Increase In Cell Efficiency Research Articles

Influence of Aluminum Pillar Nanostructures on Thin‐Film Organic Solar Cells

This study explores the application of pillar nanostructures in organic solar cells (OSCs). The aluminum pillar nanostructures (AlPNSs) are fabricated on an active layer surface comprising of a blend poly(3‐hexylthiophene‐2,5‐diyl) and [6,6]‐phenyl C61 butyric acid methyl ester using nanoimprinting. Aluminum back electrodes are formed, resulting in AlPNSs with an imprinted pattern height of 60 ± 6 nm and a pitch of 212 ± 49 nm. Atomic force microscope images and current density versus voltage curves are obtained for the fabricated devices, both with and without AlPNSs. The results indicate a solar cell efficiency increase of 15.16% in the AlPNS OSCs compared to the reference cells. To investigate the role of AlPNSs in the enhancement, impedance spectroscopy, incident photon‐to‐current efficiency, UV–Vis reflection spectroscopy, and finite‐difference time‐domain simulations are performed for the both devices. The results demonstrate that the combination of propagating surface plasmon resonance and light‐trapping properties due to AlPNSs significantly enhances the overall optical performance. This research provides new insights into the potential of imprinted nanostructures for enhancing OSC performance, including their plasmonic and optical characteristics.

Modernizing sports an intelligent strategy for entertainment through internet of things in sports

A significant transformation towards a more engaging and entertaining viewer experience is provided by the incorporation of Internet of Things (IoT) innovation into the ever-changing world of current sports. With an emphasis on real-time tracking and assessment of athletic achievement, this study presents an extensive IoT-based strategy designed for the modern sports industry. Athlete tales, halftime displays and the general spectacle of big athletic events contribute to the entertainment value of the game. To provide a thorough assessment of athlete achievement in a timely manner, this research proposes a unique decision-making approach built on Adaptive Coral Reefs Optimized Xgboost (ACRO-XB). In particular, sport-specific characteristics are obtained through the use of electronic devices and an energy-effective procedure. To provide monitoring experts and competitors with efficient decision-making solutions, the ACRO-XB framework was developed. To validate the ACRO-XB approach, the simulation was run on a difficult dataset of 22,500 instances which is cricketers. Many modern analytical methods were used to undertake a comparison study. The simulation outcomes demonstrated that the ACRO-XB approach performed superior in conditions of recall, accuracy, f1-score and specificity by leveraging IoT data effectively for precise and timely athlete performance assessments, surpassing traditional methods in sports analytics. Furthermore, the suggested ACRO-XB approach was found to result in increased cell efficiency and stability.

Towards the fabrication of flexible thin film CdTe solar cells: The significance of substrate surfaces

Thin film CdTe solar cells have been recognized as reliable alternative for the manufacture of cheap photovoltaic solar cells of the future, due to its excellent absorber characteristics and simple, low-cost manufacturability. However, for the attainment of higher cell performances, additional studies are needed to increase cell efficiency through further development of better quality films and new fabrication processes. In the substrate-structured CdTe thin film solar cells, the CdTe absorber layer is deposited directly onto the substrate or through a back contact layer. But the quality of deposited film is believed to depend on the type and smoothness of the substrate. In this work CdTe was deposited on different substrates by RF sputtering and the effects on the deposited films were studied in terms of their structural and morphological forms. The substrates used were: pure molybdenum sheets (Mo), molybdenum-sputtered on molybdenum (Mo/Mo), molybdenum-sputtered polyimide (PI/Mo) and molybdenum-sputtered glass (glass/Mo). The characterization tools used included XRD, SEM and AFM. The results showed that all surfaces produced uniform, compact and pinhole-free films; however, those on smoother surfaces produced larger as-deposited grain sizes of up to1.7μm as against 1.3 for rougher surfaces. Non-uniformities such as overgrowth and voids were observed, but only films on PI showed evidence of cracking and peel-offs.

Effect of back opening ratio and layout design on the performance of laser ablated point contact cell

In this paper we investigate the effect of the opening ratio and the back layout design on the electrical performance of the solar cell. First, the point contact solar cells are optimized by adjusting the laser opening ratio and the virtual-to-real ratio on each grid line of back side. The experimental results show that the open-circuit voltage (Voc) of the solar cell increases as the opening ratio decreases. Analysis of the PL images also shows that the damage to the passivation layer causes the Voc to drop. By characterizing the resistance of the back line, we found that laser drilling can cause an increase in the resistance of the back line. This can also lead to the FF loss. Then, by reducing the contact area of the bus-bar at the backside, the carrier recombination of the solar cell is reduced and the Voc of the cell is increased, resulting in a 0.07% increase in cell efficiency. Finally, the simulation shows that the openings lead to an increase in the recombination current (J01) at the base of the cell, which affects the efficiency of the cell.

An integrated cooling mechanism for photovoltaic systems

Photovoltaic (PV) panels, despite their potential as a renewable energy source, suffer from performance degradation due to temperature rise. This research proposes an integrated passive cooling system that combines finned convective and radiative cooling with graphite-infused phase change material (PCM) in a cascade configuration. The cascade arrangement creates temperature stratification, delaying and restricting temperature increases. Graphite-infused PCM enhances thermal conductivity, facilitating efficient heat dissipation. Additionally, a finned heat sink augments convective heat transfer between PCM and the ambient environment, increasing the heat transfer area. A thin silica layer with pyramid lattices is incorporated to improve radiative heat transfer, particularly beneficial in hot climates with a significant temperature difference between the PV cell and the sky. A mathematical model is developed and validated against experimental data to assess the system’s performance. The model simulates PV cell temperature variations for six different scenarios to identify the most effective cooling mechanism. The study demonstrates a remarkable 27 °C reduction in peak PV cell temperature, translating to a substantial up to 100% increase in overall PV cell efficiency. This research contributes to the evolving landscape of PV cooling technologies and provides valuable insights for optimizing PV panel performance.

A study of preheating liquid desiccant and its effect on the performance of a PV/T system

When photovoltaic (PV) cells operate, their electrical efficiency decreases due to a rise in temperature. To counteract this, Photovoltaic/thermal (PV/T) systems have been created to maintain PV cell electrical performance and utilize the heat they release to warm fluids. A low temperature is required for liquid desiccant regeneration, which allows for the possibility of using the heat released by PV cells to preheat a unit prior to the main heating unit. This study investigates the use of an aluminum cold plate with a serpentine tube placed behind a PV panel to transfer heat dissipated by PV cells to a desiccant solution. Two desiccant solutions were tested: lithium chloride (LiCl) and potassium formate (KCOOH). Using COMSOL Multiphysics, three-dimensional CFD simulations were conducted to analyze the temperature of both the photovoltaic cells and the solution exiting the cold plate. The simulation results were then used to determine the hybrid system's electrical, thermal, and overall efficiencies. Under nominal operating cell temperature (NOCT) conditions, the total efficiency of the hybrid system was 57.15 % and 55.28 % when using LiCl and KCOOH solutions, respectively, with a cold plate inlet temperature of 25 °C and a mass flow rate of 30 g.s-1. Given the similar efficiency of the system and the lower corrosiveness and cost of KCOOH solution compared to LiCl solution, the study concluded that using KCOOH solution is more appropriate. Simulations were conducted under NOCT conditions to compare the system's performance using desiccant solution and water. As expected, the thermodynamic properties of water resulted in a greater decrease in temperature and increased cell efficiency, but using the desiccant solution directly in the cold plate for cooling eliminated the need for an additional heat exchanger in the system.

Investigation of the effect of dye sensitized solar cell efficiency of donor and anchor groups in phthalocyanine compounds

In order to obtain higher power conversion performance in dye-sensitized solar cells, phthalocyanine compounds (ZnPc-1 and ZnPc-2) containing electron donor methoxy groups and aldehyde groups as anchors were synthesized in this study. The photovoltaic and electrochemical properties of these compounds were studied and their applicability as photosensitizers in DSSCs was investigated. The photovoltaic cell efficiencies (PCE) of the devices were in the range of 0.43–0.76 % under simulated AM 1.5 solar irradiation of 100 mW/cm2. Considering the photovoltaic performance of the produced DSSC devices, the anchor group and the chelate effect, it was observed that the efficiency increased, respectively, ZnPc-1 < ZnPc-2. The highest PCE value of 0.76 % was obtained with asymmetric ZnPc-2 based DSSC under. It has been explained that methoxy groups are electron donors and contribute to intramolecular electron mobility and that better electron transfer with single aldehyde anchor increases cell efficiency. In addition, the increase in the number of methoxy groups with known donor properties on the molecule also contributed to the increase in cell efficiency by increasing electron transfer. All compounds synthesized were characterized using FTIR, UV-vis and MS spectroscopic data.

Numerical analysis of the relation between the porosity of the fuel electrode support and functional layer, and performance of solid oxide fuel cells using computational fluid dynamics

The development of the hydrogen industry brings new technological challenges. Solid oxide fuel cells (SOFCs) seem to be one of the leading devices for hydrogen conversion and its production while operating in its reverse mode (as an electrolyser). Fine-tuning of SOFC microstructure might extend cells life and boost their performance. The article presents original numerical studies of the performance of solid oxide fuel cells, based on the OpenFuelCell model, extended by fuel and oxidant concentration loss equations. Transport phenomena in the porous structure of the anode functional layer (AFL) and the anode support layer (ASL) were simulated using the modified Fick's law (MFL) and the Knudsen diffusion coefficient. The presented research focuses on the influence of fuel distribution in fuel electrode of SOFC together with reacting zones and on the influence of AFL and ASL microstructure characteristics on cell performance. The studies included porosity in the range of 30%–60% for both types of anode layers. The obtained results showed a significant impact of the porosity characteristics on the SOFC performance and indicated the possible direction for further improvement. Numerical studies have shown that an increase in anode layers porosity of 30% allows for an increase in cell efficiency of even 15%. Experimental, as well as numerical results, showed that above a porosity of 49%, further increasing the porosity has no strong effect on the results. Also, a novelty in the work and an important part of it is the comparison of the impact of microstructure manipulation of the two anodic layers. Improvement of ASL microstructure allows to better, more homogeneous, fuel distribution inside the anode. Additionally, it increases the concentration of the fuel in the functional layer by up to 8%, which leads to increase in SOFC performance.

Performance evaluation of PV panels for green HHO gas generation: Energy, exergy, and economic investigation

The paper aim is to design and fabricate of solar-powered alkaline water electrolyzer to produce hydroxy gas (HHO) flow with enhanced efficiency. Oxyhydrogen gas was yielded by the electrolysis of water utilizing various NaOH concentrations of 5, 10, 15 and 20%. Based on the solar radiation peak time at 12:00 p.m., the increase of solar intensity from 502 W/m2 to 1000 W/m2 (from 08:00 AM to 12:00 PM) led to the current and voltage increases by about 700% and 450%, respectively. Cell efficiency increase was from 61% to 69% by about 13% increase ratio. The output of HHO increases with cell gap between 1 and 3 mm. For temperatures between 30 °C and 60 °C, HHO generation declines at the gaps of cells between 4 and 7 mm. At the same operating temperature, the cells gap of 1, 3, 4, and 7 mm produced flow rates of 928, 975, 960, and 925 ml/min, respectively. After 30 min, the rate of HHO achieves the maximum values of 866, 985, 1090, and 1140 ml/min at NaOH concentrations of 5, 10, 15, and 20%. The simplicity, ease of assembly, and manufacture of the dry cell made it appealing. The HHO dry cell is affordable, made from readily available components, and adaptable to engines that receive their power from solar panels. The cost per liter to produce HHO varies between 0.437 and 0.575 $.

A numerical investigation of a photovoltaic thermal system contained a trapezoidal channel with transport of silver and titanium oxide using the water as base fluids

This article presents a numerical investigation of forced convection in a PV/T system to reduce the temperature caused by solar radiation, which can decrease its electrical energy production. The study uses two types of nanoparticles, namely titanium oxide and silver, combined with water as the base fluid. The PV/T system features a trapezoidal flow channel, and the Navier-Stokes and energy equations are solved using the COMSOL Multiphysics 6.0 finite element-based computer code to obtain an approximate solution. The study tests the range of Reynolds number, aspect ratio, and the volume fraction of both nanoparticles as (100–1000), (0.4–1), and (0.01–0.25), respectively, to analyze the various impacts of the selected variables on the percentage change in cell temperature and efficiency by varying the Reynolds number and aspect ratio between the inlet to the outlet height of the flow channel. The results indicate that increasing the Reynolds number from 100 to 1000 can reduce cell temperature by 50% and increase cell efficiency by 4.4%. Similarly, changing the aspect ratio from 0.4 to 1 can reduce the percentage temperature of the cell due to inlet temperature by 26.2% and increase cell efficiency by 1.6%. The study reveals that increasing the outlet height while fixing the outlet height of the channel can improve cell performance. Additionally, increasing the volume fraction of both nanoparticles in the base fluid can enhance the cell efficiency of the PV/T system.

Shedding light on electronically doped perovskites

Halide perovskites solar cells (PSCs) are making true on past promises, having reached power conversion efficiencies (PCEs) of 25.7% and long lifespans (>3000 h). Although stability has become the focus of research efforts, a significant number of researchers are still dedicated to further increasing cell efficiency. To push PCE any higher however, every element of the solar cell must be controlled and optimized. In the context of the recent advancements in halide perovskite doping, we analyse how and why doping can modify the PCE of PSCs. We find that optimal doping levels are highly dependent on carrier mobilities and device architecture, namely whether the hole- or electron-transport layer are on the front-side (illumination-side) of the device. More precisely, there are four regimes defined by carrier mobilities in which different physical processes are more, or less, important causing a change to the optimal doping level. When electron and hole mobilities are comparable, and diffusion lengths are not at least an order of magnitude larger than the perovskite film thickness, devices with the electron-transport layer on the front side (n-i-p) perform better with a p-doped perovskite, whereas devices with the hole-transport layer on the front side (p-i-n) perform better with an n-doped perovskite. The existence of these four regimes is especially pronounced for PSCs due to the very high absorption coefficients and rather low carrier mobilities in halide perovskites. We model the solar cell by employing a drift-diffusion simulation in SCAPS (a Solar Cell Capacitance Simulator) to provide a full rationale for the phenomenon and analyse the conditions under which this effect is significant. The findings presented here are based on the perovskite properties measured by multiple groups and are directed predominantly towards experimentalists working with devices.

Arsenic doping and diffusion in CdTe: a DFT study of bulk and grain boundaries

The doping of CdTe with As is a method which is thought to increase cell efficiency by increasing electron hole concentrations. This doping relies on the diffusion of As through CdTe resulting in AsTe substitution. The potential effectiveness of this is considered through kinetic and electronic properties calculations in both bulk and Σ3 and Σ9 grain boundaries using Density Functional Theory. In bulk zinc-blende CdTe, isolated As diffuses with barriers <0.5 eV and with similar barriers through wurtzite structured CdTe, generated by stacking faults, suggesting that As will not be trapped at the stacking faults and hence the transport of isolated As will be unhindered in bulk CdTe. Substitutional arsenic in bulk CdTe has little effect on the band gap except when it is positively charged in the AX-centre position or occurring as a di-interstitial. However in contrast to the case of chlorine, arsenic present in the grain boundaries introduces defect states into the band gap. This suggests that a doping strategy whereby the grain boundaries are first saturated with chlorine, before single arsenic atoms are introduced, might be more beneficial.

Sputtering Pt on Low-Loading Iridium-Based Anode to Improve Both Cell Performance and Gas Permeation Issue in PEM Water Electrolysis

Polymer electrolyte membrane (PEM) water electrolysis is one of the most promising technologies which can integrate with renewable sources to produce sustainable hydrogen energy. Thin membranes were preferred for making membrane electrode assembly (MEA) for the PEM electrolyzer to increase cell efficiency. However, these membranes suffered from significant gas permeation consequently resulting in an explosion by the combination of hydrogen and oxygen, especially in the high-pressure operation. Many publications employed platinum as a recombination catalyst for reducing hydrogen concentration in the oxygen product stream to ensure safe operation [1-4]. Beside, Pt could be coated on oxidated Ti porous transport layer (PTL) to improve contact resistance between Iridium-based electrode and PTL [5]. In this work, a thin layer of platinum was sputtered on the surface of a low-loading anode (0.5 mgIr/cm2). Three MEAs prepared from commercial hydrous IrOx catalyst with 3 different loadings (1 mgIr/cm2, 2 mgIr/cm2and 3 mgIr/cm2) were used as reference. SEM images of Pt-sputtered MEA showed that the Pt layer had a thickness of approximately 80 nm corresponding to a loading of 0.4 mgPt/cm2. The electrochemical performance of Pt-sputtered MEA was significantly higher than that of bare MEA with 1 and 2 mgIr/cm2. The better performance of MEA with the presence of Pt is due to the improvement in contact resistance between the catalyst layer and PTL, in which lower HFR can be seen. In addition, its performance was comparable to high-loading MEA, while the total amount of precious metal was much lower (0.9 and 3 mg/cm2, respectively). The sputtered MEA also exhibited a slight difference in kinetic resistance compared to pristine MEA. On the other hand, the MEA with the addition of Pt shows a lower concentration of hydrogen in the oxygen product stream compared to pristine MEA at ambient pressure.[1] C. Klose et al., "Membrane interlayer with Pt recombination particles for reduction of the anodic hydrogen content in PEM water electrolysis," Journal of The Electrochemical Society, vol. 165, no. 16, p. F1271, 2018.[2] N. Briguglio, F. Pantò, S. Siracusano, and A. Aricò, "Enhanced performance of a PtCo recombination catalyst for reducing the H2 concentration in the O2 stream of a PEM electrolysis cell in the presence of a thin membrane and a high differential pressure," Electrochimica Acta, vol. 344, p. 136153, 2020.[3] S. Garbe, E. Samulesson, T. J. Schmidt, and L. Gubler, "Comparison of Pt-Doped Membranes for Gas Crossover Suppression in Polymer Electrolyte Water Electrolysis," Journal of The Electrochemical Society, vol. 168, no. 10, p. 104502, 2021.[4] A. Stähler, M. Stähler, F. Scheepers, W. Lehnert, and M. Carmo, "Scalable Implementation of Recombination Catalyst Layers to Mitigate Gas Crossover in PEM Water Electrolyzers," Journal of The Electrochemical Society, vol. 169, no. 3, p. 034522, 2022.[5] M. Bernt et al., "Effect of the IrOx Conductivity on the Anode Electrode/Porous Transport Layer Interfacial Resistance in PEM Water Electrolyzers," Journal of The Electrochemical Society, vol. 168, no. 8, p. 084513, 2021. Figure 1

Enhancement of multijunction solar cell efficiency using a cover layer of Eu3+, Tb3+ and Eu3+/Tb3+ doped GeO2-PbO-Al2O3 glasses as spectral converter of solar radiation

The present study reports the multijunction solar cell efficiency enhancement using a cover layer of GeO2-PbO-Al2O3 glasses single doped with Eu3+ and Tb3+ (with and without Ag nanoparticles (NPs)) and codoped with both of them. We highlight that Al2O3 is a network modifier that promotes the occupation of rare-earth ions in more asymmetric sites, and the change in the coordination environment improves the luminescence that benefits the solar cell efficiency. The influence of the downconversion process and the energy transfer mechanisms between Tb3+ and Eu3+ ions are investigated using different concentrations of Eu2O3 and Tb4O7 in single and codoped samples. Moreover, the plasmonic effects of Ag NPs on the solar cell efficiency increase are also studied and compared with those promoted by different doping concentration to reach the best condition for the multijunction solar cell performance. However, in all cases, it is the contribution of the highest luminescence and considerable transmittance that led to the solar cell best performance. The sample single doped with Eu2O3 promoted an increase of 14%; on the other hand, an increase of 13% was observed for the glass doped with Tb4O7 and with 0.5% of AgNO3. For the case of the codoped samples, solar cell efficiency increase of 10% was reached when the largest Eu2O3 concentration was used.

Impact of Al on ZnO Electron Transport Layer in Perovskite Solar Cells

Perovskite solar cells have shown remarkable performance and improvements in terms of solar cell efficiency. The ETL material is one of the important components in perovskite solar cells in conducting electrons to produce current. Here, ZnO was used as ETL material in a perovskite solar cell using the SCAPS 1D simulation software. The ZnO ETL showed poor cell efficiency due to its reaction with the perovskite material. A small amount of Al doped into ZnO was introduced to enhance the physiochemical properties of the ZnO against perovskite materials. Al concentrations were varied between 1 and 4 mol% to observe the effect on cell efficiency. Compared with a conventional ZnO ETL solar cell with 0 mol% Al perovskite, the Al-doped based solar cell showed better performance. Meanwhile, perovskite solar cells with 1 mol% Al-doping and appropriate layer thickness showed the best cell performance in improving the charge transport mechanism, resulting in increased cell efficiency. Thus, the parameters studied can be a guide in the fabrication process.

Advanced supercritical fluid technique to reduce amorphous silicon defects in heterojunction solar cells

The advanced supercritical fluid (SCF) technique was applied to reduce defects in the amorphous silicon thin-film layer and enhance the efficiency of a heterojunction (HJT) solar cell from 18.1% to 19.6%. An amorphous silicon thin-film layer has been used as a passivation layer between the substrate and electrode contact in HJT solar cells; however, many dangling bonds exist in the amorphous silicon thin-film layer. Therefore, the SCF technique was developed to passivate defects. The advantage of a supercritical state is high penetrability and low temperature. Thus, this SCF treatment can passivate defects in the completed device without changing the original fabrication process. After treatment, the passivation of dangling bonds was examined using Fourier-transform infrared spectroscopy, which confirmed the improved Si–H bonding. Moreover, electrical properties such as open-circuit voltage, short-circuit density, efficiency, shunt resistance, and leakage current were measured to confirm the enhancement. A simulated light source of 1 kW M−2 global AM1.5 spectrum was used to analyze the increase in cell efficiency, and the dark current was analyzed to confirm the leakage current improvement. Finally, a model for explaining the phenomenon in cells after treatment was developed.

Optical analysis of light management for finger designs in CPV systems

AbstractConcentrated photovoltaic (CPV) systems can achieve high energy conversion efficiencies due to their use of concentrating optics and highly efficient solar cells; however, power losses arising from the front surface reflection and metallization shading typically contribute a significant fraction to the total power loss for these devices. In flat silicon photovoltaic (PV) modules, the front‐metal finger shape is often shaped to minimize shading losses. Finger shape is even more relevant for CPV cells where the current density and front metal shading are much higher. This study compares the optical performance of five light management finger designs in CPV systems with two different refractive homogenizers. The optical efficiency and loss analysis were determined using ray‐tracing simulations. It is shown that shaped, light diverting metal fingers can improve the optical efficiency in CPV systems by up to 9.9% absolute compared to rectangular fingers, corresponding to an absolute cell efficiency increase of 3.0%. Although sharp edged triangular finger structures may be challenging to fabricate, significant optical gains can still be achieved with trapezoid or rounded cap finger shapes.

Exergy efficiency optimization of photovoltaic and solar collectors’ area in buildings with different heating systems

Exergy as a measure of useful work can be used in the design, simulation and performance evaluation of different energy systems. In this paper it is investigated the Serbian residential building with photovoltaics and solar collectors on the roof, and with three different heating systems: electrical heating, district heating and central heating with gas boiler. Exergy optimization was performed with the aim to determine the optimal area of the PV array and solar collectors on the roof (including embodied exergy). With these values, the maximum exergy efficiency of installed solar systems is obtained, and building primary energy consumption is minimized. The residential buildings with variable temperature in domestic hot water system, variable PV cell efficiency and variable hot water consumption are investigated in order to achieve positive-net energy building. The buildings were simulated in EnergyPlus software and Genopt was used for software execution control during optimization. The obtained results show that positive-net energy building with optimally sized photovoltaics and solar collectors’, can be achieved in a case of gas heating system, and in the cases of PV cell efficiency of 14% and 16%. Also, an environmental and economic analysis of the most favourable solutions from exergetic optimization was performed. Total CO2 emission (with embedded emissions of CO2) increases with increasing amount of generated energy – for PV system of cell efficiency of 12%, 14% and 16%, total CO2 emission of solar systems is 20.8 kg CO2/m2, 23.5 kg CO2/m2 and 26.2 kg CO2/m2, respectively. The emission payback time decreases with increasing PV cell efficiency from 1.11 to 1.04 years. With the increase of PV cell efficiency, there is an increase in the annual financial profit (from 1518 to 4305 €), while at the same time, the investment payback period decreases (from 16.9 to 6.1 years). Best results are obtained for the building with gas heating system.

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.

Simulation approach of new photovoltaic structures based on epitaxial silicon thin layers on a monocrystalline silicon substrate

In the photovoltaic field, research is focused on two important axes: increasing cell efficiency, and reducing fabrication costs. To reduce the cost of the base materials, it is necessary to reduce the thickness of the active layers. The basic idea is to make a layer of high structural and electronic quality silicon of small thickness (10–50 μm). This layer could be grown by epitaxial techniques on a low-cost monocrystalline silicon substrate with an emitter formed by phosphorus diffusion. The silicon layer is characterized by a diffusion length comparable to its thickness, a value that can be expected for the epitaxial layers. This study aims to optimize the physical and technological performances of a crystalline silicon solar cell deposited by an epitaxial process on a low-cost monocrystalline silicon substrate with large thicknesses since there is no reflector on the backside. This structure is characterized by the following parameters: (Thickness of the base layer XB = 56 μm, the efficiency η = 15.2%, the open-circuit voltage Voc = 623 mV and the short-circuit current Isc = 30 mA). The calculations were carried out by the PC1D software, aiming to find a new solar cell structure by keeping the same characteristic parameters mentioned above (η, Isc, and Voc) while decreasing the thickness of this solar cell. The effect of the different parameters on the performance of the solar cell was investigated. The obtained results showed that it is possible to reduce the substrate thickness from 56 to 30 μm while keeping the same characteristics parameters of the cell (η = 15.2%, Voc = 622.7 mV, Isc = 30.1 mA).