Heterojunction Technology Research Articles

2D semiconductor Van Der Waals heterojunction applications

As the demand for new energy sources continues to grow, the market value of solar power, a key component of new energy, is also expanding. Van der Waals (vdW) heterojunctions made from two-dimensional (2D) semiconductors especially transition metal dichalcogenide (TMD), demonstrates immense potential in terms of the portability and efficiency of photovoltaic devices. Additionally, it shows great promise in the field of novel miniature high-speed photoelectric detectors. It offers multiple benefits, including high carrier mobility, tunable optical and electrical properties, enhanced optical properties and ultra-thinness, making it suitable for variant applications. This report reviewed the emerging 2D semiconductor Vdw heterojunction technologies on photodetection and photovoltaics. Summarized the advantages of MoS2/WSe2, WSe2/ReS2 and WSe2/WS2-based Vdw heterojunctions and their challenges. The continued research and development in this field are expected to lead to more efficient energy conversion, scalable fabrication methods, and broader commercial applications of these technologies.

Comparative experiment on the efficiency of water cooling in photovoltaic modules in the climatic conditions of Southern Russia

The problems of ensuring the safety of operation of nuclear power plants are always paid increased attention. In addition to the self-contained diesel generator sets used to maintain the operation of safety systems in case of loss of external power supply, it is also advisable to consider the use of more environmentally friendly self-contained photovoltaic units at this stage. The work is aimed at a comparative experimental study of the efficiency of water cooling in real natural climatic conditions of Southern Russia. In this experiment, cooled and uncooled photovoltaic modules are simultaneously exposed to a complex of variable weather factors: solar radiation, cloudiness, wind, pressure, temperature and humidity of the environment. Both modules have loads connected via MPPT controllers. The effect of water cooling on the energy efficiency of photovoltaic modules assembled from silicon heterojunction technology (HJT) solar cells was studied. The solar panels were made from 130 micron thick HJT cells interconnected using SmartWire contact technology. It reduces power loss due to possible defects such as cracks. The conditions for ensuring the highest degree of similarity between the parameters of the cooled and uncooled modules have been met. A comparative experimental study was conducted in Astrakhan State University using a long-term monitoring system for the characteristics of photovoltaic modules. This is a test photovoltaic system (TPS), built on the basis of the Paragraph PL2 electronic recorder. A significant increase in module output when working with cooling was established. At insolation of 987.5 W/m2, the power generated by the cooled module was 93.0297 W, while the power of the module without cooling was 79.306 W. The difference comprised 13.7237 watts. Power increased by 17%. In the experiment, the average efficiency value when the module was cooled was 0.15977. When uncooled, it was 0.13764. The efficiency intensified by 2.21%. This increase is significant. The results obtained confirm the fairly high efficiency of water cooling in photovoltaic modules in real natural operating conditions for regions with high ambient temperatures, Southern Russia, in particular

Modelling the use of PVSYST software for a stand-alone PV solar system "off grid" with batteries by utilizing silicon hetero-junction technology (HJT) panels in Iraq/Basra.

Fossil fuels have been widely used in electricity generation in recent years, resulting in excessive CO2 emissions. Continuing this would increase the temperature of the atmosphere, causing storms, hurricanes, droughts, dust storms, and flooding. Due to the fact that renewable energy produces few or no emissions, it has become increasingly important for it to be adapted in recent years. During the past few years, the PV sector has experienced rapid growth. New technology has enabled PV cells to become more efficient, and the sector is rapidly embracing new technologies. In this regard Silicon Hetero-junction technology HJT has been able to offer additional benefits: It is able to achieve efficiency levels above 24% at temperature 20C°. HJT solar panels have over 90% module bifaciallity and a low temperature coefficient (-0.24%/°C), which benefits to the levelized cost of energy (LCOE) and output power for PV systems. The objective of this study is to assess and compare the efficiency of high-quality (HJT) solar panels and SI-MONO solar panels for a residential off-grid system with at a peak power of 3 kWh and a daily power close to 20 kWh with a 48V system in Iraq/Basra. In order to calculate energy output, and enhance the system design, PVSYST (7.2.11 version) software was used. PVSYST's database contains meteorological data, including characteristics, solar radiation, and ambient temperature.

Performance and durability of electrically conductive tape for shingled Si heterojunction technology cells

AbstractElectrically conductive tape (ECT) was characterized and used to assemble shingled cell strings at low temperature to achieve high reliability Pb‐ and Ag‐free interconnections. The volume resistivity for two considered ECTs are 0.13 ± 0.06 mΩ·cm and 0.47 ± 0.20 mΩ·cm and specific contact resistances, 6.85± 2.00 mΩ·cm2 and 6.30 ± 0.37 mΩ·cm2 using the emerging IEC 62788‐8‐1 Technical Specification for assessment of electrically conductive adhesives (ECA). Durability and performance of the technology in glass–glass mini modules were evaluated with temperature cycling, damp heat testing, and combined‐accelerated stress testing (CAST). Through temperature cycling (−40°C to 85°C) applying five times the mini module short‐circuit current in forward bias and in the multi climate CAST protocol, there was negligible degradation of fill factor after replacing connectors at the modules' cable leads; however, CAST resulted in short circuit current loss attributed to degradation in light collection by the cells, not the ECT. The IEC 61215‐2 85°C, 85% relative humidity damp heat testing showed susceptibility of the HJT cells to effects of humidity in the electroluminescence intensity around the module perimeter that degraded power performance by 4% (relative). Contrasting the IEC 61215‐2 qualification testing‐based damp heat testing with CAST, factors such as the optical stress of CAST may precipitate the degradation of the modules whereas the humidity levels and duration of IEC 61215‐2 damp heat testing may lead to excessive levels of humidity diffused into the modules, potentially resulting in degradation that is unrepresentative of the field.

Analysis of SiC/Si Heterojunction Band Energy and Interface State Characteristics for SiC/Si VDMOS.

SiC/Si and GaN/Si heterojunction technology has been widely used in power semiconductor devices, and SiC/Si VDMOS and GaN/Si VDMOS were proposed in our previous paper. Based on existing research, breakdown point transfer technology (BPT) was used to optimize SiC/Si VDMOS. Simulation results showed that the BV of the SiC/Si heterojunction VDMOS was considerably increased from 259 V to 1144 V, and Ron,sp decreased from 18.2 mΩ·cm2 to 6.03 mΩ·cm2 compared with Si VDMOS. In order to analyze the characteristics of the SiC/Si heterojunction structure deeply, the influence of the interface state characteristics of the SiC/Si heterojunction on the electrical parameters of VDMOS was analyzed, including electric field characteristics, blocking characteristics, output characteristics, and transfer characteristics. In addition, the influence of the interface state of the SiC/Si heterojunction on energy band characteristics was analyzed. The results showed that with an increase in the interfacial charge (acceptor) concentration, the p-type trap layer was introduced into the interface of the SiC/Si heterojunction, energy increased slightly, and the barrier height difference at the heterojunction increased, resulting in an increase in BV. At the same time, since the barrier height became higher, electrons did not flow easily, so Ron,sp increased. On the contrary, when a charge (donor) was introduced at the interface of the SiC/Si heterojunction, the number of electrons in the channel increased, resulting in an increase in the electron current, which is conducive to the flow of electrons, resulting in a decrease in Ron,sp. The energy band and other characteristics of devices with temperature were simulated at different temperatures. Finally, the effects of SiC/Si heterojunction interface states on interface capacitances and switching performances of VDMOS devices were also discussed.

Four failure modes in silicon heterojunction glass-backsheet modules

Silicon heterojunction technology (HJT) is expected to gain a significant market share in the near future. For HJT to deliver a low levelized cost of electricity (LCOE), it needs to have a high initial efficiency and degrade less than 0.5% relative per year. This work investigates damp heat-induced failure modes in silicon HJT glass-backsheet modules. Four unique failure modes are identified after damp heat (DH) testing: point failure (Type-1); failure around the interconnected regions of the busbars and ribbon wires (Type-2); failure between the busbars (Type-3); and failure at/on the interconnected regions of busbars and ribbon wires (Type-4). The Type-1 failure mode is likely caused by a chemical reaction between surface contaminants (introduced to the cells during handling or characterization before encapsulation) and moisture that increase charge carrier recombination and lead to a loss in maximum power (Pmax) of up to 40%rel in this study. Type-2 and Type-3 failure modes cause Pmax losses of ∼5%rel and 50%rel, respectively, in this study and can appear due to exposure to soldering flux used for connecting the ribbon wires and busbars. Finally, the Type-4 failure mode causes a Pmax loss of ∼16%rel in this study after the DH test. The evidence suggests that this failure mode is likely due to the interaction of acetic acid, generated from a reaction between the encapsulation material and moisture, ribbon wires, and silver paste (busbars), resulting in recombination loss. We believe these failure modes must be well understood and mitigated at preferably the solar cell level to ensure that HJT can meet its LCOE potential.

Study of Microstructure and Mechanical Properties of Electrodeposited Cu on Silicon Heterojunction Solar Cells

This study investigated the use of a pure copper seed layer to improve the adhesion strength and reduce the residual stress of electroplated copper films for heterojunction technology in crystalline solar cells. The experiment involved depositing a copper seed layer and an indium tin oxide (ITO) layer on textured silicon using sputtering. This resulted in the formation of a Cu(s)/ITO/Si structure. Following this step, a 10 µm thick copper layer was electroplated onto the Cu(s)/ITO/Si structure. Various characterization techniques were employed to evaluate the electroplated copper films’ microstructures, residual stress, and adhesion strength. The microstructures of the films were examined using a scanning transmission electron microscope (STEM), revealing a twin structure with a grain size of approximately 1 µm. The residual stresses of the as-deposited and annealed samples were measured using an X-ray diffractometer (XRD), yielding values of 76.4 MPa and 49.1 MPa, respectively. The as-deposited sample exhibited higher tension compared to the annealed sample. To assess the adhesion strength of the electroplated copper films, peel-off tests were conducted at a 90° angle with a constant speed of 30 mm/min. The peel force, measured in units of N/mm, was similar for both the as-deposited and annealed samples. Specifically, the peel force for electroplating copper on the copper seed layer on the ITO was determined to be 2.6 N/mm for the maximum value and 2.25 N/mm for the average value. This study demonstrated that using a pure copper seed layer during electroplating can improve adhesion strength and reduce residual stress in copper films for heterojunction technology in crystalline solar cells. These findings contribute to the development of more reliable and efficient solar-cell-manufacturing processes.

Prediction of sub-pyramid texturing as the next step towards high efficiency silicon heterojunction solar cells

The interfacial morphology of crystalline silicon/hydrogenated amorphous silicon (c-Si/a-Si:H) is a key success factor to approach the theoretical efficiency of Si-based solar cells, especially Si heterojunction technology. The unexpected crystalline silicon epitaxial growth and interfacial nanotwins formation remain a challenging issue for silicon heterojunction technology. Here, we design a hybrid interface by tuning pyramid apex-angle to improve c-Si/a-Si:H interfacial morphology in silicon solar cells. The pyramid apex-angle (slightly smaller than 70.53°) consists of hybrid (111)0.9/(011)0.1 c-Si planes, rather than pure (111) planes in conventional texture pyramid. Employing microsecond-long low-temperature (500 K) molecular dynamic simulations, the hybrid (111)/(011) plane prevents from both c-Si epitaxial growth and nanotwin formation. More importantly, given there is not any additional industrial preparation process, the hybrid c-Si plane could improve c-Si/a-Si:H interfacial morphology for a-Si passivated contacts technique, and wide-applied for all silicon-based solar cells as well.

Transfer-Length Method Measurements Under Variable Illumination to Investigate Hole- Selective Passivating Contacts on c-Si(p) and c-Si(n) Wafers

In this article, transfer length method (TLM) measurements under variable illumination are applied to study p-type carrier selective passivating contacts (CSPCs) employed in the silicon heterojunction (SHJ) technology. In the case of p-type CSPCs deposited on p-type crystalline silicon (c-Si(p)) wafers, we demonstrate that illumination has a strong impact on the contact resistivity ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\rho _{c}$</tex-math></inline-formula> ) value, as demonstrated in our previous contribution in the case of n-type CSPCs on c-Si(n). Noticeably, it was again found that <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\rho _{c}$</tex-math></inline-formula> increases and that the c-Si sheet resistance ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$R_\text{sh}$</tex-math></inline-formula> ) decreases with the illumination. In addition, we demonstrate that <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\rho _{c}$</tex-math></inline-formula> is impacted differently by illumination depending on the doping of the p-type thin hydrogenated silicon layer. Then, we investigate and discuss the applicability of TLM measurements under illumination to measure p-type CSPCs deposited on their inverse type c-Si(n) wafers. First, performing TLM measurement in dark conditions of such samples allow one to measure <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$R_\text{sh}$</tex-math></inline-formula> values with orders of magnitude corresponding to the c-Si(n) inversion layer one. Second, we demonstrate that under illumination, the lateral transport inside the c-Si(n) bulk is supported by the electrons thanks to two experimental evidences, i.e., that the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$R_\text{sh}$</tex-math></inline-formula> behavior as a function of injection behaves as the one of electrons and that an electron transport inside the c-Si(n) wafer in the presence of two p-type CSPCs TLM pads can only be mediated thanks to photogeneration under one pad and recombination under the other. These results provide additional understandings of the TLM measurement under illumination as well as strong insights for the investigation of carriers' transport and electrical losses in CSPCs solar cells.

Ternary heterostructures of GO, MoS[formula omitted], and g-C[formula omitted]: Synthesis, stability and properties

The development of heterojunction technology with exceptional capabilities has emerged as an auspicious approach for both environmental remediation and improved performance in electronic devices. Present study reports two different heterostructures composed of graphitic carbon nitride (g-C3N4), molybdenum disulfide (MoS2), and graphene oxide (GO) i.e., GO/g-C3N4/MoS2 (H1) and GO/MoS2/g-C3N4 (H2). The heterostructure anticipated by quantum modeling was synthesized by facile ultra-sonication method and characterized via Powder XRD, FT-IR, and FE-SEM spectroscopic techniques. The finding indicates that the optimized GO/g-C3N4/MoS2 heterostructures exhibit a energy gap of 1.12 eV whereas, GO/MoS2/g-C3N4 heterostructure is conducting material. The periodic energy decomposition analysis reveals that heterostructure H1 is energetically more favorable than that of H2. The absorption coefficient, reflectance, and refractive index showed red shifts in both the heterostructures, while a blueshift was observed in the energy loss spectrum. The outcome of both theoretical and experimental observations highlights that the resultant heterostructure closely resemble with the theoretically predicted H1. The novel heterostructure anticipated here stands the test of meticulous theoretical and experimental examinations to establish its proficiency for various optical applications.

Long‐term performance and reliability of silicon heterojunction solar modules

AbstractThe high‐efficiency silicon heterojunction (SHJ) technology is now perceived mature enough to enter the Giga‐Watt manufacturing scale with several players around the globe. The growth of the SHJ technology requires confidence from manufacturers, investors, and system developers about its reliability and long‐term performance. In this work, we perform a literature survey collecting performance data (and performance loss rates [PLRs]) published for SHJ modules. Publications on this specific subject are still limited; however, enough available data exist to drive some preliminary conclusions. Despite a long list of caveats specific to this type of meta‐analysis, when considering all published datasets, we obtain for SHJ modules median and average PLR values of 0.56%/year and 0.70%/year, respectively. These numbers are in line with PLR generally reported for field‐deployed crystalline silicon (c‐Si modules). We then apply a filtering procedure to distinguish what we perceive to be high‐accuracy datasets from less accurate ones. This methodology is understandably arbitrary, but it helps increasing the robustness of the present analysis. Our refined analysis leads us to slightly higher PLR for SHJ modules: 0.80%/year and 0.83%/year for median and average values, respectively. These values fall between previously reported PLR of c‐Si and thin‐film modules. Additionally, we observe some mild correlations between the PLRs and the climatic conditions of the installation sites, even if we need to stress that for each climate, we find a large variability, including a PLR value as low as 0.29%/year. We complement the survey with information about the main failure modes reported in the literature for this technology and an analysis of the limits and caveats for this type of study. The most significant one is that the reported numbers refer—for the vast majority—to modules from just one manufacturer (i.e., the first company manufacturing and commercializing the SHJ technology). We finally point out that a deep understanding of the potential weaknesses of the technology—collected over the years—has led to several improvements in terms of reliability. A careful material choice and module design may in fact allow the SHJ technology targeting extended service lifetimes of 35+ years.

Design and Simulation of a PV Solar System with Silicon Hetero-Junction Technology (HJT) for a Residential Stand-Alone "off Grid" System with Batteries Using PV Syst Software in Iraq/Baghdad

Recently, the environment has been negatively impacted by the excessive CO2 emissions caused by the wide usage of fossil fuels in electricity generation. If this continued, it is predicted that the temperature of the atmosphere would rise, causing an increase in storms, hurricanes, droughts, dust, and floods. Therefore, as renewable energy produces little to no emissions, there is an urgent need to adapt it in recent times. Meanwhile, The PV sector has experienced rapid growth in recent years. The PV sector is embracing new technology, and the cell efficiency has been rising rapidly like Silicon Hetero- junction technology HJT which has offered additional benefits: It offers a well-suited application to reach efficiencies above 23% with process temperatures below 200°C. HJT solar panels have &gt;90% module bifaciality and a low temperature coefficient (-0.3 %/C°), and provide additional benefit to the Levelized Cost of Energy LCOE and output power for PV systems. This study intends to assess the efficiency of a residential off-grid system with (HJT) PV panels at a total power of 2.0 kWh and the daily power close to 10 KWh/day with a 48V system in Iraq/Baghdad. PVsyst (7.2.11 version) software has been used for the analysis to calculate the energy output, and enhancing the system design. The characteristics, solar radiation, and ambient temperature are also included in the meteorological data used for evaluation, which is taken from PVsyst's database.

Fully Textured, Production-Line Compatible Monolithic Perovskite/Silicon Tandem Solar Cells Approaching 29% Efficiency.

Perovskite/silicon tandem solar cells are promising avenues for achieving high-performance photovoltaics with low costs. However, the highest certified efficiency of perovskite/silicon tandem devices based on economically matured silicon heterojunction technology (SHJ) with fully textured wafer is only 25.2% due to incompatibility between the limitation of fabrication technology which is not compatible with the production-line silicon wafer. Here, a molecular-level nanotechnology is developed by designing NiOx /2PACz ([2-(9H-carbazol-9-yl) ethyl]phosphonic acid) as an ultrathin hybrid hole transport layer (HTL) above indium tin oxide (ITO)recombination junction, to serve as a vital pivot for achieving a conformal deposition of high-quality perovskite layer on top. The NiOx interlayer facilitates a uniform self-assembly of 2PACz molecules onto the fully textured surface, thus avoiding direct contact between ITO and perovskite top-cell for a minimal shunt loss. As a result of such interfacial engineering, the fully textured perovskite/silicon tandem cells obtain a certified efficiency of 28.84% on a 1.2-cm2 masked area, which is the highest performance to date based on the fully textured, production-line compatible SHJ. This work advances commercially promising photovoltaics with high performance and low costs by adopting a meticulously designed HTL/perovskite interface.

High Lifetime Ga‐Doped Cz‐Si for Carrier‐Selective Junction Solar Cells

Industrial mass production of solar cells is at a transition toward carrier‐selective junction solar cells with passivating contacts such as TOPCon, POLO, or heterojunction technology (HJT). At the same time, many manufacturers consider switching from p‐type Cz‐Si to n‐type Cz‐Si wafers. This contribution indicates that Ga‐doped p‐type Cz‐Si material is still a viable option for the new type of devices while giving an opportunity to benefit from lower wafer cost. The minority carrier diffusion lengths that are an order of magnitude larger than the thickness of the studied HJT and TOPCoRE devices are reported. Stability aspects for operation in the field are discussed. Best TOPCoRE solar cells on Ga‐doped Cz‐Si show a 0.2% higher efficiency than their co‐processed n‐type counterparts.

Synergetic effect of bismuth vanadate over copolymerized carbon nitride composites for highly efficient photocatalytic H2 and O2 generation

The development of copolymerized carbon nitride (CN)-based photocatalysts may support advances in photocatalytic overall water splitting. However, the recombination of charge carriers is the main bottleneck that reduces its overall photocatalytic activity. To overcome this problem, the construction of heterojunction technology has emerged as an effective approach to reduce the charge carrier recombination, thereby improving charge separation and transport efficiency. In this work, an innovative heterojunction was prepared between Quinolinic acid (QA) modified CN (CN-QAx) and novel nanorod-shaped bismuth vanadate (BiVO4) (BiVO4/CN-QAx) for overall water splitting through a simple in-situ solvent evaporation technique. The obtained results show that the synthesized samples have efficient and improved activities for releasing H2 (862.1 μmol/h) and O2 (31.58 μmol/h) under visible light irradiation. Furthermore, an exceptional apparent quantum yield (AQY) of 64.52 % has been recorded for BiVO4/CN-QA7.0 at 420 nm, which might be due to the substantial isolation of photoinducedcharge carriers. Therefore, this work opens up a new channel toward efficient CN-based photocatalysts in the sustainable energy production processes.

Outdoor performance of GaAs/bifacial Si heterojunction four-terminal system using optical spectrum splitting

Bifacial photovoltaics and multijunction systems represent the most promising alternatives to overcome the theoretical limit of single-junction Si photovoltaics, and these solutions can also be combined to achieve higher performances. This work investigates the outdoor performance of a bifacial four-terminal photovoltaic system based on combining a III-V semiconductor with the silicon heterojunction technology. By exploiting the wide band gap energy of GaAs, the bifaciality of the Si heterojunction and the spectrum-splitting capability of dichroic mirrors, an optimal voltage match between mini-modules of the two solar cells was achieved, with an open-circuit voltage mismatch of 4% of the average value. In this study, we demonstrate the full functionality of bifacial operation with a 17% increase of power conversion efficiency throughout the day compared to monofacial operation. Furthermore, we show that though the solar spectrum is subjected to strong variations from morning to afternoon, which lead to changes of the ratio of the GaAs to the Si mini-module short-circuit currents up to 43% throughout the day, the variation of the overall system power conversion efficiency remains quite limited, less than 16% of the maximum value thanks to the efficient coupling of the two mini-modules.

Techno‐economic analysis of the use of atomic layer deposited transition metal oxides in silicon heterojunction solar cells

AbstractThe industry for producing silicon solar cells and modules has grown remarkably over the past decades, with more than a 100‐fold reduction in price over the past 45 years. The main solar cell fabrication technology has shifted over that time and is currently dominated by the passivated emitter and rear cell (PERC). Other technologies are expected to increase in market share, including tunnel‐oxide passivated contact (TOPCon) and heterojunction technology (HJT). In this paper, we examine the cost potential for using atomic layer deposition (ALD) to form transition metal oxide (TMO) layers ( , and aluminium‐doped zinc oxide [AZO]) to use as lower cost alternatives of the p‐doped, n‐doped and indium tin oxide (ITO) layers, respectively, the layers normally used in HJT solar cells. Using a bottom‐up cost and uncertainty model with equipment cost data and process experience in the lab, we find that the production cost of these variations will likely be lower per wafer than standard HJT, with the main cost drivers being the cost of the ALD precursors at high‐volume production. We then considered what efficiency is required for these sequences to be cost effective in $/W and discuss whether these targets are technically feasible. This work motivates further work in developing these ALD TMO processes to increase their efficiency towards their theoretical limits to take advantage of the processing cost advantage.

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.

Optimization of Silicon Heterojunction Interface Passivation on p‐ and n‐Type Wafers Using Optical Emission Spectroscopy

To increase the efficiency in p‐type wafer‐based silicon heterojunction (SHJ) technology, one of the most crucial challenges is the achievement of excellent surface passivation. Herein, chemical passivation techniques known for n‐type technology are successfully applied on p‐type float–zone (FZ) wafers, and wafer surface passivation quality is correlated with parameters from plasma diagnostics, namely crystallization rate and electron temperature indices. It is shown that plasma ignition at higher powers than deposition powers enhances effective minority carrier lifetimes τeff fourfold for p‐ (0.6–2.1 ms) and sixfold for n‐type (0.6–3.2 ms) wafers while giving opportunity to process under lower electron temperature indices during the nucleation phase. A subsequent hydrogen plasma treatment has a further beneficial effect on chemical passivation, leading to high effective minority carrier lifetimes of 4.5 and 3.1 ms, and implies open‐circuit voltages, i‐VOC, of 735 and 720 mV for p‐ and n‐type wafers, respectively. In particular, cell precursors built on p‐type wafers demonstrate excellent surface passivation with τeff and i‐VOC (4.1 ms and 745 mV). Using these process optimizations, SHJ cells on both p‐ and n‐type wafers are fabricated with efficiencies exceeding 21%.

Demonstration of Feeding Vehicle‐Integrated Photovoltaic‐Converted Energy into the High‐Voltage On‐Board Network of Practical Light Commercial Vehicles for Range Extension

The setting up of a practical electrically driven light commercial demonstration vehicle with integrated photovoltaics (PV) is reported. The demonstrator vehicle is equipped with 15 modules based on the crystalline Si/amorphous Si heterojunction technology. The nominal total peak power under standard testing conditions is 2180 Wp. Specifically, the PV‐converted energy is fed into the high‐voltage (HV; 400 V) board‐net for a utilization of the large capacity of the HV battery and thus for direct range extension. The demonstrator vehicle is equipped with irradiation, wind, temperature, magnetic, and global positioning system sensors. Irradiation and temperature as well as the energy flows from modules, maximum power point trackers (MPPTs), low‐voltage buffer battery to HV battery via DC/DC, and from the HV battery to the loads during an exemplarily test drive day (May 31, 2021) are monitored. The range extension obtained at this day on our test route (51° 59′ N, 9° 31′ E) was 36 km, the corresponding CO2 savings account for ≈2.3 kg. The chain efficiency of the electronic components from the input side of the MPPTs to the HV output side of the DC/DC was 68.6%, whereas the DC/DC itself has an average efficiency of 90%.