Front Transparent Conductive Oxide Research Articles

Gallium‐Doped Zinc Oxide/Tungsten‐Doped Indium Oxide Stacks with Enhanced Lateral Transport Capability for Efficient and Low‐Cost Silicon Heterojunction Solar Cells

To decrease the series resistance in front gallium‐doped zinc oxide (GZO) silicon heterojunction (SHJ) solar cells caused by high‐resistivity GZO films, stack films including tungsten‐doped indium oxide (IWO) films which have better lateral transport properties are used as the front transparent conductive oxide (TCO) to improve charge transport. The crystal structure and electrical and optical characteristics of GZO/IWO stacks with different thickness ratios are investigated, and the current–voltage performance of SHJ solar cells with front GZO/IWO stacks and rear GZO film are analyzed. The effective transmittance of the stacks is greater than 98% in the visible region. When the thickness of GZO/IWO is 50 nm:50 nm, the resistivity reaches 8.59 × 10−4 Ω cm, which is a significantly 70% reduction compared with that of a single GZO film. Meanwhile, the power conversion efficiency is improved to 23.8%, effectively reducing the efficiency gap by approximately 0.12% compared to a single IWO transparent electrode. More effective lateral transport lowers the series resistance of SHJ solar cells. By employing stacks with lower indium content in the front TCO of SHJ solar cells, the cost can be reduced without significantly affecting the efficiency, which is important for the large‐scale development of SHJ solar cells.

Power conversion efficiency of 25.26% for silicon heterojunction solar cell with transition metal element doped indium oxide transparent conductive film as front electrode

AbstractIn this paper, to improve the power conversion efficiency (Eff) of silicon heterojunction (SHJ) solar cells, we developed the indium oxide doped with transition metal elements (IMO) as front transparent conductive oxide (TCO) layer combined with microcrystalline silicon (μ‐Si:H(n+)) for SHJ solar cell. The optical and electrical properties as well as structures of hydrogenated IMO (IMO:H) films were studied and compared to conventional indium tin oxide (ITO) film. Such IMO:H films have high carrier mobility over 70 cm2/V·s, high transmittance, and low free carrier absorption, which leads to a high short circuit current density exceeding 40 mA/cm2. In addition, the low sheet resistance and contact resistivity of the IMO:H films contribute to the high fill factor of the solar cell. The average Eff of solar cells with IMO:H + μ‐Si:H(n+) is improved by 0.4% compared with that of the solar cells with ITO + a‐Si:H(n+). Finally, a certified efficiency up to 25.26% (total area, 274.5 cm2) was achieved.

Optical simulation of CsPbI3/TOPCon tandem solar cells with advanced light management

Monolithic perovskite/Si tandem solar cells (TSCs) have experienced rapid development in recent years, demonstrating its potential to exceed the Shockley–Queisser limit of single junction Si solar cells. Unlike typical organic-inorganic hybrid perovskite/silicon heterojunction TSCs, here we propose CsPbI3/TOPCon TSC, which is a promising architecture in consideration of its pleasurable thermal stability and good compatibility with current PERC production lines. The optical performance of CsPbI3/TOPCon TSCs is simulated by the combination of ray-tracing method and transfer matrix method. The light management of the CsPbI3/TOPCon TSC begins with the optimization of the surface texture on Si subcell, indicating that a bifacial inverted pyramid with a small bottom angle of rear-side enables a further minimization of the optical losses. Current matching between the subcells, as well as the parasitic absorption loss from the front transparent conductive oxide, is analyzed and discussed in detail. Finally, an optimized configuration of CsPbI3/TOPCon TSC with a 31.78% power conversion efficiency is proposed. This work provides a practical guidance for approaching high-efficiency perovskite/Si TSCs.

Optoelectrical analysis of TCO+Silicon oxide double layers at the front and rear side of silicon heterojunction solar cells

Silicon Heterojunction has become a promising technology to substitute passivated emitter and rear contact (PERC) solar cells in pursuance of lower levelized cost of electricity through high efficiency devices. While high open circuit voltages and fill factors are reached, current loss related to the front and rear contacts, such as the transparent conductive oxide (TCO) layers is still a limiting factor to come closer to the efficiency limit of silicon based solar cells. Furthermore, reducing indium consumption for the TCO has become mandatory to push silicon heterojunction technology towards a terawatt scale production due to material scarcity and costs. To address these issues dielectric layers, such as silicon dioxide or nitride cappings are implemented to reduce TCO thicknesses both diminishing parasitic absorption and material consumption. However, reducing the TCO thickness comes in cost of resistive losses. Furthermore, the TCO properties do vary with thickness and neighboring layer configuration altering the optimization frame of the device. In this paper we present a detailed analysis to quantify the optoelectrical losses trade-off associated to the TCO thickness reduction in such layer stacks. Through the analysis we show and explain why experimental bifacial cells with 20 nm front and rear TCO perform at a similar level to reference cells with 75 nm under front and rear illumination reaching efficiency close to 24% at 92% bifaciality. We present as well a simple interconnection method via screen printing metallization to implement a thin TCO/silicon dioxide/silver reflector enhancing current density from 39.6 to 40.4 mA/cm 2 without compromising resistive losses resulting in a 0.2% absolute solar cell efficiency increase from a bifacial design (23.5–23.7%). Finally, following this approach we present a certified champion cell with an efficiency of 24.6%. • Analysis of TCO variations on electron and hole contact for Si heterojunction solar cells by simulations and experiments. • Both sides 20 nm TCO + SiO 2 layer stack SHJ solar cells with 23.9% efficiency. • Champion solar cell with rear 20 nm TCO + SiO 2 layer stack and silver rear reflector with 24.6% efficiency.

Optimized front TCO and metal grid electrode for module‐integrated perovskite–silicon tandem solar cells

AbstractTo unlock the full potential of perovskite–silicon tandem solar cells with >30% efficiency at presumably low cost, the transparent conductive oxides (TCOs) and metal grid at the front side need to be adapted compared to classical silicon heterojunction (SHJ) solar cells. By means of optical and electrical modelling, we consider the main aspects to optimize the front electrode for the tandem case, where in contrast to silicon single junction devices, there are (i) different optical properties including a lower refractive index of the perovskite absorber (ii) about half the current, thus quarter the resistive power losses for the same series resistance contribution (iii) lateral transport at the front needs to be provided solely by the front TCO layer and (iv) lower thermal stability of the perovskite, which affects TCO deposition conditions and results in a less efficient sintering of the silver screen printing pastes. This study concludes that compared to silicon heterojunction cells, the thickness of the front TCO should be reduced from 75 nm to around 20 nm, resulting in less parasitic absorption and a potential cost reduction of 1.46 €ct/cell for ITO. We investigate the impact of different front metallization including plating and silver screen printing and showcase that for multi‐wire interconnection concepts, the number of wires can be reduced from 18 wires to 9 or even less depending on the front metallization. Finally, we give an outlook on the silver consumption and levelized cost of electricity.

Analysis of CdTe photovoltaic cells for ambient light energy harvesting

This paper investigates the suitability of CdTe photovoltaic cells to be used as power sources for wireless sensors located in buildings. We fabricate and test a CdTe photovoltaic cell with a transparent conducting oxide front contact that provides for high photocurrents and low series resistance at low light intensities and measures the photovoltaic response of this cell across five orders of magnitude of AM1.5G light intensity. Efficiencies of 10% and 17.1% are measured under ∼1 W m−2 AM1.5G and LED irradiance respectively, the highest values for a CdTe device under ambient lighting measured to date. We use our results to assess the potential of CdTe for internet of things devices from an optoelectronic, as well as a techno-economic perspective, considering its established manufacturing know-how, potential for low-cost, proven long-term stability and issues around the use of cadmium.

Power Losses in the Front Transparent Conductive Oxide Layer of Silicon Heterojunction Solar Cells: Design Guide for Single-Junction and Four-Terminal Tandem Applications

In silicon heterojunction solar cells, optimization of the front transparent conductive oxide (TCO) layer is required in order to minimize both electrical and optical losses. In this article, design guidelines for this overall power loss minimization are presented-extending previous TCO optimization work that was limited to the maximization of the short-circuit current density alone-and these are used to prescribe the best TCOs for both single-junction and silicon-based four-terminal tandem applications. The employed procedure determines the loss associated with the front TCO layer as a function of the TCO carrier density, mobility, and thickness, as well as the pitch between the front electrode fingers. For a representative indium tin oxide (ITO) film with a mobility of approximately 20 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ·V <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> ·s <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> and a carrier density of 2.5 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">20</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> , the loss over the 700-1200 nm infrared wavelength range-the spectrum reaching the silicon bottom cell in a typical tandem structure-is minimized by using a finger pitch of 3 mm and an ITO thickness of 100-110 nm. This compares with an optimal finger pitch of 2 mm and an optimal ITO thickness of 70 nm for the same cell operating as a single-junction device under full spectrum. The methodology presented can also readily be applied to TCO materials other than ITO, to a wide variety of specific four-terminal tandem architectures and, with minor modifications, to rear TCO layers.

Photonic-structured TCO front contacts yielding optical and electrically enhanced thin-film solar cells

Wavelength-structured transparent conductive oxide (TCO) electrodes are highly promising to improve both the optical and electrical performance of photovoltaic (PV) devices, due to wave-optical light-trapping (LT) effects and higher TCO volume without increasing optical losses.Herein we present a complete study of the benefits of microstructured IZO contacts applied on amorphous-silicon (a-Si) thin film solar cells. The IZO LT structures were integrated by an innovative colloidal lithography process on the front contact of the cells, resulting in enhancements of 26.7% in photocurrent, with respect to planar reference cells, when using an ultra-thin (30 nm) flat IZO layer between the LT structures and the a-Si absorber. However, the best efficiency enhancement (23.1%) was attained with an optimized thickness of 190 nm for this layer, due to a more favorable combination of optical and electrical gains.In view of the application of this LT strategy in flexible PV devices operating under bending, the angular response of the cells was studied for 0-90° incidence angles. This showed that the LT enhancements are generally higher at oblique incidence, reaching 53.2% and 52%, respectively in photocurrent and efficiency, at ± 70° angles with the optimized flat IZO thickness of 190 nm; and 52.2% in efficiency at ± 40° with the ultra-thin thickness of 30 nm. These results are among the highest gains reported thus far for LT-enhanced thin film solar cells.

Energy harvesting performance of bifacial and semitransparent amorphous silicon thin-film solar cells with front and rear transparent conducting oxide contacts

Bifacial and semitransparent hydrogenated amorphous silicon (a-Si:H) thin-film solar cells were prepared with front and rear transparent conducting oxide (TCO) contacts using a plasma-enhanced chemical vapor deposition process. Increased power conversion efficiencies (PCEs) and average visible transmissions (AVTs) in the visible wavelength range were realized in the cases of the bifacial and semitransparent solar cells based on the optimization of the device designs, such as front TCO contacts, intrinsic a-Si:H absorbers (i-a-Si:H), p-type hydrogenated nanocrystalline silicon carbide, and n-type hydrogenated nanocrystalline silicon layers. The dependencies of the performance parameters of the solar cells on the illumination direction and intensity were also investigated systematically. As the film thickness of the i-a-Si:H absorber layers increased from 150 nm to 450 nm, the PCEs of the solar cells respectively increased in the ranges of 6.01–7.50% and 5.25–6.25% when front and rear illuminations were used for a standard light intensity of 100 mW/cm2, while the AVTs decreased from 22.76% to 15.67% irrespective of illumination direction. The best PCEs of the bifacial and semitransparent solar cells that were fabricated with the use of optimal conditions were respectively equal to 7.94% and 6.20% when front and rear illumination conditions were used. The corresponding AVT was equal to 14.34%. The performance parameters of bifacial and semitransparent a-Si:H solar cells at varying illumination intensities in the range of 10–100 mW/cm2 were also investigated, and yielded consistent PCE values in the range of 6.39–6.62% with front illumination, and 4.95–5.15% with rear illumination.

Highly textured spray-deposited SnO2:F films with high haze for solar cells

Highly textured F-doped SnO2 (FTO) films with appropriate haze, high transparency and low resistance have been deposited on quartz glass substrates by spray pyrolysis technique at different substrate temperatures from 380 °C to 630 °C. The results show that all FTO films with pyramidal-shape grains are polycrystalline with cassiterite tetragonal structure and exhibit an obviously (200) preferred orientation. When the substrate temperature is 530 °C, the dislocation density of FTO films reaches a minimum value of 1.90 × 1015 line/m2, while the film thickness and root-mean-square roughness reach the maximum values of 613 nm and 32.3 nm, respectively. Highly textured FTO films sprayed at 530 °C exhibit the lowest turn on voltage of 1.95 eV and the optimal comprehensive optoelectrical performance with the high transmittance of 83.78%, low sheet resistance of 8.4 Ω/□ and high haze of 12.69%, which are the promising candidates as the transparent conductive oxide front electrode for film solar cells.

Efficiency Improvement of Near‐Stoichiometric CuInSe2 Solar Cells for Application in Tandem Devices

AbstractState‐of‐the‐art Cu(In,Ga)Se2 (CIGS) solar cells are grown with considerably substoichiometric Cu concentrations. The resulting defects, as well as potential improvements through increasing the Cu concentration, have been known in the field for many years. However, so far, cells with high Cu concentrations show decreased photovoltaic parameters. In this work, it is shown that RbF postdeposition treatment of CuInSe2 solar cells allows for capturing the benefits from the improved absorber quality with increasing Cu content. A reduced defect density and an increased doping level for cells with high Cu concentrations close to stoichiometry are demonstrated. Implementing a high mobility front transparent conductive oxide (TCO), the improved absorbers with 1.00 eV bandgap yield a solar cell efficiency of 19.2%, and combined with a perovskite top cell a 4‐terminal tandem efficiency of 25.0% are demonstrated, surpassing the record efficiency of both subcell technologies.

Effect of front TCO on the performance of rear-junction silicon heterojunction solar cells: Insights from simulations and experiments

In this study we make a detailed comparison between indium tin oxide (ITO), aluminum-doped zinc oxide (ZnO:Al) and hydrogenated indium oxide (IO:H) when applied on the illuminated side of rear-junction silicon heterojunction (SHJ) solar cells. ITO being the state of the art material for this application, ZnO:Al being an attractive substitute due to its cost effectiveness and IO:H being a transparent conductive oxide (TCO) with high-mobility and excellent optical properties. Through numerical simulations, the optically optimal thicknesses for a double layer anti-reflective coating system, consisting of the respective TCO and amorphous silicon oxide (a-SiO2) capping layers are defined. Through two-dimensional electrical simulations, we present a comparison between front-junction and rear-junction devices to show the behavior of series resistance (Rs) in dependence of the TCO sheet resistance (Rsh) and the device effective lifetime (τeff). The study indicates that there is a τeff dependent critical TCO Rsh value, above which, the rear-junction device will become advantageous over the front-junction design in terms of Rs. Solar cells with the respective layers are analyzed. We show that a thinner TCO optimized layer will result in a benefit in cell performance when implementing a double layer anti-reflective coating. We conclude that for a highest efficiency solar cell performance, a high mobility TCO, like IO:H, is required as the device simulations show. However, the rear-junction solar cell design permits the implementation of a lower conductive TCO in the example of the cost-effective ZnO:Al with comparable performance to the ITO, opening the possibility for substitution in mass production.

Sacrificial layer assisted front textured glass substrate with improved light management in thin film silicon solar cells

The surface morphology of the front transparent conductive oxide (TCO) films plays a vital role in amorphous silicon thin film solar cells due to their high transparency, conductivity and excellent light scattering properties. Low haze value (5.98%) and surface r.m.s roughness (3.07 nm) are the major issues of aluminium doped zinc oxide (AZO) films to be used as the front TCO due to ineffective scattering of light. Wet chemical texturization of glass substrates using aluminium doped zinc oxide (AZO) as the sacrificial layer was developed in this work to counter those issues. 45% haze and 134 nm surface r.m.s roughness were achieved in AZO coated textured glass. The etched glass/AZO samples presented a much stronger light-scattering capability than the flat glass/AZO and they showed equivalent electrical properties with flat glass/AZO. Single junction amorphous silicon solar cells were fabricated on both flat and textured AZO coated glass substrate and an increment of short circuit current of ~ 12.96% was achieved due to scattering of light from the textured substrate into the cell.

Efficient light trapping for maskless large area randomly textured glass structures with various haze ratios in silicon thin film solar cells

We report an efficient light trapping for maskless large area randomly textured glass structures with various haze ratios in silicon thin film solar cells. By well controlling the ratio of buffered hydrofluric acid (BHF) and sulfuric acid (H2SO4), we were able to prepare the randomly textured maskless glass structures with high transmittance above 90% and variable haze ratio from 20.79 to 54.78% in the visible wavelength (380–800 nm) region. It was observed that haze ratio of textured glass was dependent on feature size, etching depth and rms roughness. Multi-textured aluminum-doped zinc oxide (AZO) films were deposited on textured glass structures showed high transmittance (83.78–85.06)% and haze ratio (45.03–65.05)% in visible wavelength region. An enhancement in haze ratio of multi-textured AZO films was due to an increase of rms roughness from 16.4 to 185.5 nm as shown by 3D-alpha step profiler images. Multi-textured AZO films deposited on various textured glass superstrates were employed as a front transparent conductive oxide (TCO) layer for the fabrication of amorphous silicon (a-Si) thin film solar cells (TFSCs). The a-Si TFSCs deposited on structure-C glass showed the maximum performance as; open circuit voltage = 869 mV, short circuit current density = 16.68 mA/cm2, fill factor = 67.8% and efficiency = 9.79%. An enhancement of photocurrent was noticed from 15.64 to 16.68 mA/cm2 for as deposited a-Si TFSCs to structure-C based a-Si TFSCs.

Improved Laser Scribing of Transparent Conductive Oxide for Fabrication of Thin-Film Solar Module

Nonuniform thickness of the front transparent conductive oxide (TCO) used for fabrication of thin-film solar module (TFSM) based on micromorphic technology affects P1 laser scribing (P1 scribing on the TCO front layer). A method for improvement of the thickness uniformity of the front TCO using modification of the existing system for gas supply of the LPCVD (TCO1200) vacuum setup with the aid of gasdistributing tubes is proposed. The thickness nonuniformity of the deposition procedure is decreased from 15.2 to 11.4% to improve uniformity of the resistance of the front TCO and light-scattering factor of TFSM. In addition, the number of P1 laser scribes with inadmissible resistance of insulation (less than 2 MΩ) is decreased by a factor of 7. A decrease in the amount of melt at the P1 scribe edges leads to an increase in the TFSM shunting resistance by 56 Ω. The TFSM output power is increased by 0.4 W due to improvement of parameters of the front TCO related to application of gas-distributing tubes.

Study and development of rear‐emitter Si heterojunction solar cells and application of direct copper metallization

AbstractWe have presented a comprehensive study on the development of rear emitter silicon heterojunction (SHJ) solar cells, which shows more freedom for device optimization than the standard front emitter SHJ counterparts. The optimization of the p‐type hydrogenated amorphous silicon (a‐Si:H(p)) layer is liberated from the parasitic absorption issue, while the n‐type hydrogenated amorphous silicon (a‐Si:H(n)) layer is optimized considering the tradeoff between the light absorption loss and field‐effect passivation. The front transparent conductive oxide (TCO) layer can be designed stressing on its optical properties because the lateral transport of the majority carriers at the front side of the cell is supported by the Si substrate, while the rear TCO layer is free to be tuned for suppressing the TCO/a‐Si:H(p) contact resistance. A rear emitter SHJ solar cell (225.47 cm2) fabricated by industry compatible process has been achieved with an efficiency of over 22%. We have further demonstrated the replacement of screen‐printed silver metallization with a low cost direct copper metallization in the rear emitter SHJ solar cells. We report an exciting 22.06% cell efficiency which is comparable to that of the screen‐printed counterpart.

Using the light scattering properties of multi-textured AZO films on inverted hemisphere textured glass surface morphologies to improve the efficiency of silicon thin film solar cells

We report the light scattering characteristics of multi-textured aluminum-doped zinc oxide (AZO) thin films with high optical transmittance, haze ratio and step coverage for amorphous silicon thin film solar cells (a-Si TFSCs). Multi-textured AZO films were deposited on inverted hemisphere textured (IHT) glass surface morphologies. Multi-textured process was used to create modulated surface morphologies with micro and nano-features useful for the light scattering in visible as well as near-infrared wavelength region. Highly transparent IHT glass surface morphologies with high haze ratio were prepared by wet chemical etching of periodic glass substrates. Total transmittance of the IHT glass substrates showed higher average values (91.38–93.40%) as compared to that of bare glass (90.94%) in the visible wavelength region due to lower reflectance. Multi-textured AZO films showed higher rms roughness 100.479 nm, optical transmittance 82.60% and haze ratio 75.09% in the visible wavelength region. X-ray photoelectron spectroscopic analysis of multi-textured AZO thin films was used to study the atomic compositions and chemical binding states. Multi-textured AZO films with high transmittance and haze ratio were used as front transparent conductive oxide layers for the fabrication of a-Si TFSCs using an absorber layer thickness of 400 nm. Multi-textured AZO films deposited on the optimal textured glass surface morphologies yield the maximum performance of a-Si TFSCs as; Voc = 871 mV, Jsc = 16.55 mA/cm2, FF = 66.6% and η = 9.61%. An enhancement of photocurrent was noticed from 15.64 to 16.55 mA/cm2 for the a-Si TFSCs deposited on as deposit AZO to optimal textured AZO films.

Front and Back TCO Research Review of a-Si/c-Si Heterojunction with Intrinsic Thin Layer (HIT) Solar Cell

In this paper, we report a technical approach regarding an amorphous silicon (a-Si)/crystalline silicon (c-Si) heterojunction solar cell to solve the previous issues, and we investigate the applications of front and back transparent conductive oxides (TCOs) on this high-efficiency solar cell. The presentation of front and rear-emitter structure solar cells is included, and we investigate the TCO-material candidates for the Si heterojunction (SHJ) solar cell according to the electrical and optical properties. A high-quality TCO film is very important because it is linked to the efficiency of the c-Si-based silicon solar cell. The intention here is the applying of a high-efficiency SHJ solar cell by fabricating the high-quality TCO materials of the investigation of this study.

Si‐Doped Cu(In,Ga)Se2 Photovoltaic Devices with Energy Conversion Efficiencies Exceeding 16.5% without a Buffer Layer

AbstractIn this communication, novel and simplified structure Cu(In,Ga)Se2 (CIGS) solar cells, which nominally consist of only a CIGS photoabsorber layer sandwiched between back and front contact layers but yet demonstrate high photovoltaic efficiencies, are reported. To realize this accomplishment, Si‐doped CIGS films grown by the three‐stage coevaporation method, B‐doped ZnO transparent conductive oxide front contact layers deposited by chemical vapor deposition, and heat–light soaking treatments are used. Si‐doping of CIGS films is found to modify the film surfaces and grain boundary properties and also affect the alkali metal distribution profiles in CIGS films. These effects are expected to contribute to improvements in buffer‐free CIGS device performance. Heat–light soaking treatments, which are occasionally performed to improve conventional buffer‐based CIGS device performance, are found to be also effective in enhancing buffer‐free CIGS photovoltaic efficiencies. This result suggests that the mechanism behind the beneficial effects of heat–light soaking treatments originates from CIGS bulk issues and is independent of the buffer materials. Consequently, over 16.5% efficiencies, including an independently certified value, are demonstrated from completely buffer‐free CIGS photovoltaic devices.

Fluorine- and tin-doped indium oxide films grown by ultrasonic spray pyrolysis: Characterization and application in bifacial silicon concentrator solar cells

Multi-wire metallization and interconnection for silicon solar cells is considered as a revolutionary technology for the next generation of photovoltaic modules, since it drastically reduces their cost while boosting efficiency. In this paper, we report results obtained using an innovative approach for the fabrication of bifacial low-concentrator Ag-free Cz-Si (Czochralski silicon) solar cells based on an indium fluorine oxide (IFO)/(n+pp+)Cz-Si/indium tin oxide (ITO) structure. Transparent conducting oxide (TCO) layers, IFO and ITO, acting as antireflection electrodes, were grown by ultrasonic spray pyrolysis (USP). A copper wire contact pattern was attached by low-temperature lamination simultaneously to the front and rear TCO layers as well as to the interconnecting ribbons located outside the structure (laminated grid cell (LGCell) design). In this paper, to extend the operating range of sunlight concentration ratios of LGCells, the sheet resistance of the IFO and ITO layers has been reduced to 14 and 13Ω/sq, respectively, by increasing their thickness by about three times, from ∼85 to ∼240 nm. As a result, the operating range of the LGCells has been extended to 1–7suns. In the operating range, their front-illumination efficiency varies from 18.3 to 18.9% (back-illumination efficiency from 15.1 to 15.6%). We also report for the first time the results of systematic analysis of USP IFO properties and compare them with the USP ITO properties. The effect of the IFO thickness on grain size, electrical resistivity, charge carrier concentration and mobility, refractive index, transmission and absorption spectra, as well as optical band gap has been analyzed systematically by scanning electron microscopy, transmission and reflection spectra, optical ellipsometry and Hall measurements.