Tunnel Oxide Passivated Contact Research Articles

Optimization of rear surface morphology in n-type TOPCon c-Si solar cells

Tunnel oxide passivated contact (TOPCon) crystalline silicon (c-Si) solar cells have attracted much attention because of their superior electrical properties such as the lower contact resistivity and better interface passivation at high temperatures. However, the TOPCon c-Si solar cells also have room for further improvement in optical performance, and the embodiment of optical advantages needs to be matched synchronously in electrical aspect. Here, the rear silicon pyramids with different angles have been achieved through solution corrosion to maximize the light absorption in the c-Si substrate. The light absorption for the pyramid angle of less than 30° is better. Compared with the cell samples with rear pyramid for a certain angle, the samples with flat back surface possess better surface passivation, and the contact resistivity can be reduced effectively by increasing the phosphorus doping concentration and adjusting the annealing temperature. Furthermore, the TOPCon c-Si solar cells with flat rear surface covered by 70 nm poly-Si have been demonstrated to increase the conversion efficiency by about 0.15 % vs. the counterpart for poly-Si of 130 nm thickness, and the improvement is mainly due to the increase of JSC and FF by 0.07 mA/cm2 and 0.72 %, respectively.

22.56% total area efficiency of n-TOPCon solar cell with screen-printed Al paste

Screen-printing Ag paste on the rear side of the Tunnel Oxide Passivated Contact solar cells (TOPCon) is still the mainstream method to form electrodes. However, the high price of precious metals increases the cost of TOPCon cells. Al is a cheap and high-performance conductor, and its work function is compatible with the rear side of TOPCon cells. In this study, we used a UV pulse laser (355 nm, 10 ps) to ablate the rear side SiNx passivation layer of TOPCon cells and then printed Al paste with different weight percentages of silicon (Si-wt.%) on the phosphorus-doped polycrystalline silicon (n+-poly-Si) layer to reduce the cost. We investigated the damage mechanism of laser on SiOx/n+-poly-Si/SiNx passivation structure and the contact mechanism between Al paste and n+-poly-Si layer. The results show that the Voc of SiOx/n+-poly-Si/SiNx passivation structure reduced about 6–7 mV when the laser energy density was 0.431 J/cm2. We got the best electrical performance of TOPCon cells printed with Al paste (25 wt%-29 wt% silicon). The open-circuit voltage (Voc) and the conversion efficiency (Eff), have reached 663.60 mV and 22.56 % respectively. Although the efficiency was 9.40 % relative lower than that of TOPCon cells printed with Ag paste, but the cost of Al paste only accounted for 10 % of Ag paste. In the future, the highest Eff of TOPCon solar cells printed with Al paste on the rear side are expected to reach the commercial TOPCon based on Ag paste, which applies laser doping selective emitter technology (SE) and bifacial poly-Si passivation structure.

Advancing nickel seed layer electroplating for enhanced contact and passivation performance in TOPCon solar cells

Electroplating copper technology offers advantages such as low cost, good conductivity, and a simple process, making it a promising solution in the photovoltaics (PV) field. However, despite its effectiveness in reducing silver consumption, a significant challenge arises from suboptimal electrical contact between metal electrodes and the polycrystalline silicon films, limiting the application of electroplating techniques in tunnel oxide passivated contact (TOPCon) solar cells (SCs). In this study, we propose a simple method to enhance the quality of electrodeposited metals and improve contact performance with polycrystalline silicon films by lowering the electrodepositing temperature for nickel seed layer. Additionally, we optimize contact properties by modulating nickel deposition time and annealing temperature. This process results in excellent physical and electrical contact performance, achieving the lowest contact resistivity of 0.19 mΩ cm2 and the improved adhesion strength. Ultimately, TOPCon SCs using low-temperature plated seed nickel and copper metal electrodes achieve an efficiency of 23.90%, which is attributed to advance the application of optimal nickel seed layer electroplating.

Tunnel oxide passivating contact enabled by polysilicon on ultra-thin SiO2 for advanced silicon radiation detectors

Conventional silicon junction detectors encounter significant carrier recombination within the heavily doped p+ and n+ layers, as well as beneath the metal contact regions, creating the so-called “dead layers”, especially on the detector side. In this study, we present the tunnel oxide passivating contact with doped polysilicon on oxide, which demonstrates exceptional surface passivation and carrier selectivity. The key innovation lies in an ultra-thin (~ 1.5 nm) interfacial oxide layer that facilitates efficient majority carrier transportation via tunneling while effectively block minority carriers. Remarkably low saturation current densities, ranging from 5 to 10 fA/cm2 even with the metal contact, underscore the superiority of both n-type and p-type tunnel oxide passivating contacts. In contrast, conventional p–n junction or high-low junction exhibit saturation current densities ranging from 10 to 90 fA/cm2 in the studied p+ and n+ layers with surface passivation schemes due to Auger recombination and surface recombination, and 1000–6000 fA/cm2 with metal contacts due to intense metal-induced recombination at the interface. These findings indicate the potential and superiority of implementing n-type tunnel oxide passivating contact on the detector side and p-type contact on the back side for advanced silicon radiation detectors. This approach would enable thorough collection of generated charge carriers along the track of incident ionizing radiation particles, leading to improved energy resolution and reduced noise levels.

Optimizing phosphorus-doped polysilicon in TOPCon structures using silicon oxide layers to improve silicon solar cell performance

Tunnel Oxide Passivated Contact (TOPCon) technology is one of the most influential and industrially viable solar cell technologies available today. Improving the quality of passivation contact has become a central focus of current research. Although the conventional monolayer polycrystalline silicon method is highly effective in TOPCon solar cells, it is limited by doping inhomogeneity, which impairs the passivation and electrical properties, and the cell's photovoltaic conversion efficiency remains suboptimal. To address this issue, this study investigates the deposition of two layers of silicon oxide and two layers of in-situ doped phosphorus amorphous silicon, termed double poly-Si/SiOx structures, on n-type silicon wafers using plasma-enhanced chemical vapor deposition (PECVD). The effectiveness of the structure was confirmed through various characterization techniques such as scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Key findings indicate that the double-polysilicon structure significantly enhances the uniformity of phosphorus doping, improving the carrier lifetime of the cell and reducing the contact resistance. As a result, the average efficiency in the final production stage has a conversion efficiency gain of 0.23 % over the baseline group. This study underscores the potential of this PECVD methodology to advance the fabrication of high-efficiency solar cells by providing significant improvements in passivation, doping uniformity, and overall cell performance.

Preparation of Al2O3 thin films by RS-ALD and edge passivation application for TOPCon half solar cells

A rotary spatial atomic layer deposition (RS-ALD) method is proposed for the preparation of high-quality Al2O3 thin films and its application to the edge passivation of tunnel-oxide passivated contact (TOPCon) half solar cells. The high- quality Al2O3 thin films were prepared on silicon wafers by optimizing the process conditions with a process pressure of 4 Torr and a trimethylaluminum (TMA, (CH3)3Al) flow rate of 300 sccm. The Al2O3 thin films were annealed to analyse the transformation of the film crystal structure, surface morphology, and passivation properties. Compared to the half solar cells without edge passivation, the efficiency of the cell with only deposited Al2O3 increased by 0.098 %, and the module power increased by 3.08 W. The efficiency of the cell with deposited Al2O3 + annealing increased by a further 0.021–0.119 %, and the module power increased by a further 0.68–3.76 W.

Laser damage and post oxidation repair performance of n-TOPCon solar cells with laser assisted doping boron selective emitter

Boron laser-assisted doped selective emitter (LDSE) is a research hotspot in the mass production of N-type tunnel oxide passivated contact (TOPCon) silicon solar cells. Consequently, it is critical to investigate the damage and repair of laser-assisted doped selective emitter. Through simulation, a surface temperature of silicon rises to over 1414 °C during the laser-assisted doping process, which causes silicon to melt and recrystallize more quickly, and increases the solid solubility of B atoms. Meanwhile, the surface pyramid structure was partially destroyed or even collapsed. The results showed that the peak intensity of (211) crystal planes decreased while the peak intensity of (400), (311), and (220) crystal planes increased. This led to an increase in surface defects and suspension bonds, resulting in an increase in J0,passivated up to 246.3 fA/cm2. The laser-induced damage can be successfully repaired by the post-oxidation process, reducing J0,passivated to 45.07 fA/cm2. The Quokka simulation indicates that a laser pulse fluence of 2.78 J/cm2 can increase the efficiency of the LDSE cell by 0.31 %. It does not necessarily lead to the greater efficiency gains with higher laser pulse fluence owing to the increase in surface damage. Exploiting the laser assisted doping method with a minimal surface damage, a wide process window and low cost will be the next major challenge.

The differences between the hydrogenation by means of photon-injection and electron-injection for N-type tunnel oxide passivated contacts solar cells

Tunnel Oxide Passivated Contact (TOPCon) solar cells have received widespread attention in recent years, especially in improving conversion efficiency. This paper investigated the impact of hydrogenation technology using photon-injection (HPI) and electron-injection (HEI) processes on TOPCon solar cells, highlighting the higher improvement effect and broader application scope of HPI compared to HEI. In TOPCon cells, several methods are available to prepare the tunneling oxide layer, such as plasma oxidation (PO) and indirect thermal oxidation (TO). The research results indicated that significant improvement differences could be observed when utilizing the HEI treatment for TOPCon solar cells prepared by PO and TO methods, with values of 0.133%abs. and −0.039%abs., respectively. Meanwhile, HPI treatment induced a more significant efficiency improvement for these two types of cells, and the increase in efficiency is 0.247%abs. and 0.244%abs., respectively. The experimental results demonstrated that the passivation effect for TOPCon solar cells prepared by PO and TO methods remained almost the same under the HPI treatment, and the improvement effect is less dependent on the tunnel oxidation technique used. Thus, the different passivation effects between HPI and HEI were further investigated, and the reason for the difference was attributed to the charge states and concentrations of hydrogen and non-equilibrium carriers during the hydrogenation. The results provided an improved scheme for enhancing the efficiency of TOPCon solar cells, shedding light on the role of HPI and HEI in the passivation process. This work brings further insights to TOPCon solar cells.

Optimizing the metallization process for high fill factor of n-type crystalline silicon TOPCon solar cells

The primary challenge in solar cell manufacture concerning the metallization process is the need to achieve a balance between the electrical and optical performance of the metal contacts as the contribute to shading and the series resistance (Rs) of solar cells. Addressing these challenges with the optimization of the metallization process is crucial for achieving a high fill factor (FF) in solar cells, as FF is a key parameter indicating the quality and efficiency of a solar cell. An impact of different snap-off, distances between mask and cells, of n-type TOPCon (Tunnel Oxide Passivated Contact) solar cells during the screen-printing process was conducted. This experiment employs testing and analysis to determine the most effective snap-off distance that minimizes the Rs variability, resulting in an overall enhancement in cell efficiency. The smaller snap-off distance can lead to better performance in n-TOPCon solar cells due to finer lines, uniform contacts, and lower Rs. The I-V characteristics of 1.4 mm are Jsc of 39.58 mA/cm2, Voc of 684.63 mV, FF of 80.54 %, and power conversion efficiency (PCE) of 21.83 %, respectively. In addition, dark I-V measurement is essential for diagnosing performance issues; we got shunt resistance (Rsh) of 4.97 x 106 Ω which is the highest value that indicates minimal Rs of 0.3 Ω. As a result, it is a potential strategy for n-TOPCon solar cell improvements.

Buyer aware: Three new failure modes in TOPCon modules absent from PERC technology

The n-type tunnel oxide passivated contact (TOPCon) technology is going to be the leading industrial technology in 2024. However, there are still concerns about the reliability of TOPCon when used in the field, especially in glass/backsheet modules. This work investigates the impact of damp heat (DH) on the performance TOPCon and PERC glass/backsheet modules by varying bills of materials (BOM), such as polyolefin elastomer (POE), ethyl-vinyl acetate (EVA), and polymer backsheet options. It is found that PERC modules remain stable, with a maximum power loss (Pmax) of only 1–2%rel after 1000 h of DH testing, regardless of the BOM used. However, TOPCon modules experienced significant degradation with a drop in Pmax ranging from 4 to 65%rel after the same testing duration. Despite utilizing POE, an expensive encapsulant with a significantly lower water vapour transmission rate than EVA and devoid of acetic acid formation, a severe performance decline was observed in a specific POE variant within TOPCon modules, with a loss of power of up to 65%rel. Three types of failures were observed in TOPCon modules: point-localized failure, failure at/around the interconnection of ribbon wires and busbars, and failure throughout the whole area of cells/modules. These failures likely result from electrochemical reactions involving moisture, cell metallization, ribbon wires, contaminants, soldering flux, and additives released from POE. The observed findings underline two crucial points: 1) the vulnerability and potential failure of TOPCon solar cells when exposed to high humidity and contaminants, and 2) the high risk associated with certain POE types, which could potentially adversely affect TOPCon cells. Hence, it is crucial to exercise utmost caution and precision in handling and selecting encapsulation materials for TOPCon modules. Accordingly, urgent and extensive research efforts are crucial to substantially increase our comprehension and fortify the reliability of TOPCon cells against the pernicious effects of moisture and other contaminants.

Highly Transparent Oxygen‐Doped Poly‐Si with In‐situ N2O Oxidant for Poly‐Si Passivating Contacts in Perovskite/Silicon Tandem Solar Cells

Tunnel oxide passivated contact (TOPCon) silicon solar cells have been developed and transferred into industrial mass production, which is beneficial to the future production of perovskite/silicon tandem solar cells (TSCs) in a large scale. However, the doped polycrystalline silicon (poly‐Si) layer in the poly‐Si‐based passivating contact structure yields a profound optical loss from reflection and parasitic absorption, which obstacles the efficiency promotion of TSCs. In this work, the optical property of poly‐Si is improved by in‐situ oxygen incorporation using plasma enhanced chemical vapor deposition (PECVD) with nitrous oxide (N2O) as the oxygen source. The p‐type oxygen‐incorporated poly‐Si (poly‐SiOx) shows a reduced refractive index and extinction coefficient over 700–1200 nm wavelength, leading to a reduced reflection, a lower parasitic absorption and a higher transmission. After applying an optimized p‐type oxygen‐incorporated poly‐Si in the front‐side poly‐Si passivating contact structure of c‐Si bottom cell, the short‐circuit current density and efficiency of a perovskite/c‐Si tandem cell increases by ≈0.32 mA cm−2 and ≈0.8%, respectively, leading to 25.12% tandem cell efficiency.

Comparative Study on Energy Yield of Tunnel Oxide Passivated Contact (TOPCon) and Passivated Emitter and Rear Contact (PERC) Solar Cells and Analysis of Optimal Installation Method for Vertical Photovoltaics

Photovoltaic (PV) installations have traditionally relied on a conventional south-facing orientation, which maximizes energy production at noon but has lower energy generation in the morning and afternoon. Vertical photovoltaic (VPV) systems have emerged as promising alternatives to address this inconsistency. Vertical photovoltaic systems can enhance energy generation by facing east in the morning and west in the afternoon. We compared the performance of n-tunnel oxide passivated contact (n-TOPCon) and p-passivated emitter and rear contact (p-PERC) cells in vertical photovoltaic systems to determine whether the optimal installation direction of bifacial vertical photovoltaics is east or west. Our findings indicated that n-TOPCon cells exhibited higher energy yields than p-PERC cells, with a difference of approximately 8%, attributed to the superior bifaciality and lower temperature coefficient of power of n-TOPCon. Additionally, the energy yield was higher for n-TOPCon modules when the front faced east, whereas the PERC modules performed better with a west-facing front. This contributes to the knowledge of the factors for energy production in vertical photovoltaic systems and the optimization of installation configurations.

Progress in TOPCon solar cell technology: Investigating hafnium oxide through simulation

In the realm of solar energy technology, exploring hafnium oxide (HfO2) in Tunnel Oxide Passivated Contact (TOPCon) solar cells is pivotal. This study delineates HfO2's evolution from semiconductor applications, highlighting its crucial role in enhancing TOPCon solar cell performance. Utilizing ATLAS Silvaco software, the study anticipates a 21.3% increase in charge carrier lifetime through optimized HfO2 layers, addressing challenges in interface engineering and scalability. Innovative research integrates hafnium oxide (HfO2) into TOPCon solar cells, marking a leap in photovoltaic technology. Utilizing ATLAS Silvaco simulations, it shows that HfO2 layers can significantly enhance cell performance, increasing charge carrier lifetime by 21.3% and potentially boosting efficiency by 25%. This underscores HfO2's advantages, like a higher dielectric constant and thermal stability, in improving solar cell efficiency and durability. Future efforts target refining deposition processes, projecting a 25% boost in overall power conversion efficiency (PCE). Emphasizing HfO2's significance in solar cell technology, this research contributes to global sustainable energy initiatives. Integrating HfO2 in TOPCon solar cells signifies a key achievement in harnessing clean, renewable energy. Upcoming research focuses on experimental validation, interface engineering, optimization, stability assessments, scalability, and collaborative studies, aiming to leverage HfO2's potential for elevating solar energy conversion technologies.

Ultrafast laser-annealing of hydrogenated amorphous silicon in tunnel oxide passivated contacts for high-efficiency n-type silicon solar cells

The tunnel oxide passivated contact (TOPCon) concept has been the brightest star in the field of emerging passivating contact techniques for the last few years. It has shown great potential in industrial applications due to the overwhelming advantages of high device efficiency and low cost. Here, we introduce a novel crystallization method using ultrafast laser-annealing by scanning a laser spot onto the surface of hydrogenated amorphous silicon film in TOPCon solar cells. By circumventing the high-temperature environment of the conventional annealing process, it can prevent a large number of dopant atoms from penetrating inside the crystalline silicon (c-Si) substrate, reducing the Auger recombination. Moreover, we can conduct extensive experiments to clarify the optimal conditions, including laser-annealing modes and process parameters. The hydrogenation experiments reveal that direct appropriation of the traditional hydrogenation method is not applicable. An additional ‘dehydrogenation’ step proves necessary, indicating that the differences in hydrogen content within the films due to the divergence between the principles of laser-annealing and high-temperature annealing are probably responsible for this. Consequently, the proof-of-concept devices using laser-annealing technology realize a champion efficiency of 19.91%,highlighting an alternative technical route with substantial potential to achieve high-efficiency crystalline silicon solar cells.

High-efficiency TOPCon solar cell with superior P + and P++ layer via one-step processing

The boron diffusion process in the front field of N-type tunnel oxide passivated contact (TOPCon) solar cells is crucial for PN junction formation and the creation of a selective emitter. This study presents a theoretical model of boron diffusion in silicon using molecular dynamics. The research examines the mean square displacement and diffusion coefficient of boron atoms at varying temperatures, confirming their diffusion behavior. The simulations indicate predominant boron diffusion in the z-direction within the silicon matrix, with the diffusion depth being temperature dependent. The optimal temperature range for boron diffusion in silicon is identified as 950 °C to 1050 °C. Using boron-doped silicon paste and boron trichloride as dopants, thermal diffusion experiments were conducted to fabricate the front-field PN junction (p+ layer) and selective emitter (p++ layer) by one step. Subsequent processing and performance evaluation were performed on a production line. Experimental findings reveal a decrease in boron diffusion at higher temperatures, reduced sheet resistance, increased doping concentration, and deeper junction formation. The ideal boron concentration in the p+ layer is 8.68 × 1018 atom/cm3 with a depth of 0.53 μm, while the p++ layer is 2.35 × 1019 atom/cm3 and 0.82 μm. The efficiency of the optimized TOPCon + cell production line reaches up to 25.17 %, marking an improvement of 0.23 % over the standard cell production line. This research contributes to elucidating the mechanism of boron diffusion and offers insights for enhancing the efficiency of TOPCon solar cells.

Bi-layer in-situ phosphorus doped poly-Si films by PECVD for blistering-free high-efficiency industrial TOPCon solar cells

The passivating contact concept stands out as one of the most promising and industrially viable photovoltaic (PV) technologies. Further improving the quality of physical contact has become a focus of ongoing research. The film blistering issue has been identified as one of the major bottlenecks for the polysilicon (poly-Si) films deposited by the PECVD approach. In this study, we investigated how the in-situ phosphorus (P) doping level within the poly-Si films contributes to the occurrence of blistering. Our investigations into the film blistering mechanisms reveal that a high in-situ P-doping suppresses hydrogen release levels and reduces the accumulation of residual stress during annealing, which leads to the blistering-free appearance, especially observed in heavily P-doped poly-Si films. However, as excessive P-doping could weaken the interfacial passivation quality, we propose a bi-layer structure of P-doped poly-Si films which allows the doping profile to be tailored and maintain good quality passivating contacts. Based on the bi-layer structure, we fabricated industrial-sized tunnel oxide passivated contact (TOPCon) solar cells, which attained an average efficiency of 23.84%. Our work not only presents a promising strategy for improving the performance of passivating contacts via the PECVD approach but also underscores the significant potential for its widespread implementation in industrial TOPCon solar cell manufacturing.

Field‐representative evaluation of PID‐polarization in TOPCon PV modules by accelerated stress testing

AbstractPotential‐induced degradation‐polarization (PID‐p) can reduce module power, but how to project the extent to which PID‐p may occur in field conditions considering the factors of system voltage, condensed moisture, temperature, and illumination has not been clarified. Using tunnel oxide passivated contact (TOPCon) modules, this work demonstrates a method to test full‐size crystalline silicon PV modules for PID‐p to provide field‐representative results. In initial screening tests with positive or negative 1000 V electrical bias applied at 60°C for 96 h using Al foil electrodes on the glass surfaces, the module type exhibited reversible PID‐p only on the front face when the cell circuit was in negative voltage potential. No PID was detected on the rear after testing in either polarity. We then evaluated the PID‐p sensitivity on the front side under different UV irradiances while maintaining the glass surface wet to estimate real‐world susceptibility to PID‐p. The magnitude of the observed behavior was fit using a previously developed charge transfer and depletion by light model. Whereas power loss with −1000 V applied to the cell circuit at 60°C for 96 h in the dark was about 30%, testing the module front under 0.051 W·m−2 nm−1 at 340 nm UVA irradiation using fluorescent tubes, the mean degradation was only 3%. When the modules were tested in the dark for PID‐p with in situ dark current–voltage (I‐V) characterization, the thermal activation energy for degradation was 0.71 eV; for recovery in the dark, it was 0.58 eV. Whereas recovery from the degraded state at 60°C in the dark without voltage bias was 5% absolute in 38 h, rapid recovery of about 5% absolute was observed with 1000 W·s/m2 exposure at 25°C using a flash tester.

Data-Driven Tunnel Oxide Passivated Contact Solar Cell Performance Analysis Using Machine Learning.

Tunnel oxide passivated contacts (TOPCon) have gained interest as a way to increase the energy conversion efficiency of silicon solar cells, and the International Technology Roadmap of Photovoltaics forecasts TOPCon to become an important technology despite a few remaining challenges. To review the recent development of TOPCon cells, this work has compiled a dataset of all device data found in current literature, which sums up to 405 devices from 131 papers. This may seem like a surprisingly small number of cells given the recent interest in the TOPCon architecture, but it illustrates a problem of data dissemination in the field. Notwithstanding the limited number of cells, there is a great diversity in cell manufacturing procedures, and this work observes a gradual increase in performance indicating that the field has not yet converged on a set of best practices. By analyzing the data using statistical methods and machine learning (ML) algorithms, this work is able to reinforces some commonly held hypotheses related to the performance differences between different device architectures. This work also identifies a few more unintuitive feature combinations that would be of interest for further experimentally studies. This work also aims to inspire improvements in data management and dissemination within the TOPCon community.

AFORS-HET-based numerical exploration of tunnel oxide passivated contact solar cells incorporating n- and p-type silicon substrates.

The development of a tunnel oxide interfacial layer capped by a highly doped poly-Si layer is considered one of the most promising methods to reduce charge carrier recombination and improve the performance of conventional PERC devices. The thickness and doping concentration of emitters and BSF layers greatly influence the tunnelling current in TOPCon devices. In this research, we evaluated the performance of tunnel oxide passivated contact (TOPCon) solar cells by conducting an in-depth analysis of various key parameters. The parameter include the type of silicon substrate (n or p-type); the thickness and doping density (N a/N d) of n, n+, p, and p+ layers; and surface recombination velocity (front/rear), which were analyzed using AFORS-HET simulation software. A comparative analysis of performance demonstrates that the highest efficiency is achieved in the n-TOPCon solar cell with the following values: V oc = 660.2 mV, J sc = 45.05 mA cm-2, FF = 82.87%, and PCE = 25.74%. In the optimized p-TOPCon solar cell, the open circuit voltage (V oc) and fill factor (FF) exhibit improvements of 35.9 mV and 0.39%, respectively. However, the values of J sc and PCE decrease by 6.44 mA cm-2 and 2.2%, respectively, in p-TOPCon solar cells. Furthermore, photo-electroluminescence analysis reveals that the n-TOPCon solar cells exhibit a higher maximum photon flux (front/rear) than p-TOPCon solar cells.

Blistering-free carbon-doped polysilicon (n+) passivating contact with high surface passivation properties prepared by industrial tube PECVD

Tube plasma-enhanced chemical vapor deposition (PECVD) has garnered attention as a promising large-scale production tool for in-situ doped polysilicon due to its high capacity and low equipment cost. In this work, we explore the use of carbon (C)-doped a-Si:H (n+), deposited by tube PECVD, for tunnel oxide passivated contact (TOPCon) solar cells. By introducing carbon atoms into polysilicon, blistering-free polysilicon films with excellent passivation properties can be obtained. The optimized sample with C-doped polysilicon (n+) exhibits remarkable surface passivation with a single-sided saturation current density (J0,s) of 1.25 fA/cm2, an implied open-circuit voltage (iVoc) of 751 mV, and a corresponding effective lifetime exceeding 18 ms at a minority carrier concentration of 1 × 1015 cm−3. UV Raman measurements reveal that C doping suppresses the crystallization of polysilicon, leading to a significant stress in the film. Despite excessive C doping, the contact resistivity extracted from the TLM method remains below 13.6 mΩ cm2. As a result, a champion conversion efficiency of 23.64 % was achieved in a small-sized proof-of-concept n-type TOPCon solar cell. This demonstrates the feasibility of fabricating C-doped polysilicon (n+) prepared by tube PECVD for high-efficiency and low-cost TOPCon solar cells.