smaller. In this work, low‐ohmic electrical contacting of local laser‐doped p‐type silicon surfaces with commercial pure Ag screen‐printing paste are demonstrated. The doping layer is based on the “pPassDop” approach, which serves as a passivation layer on the rear side of p‐type silicon solar cells. The specific contact resistances are measured down to 1 mΩ cm2 for p‐type doping densities of about 3 × 1019 cm−3 at the silicon surface and finger widths of around 55 μm. Microstructure analysis reveals the formation of numerous small Ag crystallites at the interface with penetration depths of less than 80 nm. A first implementation of the “pPassDop” approach on 6‐inch p‐type Cz‐Si bifacial solar cells using solely Ag contacts on both sides results in a peak front side energy conversion efficiency of 19.1%, measured on a black chuck with contact bars on both sides.

High-Resolution Graphene Films for Electrochemical Sensing via Inkjet Maskless Lithography.

Solution-phase printing of nanomaterial-based graphene inks are rapidly gaining interest for fabrication of flexible electronics. However, scalable manufacturing techniques for high-resolution printed graphene circuits are still lacking. Here, we report a patterning technique [i.e., inkjet maskless lithography (IML)] to form high-resolution, flexible, graphene films (line widths down to 20 μm) that significantly exceed the current inkjet printing resolution of graphene (line widths ∼60 μm). IML uses an inkjet printed polymer lacquer as a sacrificial pattern, viscous spin-coated graphene, and a subsequent graphene lift-off to pattern films without the need for prefabricated stencils, templates, or cleanroom technology (e.g., photolithography). Laser annealing is employed to increase conductivity on thermally sensitive, flexible substrates [polyethylene terephthalate (PET)]. Laser annealing and subsequent platinum nanoparticle deposition substantially increases the electroactive nature of graphene as illustrated by electrochemical hydrogen peroxide (H2O2) sensing [rapid response (5 s), broad linear sensing range (0.1-550 μm), high sensitivity (0.21 μM/μA), and low detection limit (0.21 μM)]. Moreover, high-resolution, complex graphene circuits [i.e., interdigitated electrodes (IDE) with varying finger width and spacing] were created with IML and characterized via potassium chloride (KCl) electrochemical impedance spectroscopy (EIS). Results indicated that sensitivity directly correlates to electrode feature size as the IDE with the smallest finger width and spacing (50 and 50 μm) displayed the largest response to changes in KCl concentration (∼21 kΩ). These results indicate that the developed IML patterning technique is well-suited for rapid, solution-phase graphene film prototyping on flexible substrates for numerous applications including electrochemical sensing.

Understanding the rear-side layout of p-doped bifacial PERC solar cells with simulation driven experiments

To investigate the rear side of bifacial p-type Czochraslki-grown silicon PERC solar cells, the present work combines Sentaurus Device simulation – calibrated with extensively characterized samples – and the subsequent fabrication of solar cells according to the simulation findings. The authors investigate the physical alteration of rear-side characteristics in the context of an additional rear-side illumination. The additional injection represents an further factor for the balance of carrier generation, recombination and series resistances which in turn influences the design rules for the rear side layout. Our detailed bifacial simulations include these physical aspects and we derive design solutions for different bifacial illumination scenarios for a bifacial p-doped PERC solar cell. Using an industrial PERC process, solar cells with laser contact openings (LCO) and a rear aluminum grid were produced according to the simulation results with a wide variation in rear side layout parameters. The PERC batches showed a rather constant medium (front side) efficiency of η = 20.8±0.2% and a bifaciality of 66 to 77% depending on the rear layout, allowing us to investigate the rear-side characteristics in detail and to compare them with the effects predicted by the simulations. We processed an aluminum rear contact grid with finger widths as small as 100 µm and successfully aligned it onto the LCO with 30 µm contact openings on full-area 156x156 mm2 wafers. We reached good accordance between the monofacial measurements from front and rear side and our simulation model and could thus predict bifacial illumination results by modeling for two issues: 1. Planar rear sides have an advantage over pyramid textured rear sides for 1000 W/m² front illumination unless additional rear illumination exceeds 250 W/m². 2. As soon as any rear illumination is added to the front-illuminated PERC solar cell, 100 µm thin fingers at the rear side have an output power advantage compared to 150 µm and 200 µm wide fingers.

Three-dimensional steady and transient fully coupled electro-thermal simulation of AlGaN/GaN high electron mobility transistors: Effects of lateral heat dissipation and thermal crosstalk between gate fingers

In this paper, we develop three-dimensional fully coupled electro-thermal (ET) simulation for AlGaN/GaN high electron mobility transistors (HEMTs), which is a relative complete and accurate simulation compared to the current existed simulations, capable of describing the lateral ET behavior of the device. As applications of this simulation, we investigate impact of the gate width (WG) and number of the gate fingers (NG) on the steady and transient ET behavior of the device. The steady results show that the lateral heat dissipation and thermal crosstalk between the gate fingers significantly affects the ET behavior for the device with narrow gate and multifinger, respectively. However, the transient results show that, within a time scale after the device switching on, the ET behavior is not influenced by WG and NG, i.e., the lateral heat dissipation and thermal crosstalk have no effects. This indicates that when the device operating in high frequency, increasing WG and NG to improve the power output is not restricted by the self-heating.

Co-diffused bi-facial PERT solar cells

The authors present a fully solderable, co-diffused and bi-facial PERT solar cell where the rear BSG/SiN stack acting both as dopant and passivation source reaching a mean efficiency of 20.4 %. The conductivity induced by the presence of the p+ layer at the rear reduces series resistance losses significantly by simultaneously enabling the use of lowly doped Si wafers that reduceB-O degradation while maintaining a high fill factor. Parallel processed, mono-facial pendants reach the same efficiency level. A higher FF for the mono-facials is compensated by a higher Voc for the bi-facial PERT devices. SEM analysis on test structures show an overall superior, local Al-Si contact in terms of voiding and BSF thickness with reducing printed finger width. At reverse bias, the “conventional process” shows a typical behaviour for such architecture of elevated current flow around the edges. For the “adapted process” up to -12 V, the authors demonstrate a virtually shunt-free device exhibiting reverse currents far below 1 A with no additional process step.

Decoupling the metal layer of back contact solar cells – optical and electrical benefits

We report on our work on optimising the optical and electrical properties of back contact solar cells. We use a spin coated Novolac polymer layer between metal layer and solar cell. This helps to decouple the metal optically from the solar cell and also enables the application of symmetrical metal finger widths on solar cells with thin BSF regions and large emitter regions. While the application of the polymer layer adds process steps to the cell flow it simplifies the metal contact separation, as the metal can be laser ablated from the polymer without damaging the solar cell. Further, the polymer can be inkjet patterned and used as an etch mask for a wet chemical contact opening of the underlying dielectric passivation layer.

Application of a flexible lightwand in percutaneous dilatational tracheotomy

Abstract Purpose By comparing flexible lightwand-assisted and conventional endotracheal tube (ETT) withdrawal in percutaneous dilatational tracheotomy (PDT), this paper aims to provide guidance for precise ETT withdrawal by anesthesiologists and accurate determination of the incision site by surgeons. Methods Sixty patients who underwent PDT in our hospital were randomly divided into the lightwand group (Group L, n = 30) and the withdrawal group (Group W, n = 30) using the envelope method. For Group L patients, a flexible lightwand was inserted into an ETT (based on the patient's size), the light source was positioned at the root of the cuff, and the depth from the root of the cuff to the end of the ETT was marked. The flexible lightwand was inserted into the patient's ETT to the marked depth. The ETT along with the flexible lightwand was withdrawn until the highlighted spot was located at the level of the thyroid cartilage. The incision site was approximately 3 finger widths (approximately 4.8 cm) below the highlighted spot. For Group W patients, the ETT was withdrawn to a tube depth of 17 cm at the upper incisors in males and 15 cm in females, and surgeons determined incision sites without assistance. The following metrics were recorded for the two groups: occurrences of inadvertent extubation, ETT puncture and cuff rupture; success rate of first puncture; hypoxia rate; SpO2 at the time of tracheostomy cannula intubation (T1); and postoperative hemorrhage rate. Results Inadvertent extubation, ETT puncture and cuff rupture occurred significantly less frequently in Group L than in Group W, and the success rate of first puncture and SpO2 at T1 were markedly higher in Group L than in Group W. Moreover, significant between-group differences in hypoxia rate and postoperative hemorrhage rate were observed. Conclusions The use of a flexible lightwand in PDT is a safe and effective approach. This approach can effectively and directly guide precise ETT repositioning and provide incision site confirmation with few intra- and postoperative anesthesia-related or operative complications compared with the traditional technique of ETT withdrawal to a pre-determined depth.

Laser Transfer and Firing of NiV Seed Layer for the Metallization of Silicon Heterojunction Solar Cells by Cu-Plating

We present a laser-based method for the metallization of silicon heterojunction solar cells by Cu-plating. It consists of first applying a dielectric layer on the transparent conductive oxide (TCO) as a plating mask. Then, a NiV seed is transferred by laser induced forward transfer (LIFT) from a plastic carrier foil onto the wafer. In the second laser step, the NiV layer is fired through the dielectric layer to form a contact to the TCO. After the laser process, Cu-fingers are produced by plating. The dielectric plating mask remains on the cell. Parasitic plating is prevented by using an advanced reverse pulse plating process. With the first solar cells we reach a maximum efficiency of 22.2% and an efficiency gain of 0.5%abs compared to low-temperature screen printing reference cells, due to a higher short circuit current and fill factor. The 30 μm wide fingers reach specific contact resistances down to 0.6 mΩ cm2 and also, pass a tape adhesion test. We further demonstrate that the laser process does not cause any measurable open circuit voltage loss and that a precise alignment of the two laser steps is not necessary.

Application of a flexible lightwand in percutaneous dilatational tracheotomy

PurposeBy comparing flexible lightwand-assisted and conventional endotracheal tube (ETT) withdrawal in percutaneous dilatational tracheotomy (PDT), this paper aims to provide guidance for precise ETT withdrawal by anesthesiologists and accurate determination of the incision site by surgeons. MethodsSixty patients who underwent PDT in our hospital were randomly divided into the lightwand group (Group L, n=30) and the withdrawal group (Group W, n=30) using the envelope method. For Group L patients, a flexible lightwand was inserted into an ETT (based on the patient's size), the light source was positioned at the root of the cuff, and the depth from the root of the cuff to the end of the ETT was marked. The flexible lightwand was inserted into the patient's ETT to the marked depth. The ETT along with the flexible lightwand was withdrawn until the highlighted spot was located at the level of the thyroid cartilage. The incision site was approximately 3 finger widths (approximately 4.8cm) below the highlighted spot. For Group W patients, the ETT was withdrawn to a tube depth of 17cm at the upper incisors in males and 15cm in females, and surgeons determined incision sites without assistance. The following metrics were recorded for the two groups: occurrences of inadvertent extubation, ETT puncture and cuff rupture; success rate of first puncture; hypoxia rate; SpO2 at the time of tracheostomy cannula intubation (T1); and postoperative hemorrhage rate. ResultsInadvertent extubation, ETT puncture and cuff rupture occurred significantly less frequently in Group L than in Group W, and the success rate of first puncture and SpO2 at T1 were markedly higher in Group L than in Group W. Moreover, significant between-group differences in hypoxia rate and postoperative hemorrhage rate were observed. ConclusionsThe use of a flexible lightwand in PDT is a safe and effective approach. This approach can effectively and directly guide precise ETT repositioning and provide incision site confirmation with few intra- and postoperative anesthesia-related or operative complications compared with the traditional technique of ETT withdrawal to a pre-determined depth.

Pneumatic fractures in confined granular media

We perform experiments where air is injected at a constant overpressure P_{in}, ranging from 5 to 250 kPa, into a dry granular medium confined within a horizontal linear Hele-Shaw cell. The setup allows us to explore compacted configurations by preventing decompaction at the outer boundary, i.e., the cell outlet has a semipermeable filter such that beads are stopped while air can pass. We study the emerging patterns and dynamic growth of channels in the granular media due to fluid flow, by analyzing images captured with a high speed camera (1000 images/s). We identify four qualitatively different flow regimes, depending on the imposed overpressure, ranging from no channel formation for P_{in} below 10 kPa, to large thick channels formed by erosion and fingers merging for high P_{in} around 200 kPa. The flow regimes where channels form are characterized by typical finger thickness, final depth into the medium, and growth dynamics. The shape of the finger tips during growth is studied by looking at the finger width w as function of distance d from the tip. The tip profile is found to follow w(d)∝d^{β}, where β=0.68 is a typical value for all experiments, also over time. This indicates a singularity in the curvature d^{2}d/dw^{2}∼κ∼d^{1-2β}, but not of the slope dw/dd∼d^{β-1}, i.e., more rounded tips rather than pointy cusps, as they would be for the case β>1. For increasing P_{in}, the channels generally grow faster and deeper into the medium. We show that the channel length along the flow direction has a linear growth with time initially, followed by a power-law decay of growth velocity with time as the channel approaches its final length. A closer look reveals that the initial growth velocity v_{0} is found to scale with injection pressure as v_{0}∝P_{in}^{3/2}, while at a critical time t_{c} there is a cross-over to the behavior v(t)∝t^{-α}, where α is close to 2.5 for all experiments. Finally, we explore the fractal dimension of the fully developed patterns. For example, for patterns resulting from intermediate P_{in} around 100-150 kPa, we find that the box-counting dimensions lie within the range D_{B}∈[1.53,1.62], similar to viscous fingering fractals in porous media.

Fine front side metallisation by stretching the dispensed silver paste filament with graphite nanofibres

The miniaturization of finger electrodes is an area of active research in the crystalline silicon solar cell industry, and diverse trials have been conducted with various printing techniques, including stencil, laser, aerosol jet, inkjet, electrohydrodynamic jet, and dispensing printing. Among these techniques, dispensing printing is regarded as promising due to its superior capability to construct fine finger electrodes with a high aspect ratio and homogeneity by single-pass printing without direct contact with the solar cell wafer. However, its requirements of a small nozzle, short stand-off distance between the nozzle and the solar cell, and specially formulated highly viscous silver paste with a high yield stress raise the issues of nozzle clogging, nozzle breakage by colliding with the solar cell, and the challenges of developing a dispensing printer that can accommodate high pneumatic pressures. In this study, a robust resolution of the aforementioned issues is proposed using graphite nanofibres. The small addition of graphite nanofibres to conventional silver paste greatly enhances the elongational property of silver paste. By stretching the silver paste filament with the enhanced elongational property, the diameter of the silver paste filament is reduced and a finger width of 47.7µm was achieved, which is finer by 21.4µm than the finger width achieved using paste without the graphite nanofibres. Moreover, the stable construction of finger electrodes is enabled with graphite nanofibres at a stand-off distance as far as 1mm and a printing speed as fast as 100mm/s. The resulting cell efficiency with graphite nanofibres is higher by +0.22%p (average) and +0.30%p (median) than those obtained without graphite nanofibres.

Optimization of the annealing process and nanoscale piezoelectric properties of (002) AlN thin films

In this paper, the effects of different annealing processes on the texture, surface morphology, and piezoelectric properties of aluminum nitride (AlN) thin films and the performance of AlN-based surface acoustic wave (SAW) devices were systematically investigated. Based on the crystallinity and the morphology results, it is evident that in-situ annealing method is superior to ex-situ annealing. For the AlN thin films, the crystallization and piezoelectricity were both enhanced and then receded as the annealing temperature increased from 300 to 600 °C. We demonstrated that good (002) orientation, excellent grain distribution and high relative piezoelectric coefficient of the AlN thin films were achieved via in-situ annealing at 500 °C. Meanwhile, the AlN thin films exhibited excellent polarization properties and polarization maintaining characteristics. Additionally, the uniform interdigital transducer (IDT) with 8 μm period (finger width = 2 μm) were designed and the IDT/AlN/SiO2/Si SAW devices with the center frequency f 0 of 495 MHz and insert loss of −24.1 dB were fabricated.

Theoretical comparison of the energy conversion efficiencies of electrostatic energy harvesters

The characteristics of a new type of electrostatic energy harvesting device, called an out-of-plane overlap harvester, are analyzed for the first time. This device utilizes a movable part that vibrates up and down on the surface of a wafer and a changing overlapping area between the vertical comb fingers. This operational principle enables the minimum capacitance to be close to 0 and significantly increases the energy conversion efficiency per unit volume. The characteristics of the out-of-plane overlap harvester, an in-plane gap-closing harvester, and an in-plane overlap harvester are compared in terms of the length, height, and width of the comb finger and the parasitic capacitance. The efficiency is improved as the length or the height increases and as the width or the parasitic capacitance decreases. In every case, the out-of-plane overlap harvester is able to create more energy and is, thus, preferable over other designs. It is also free from collisions between two electrodes caused by random vibration amplitudes and creates more energy from offaxis perturbations. This device, given its small feature size, is expected to provide more energy to various types of wireless electronics devices and to offer high compatibility with other integrated circuits and ease of embedment.

Characterization of Some ex situ Conserved Finger Millet (<em>Eleusine coracana</em> (L.)) Germplasm Accessions in Sri Lanka

Finger millet ( Eleusine coracana (L.) Gaertn.) is a highly nutritious and important food crop widely cultivated in the arid and semiarid regions in the world. Therefore it is worthy to be subjected to crop improvement programs. Germplasm collection and characterization are preliminary and important steps in crop improvement programmes. This study was conducted to characterize randomly selected 24 finger millet germplasm accessions conserved at the plant Genetic Resource Centre, Gannoruwa, Sri Lanka using 14 quantitative characters. The maximum positive and significant coefficient of variation was observed between weight of grain per ear and weight of sun dried ear. Phenotypic correlation between weight of grain per ear was highly significant and positively associated with days to flowering, flag leaf width, flag leaf length, plant height, culm thickness, finger length, finger width, days to maturity and weight of sun dried ears, flag leaf width, flag leaf length, plant height, culm thickness, finger length, finger width, days to maturity and weight of sun dried ears. The principal component analysis revealed that the first five component with Eigen values greater than 0.87 contributed about 85.5% of total variability. The twenty for finger millet accessions grouped in to four main clusters in the cluster analysis. Results of cluster analysis could be used in the crop breeding and conservation programmes.

CIGS cells with metallized front contact: Longer cells and higher efficiency

We have investigated the benefit of a patterned metallization on top of a transparent conductive oxide in CIGS thin-film solar panels. It was found that cells with a grid have a higher efficiency compared to cells with only a TCO. This was observed for all cell lengths used. Furthermore, metallic grids enable increase of the cell length up to 10mm virtually without reduction in efficiency. This result was obtained with a metallic grid of 20μm wide and just 1.5μm high. In addition, the following parameters were varied: TCO sheet resistance, the grid finger width and the finger height for cell lengths up to 40mm. For cell lengths of 30mm and 40mm, wider and higher fingers have improved efficiency compared to fingers of 20μm wide and 1.5μm high, which is related to a higher fill factor.