Excellent Passivation Properties Research Articles

Boron‐Doped Zinc Oxide Electron‐Selective Contacts for Crystalline Silicon Solar Cells with Efficiency over 22.0%

The exploration of wide‐bandgap metal compound films with excellent passivation and contact properties on crystalline silicon (c‐Si) surface, as alternatives to traditional‐doped Si thin films, holds significant promise for the future enhancement of c‐Si solar cell efficiency. Herein, conductive boron‐doped zinc oxide (ZnO:B) films are deposited by atomic layer deposition (ALD) process and investigated as electron‐selective contacts, in combination with a thin SiOx passivating interlayer. This combination demonstrates a relative low contact resistivity of ≈2 mΩ cm2 and improved passivation quality. Further application of this SiOx/ZnO:B stack as a full‐area electron‐selective passivating contact in proof‐of‐concept n‐type c‐Si solar cells results in a satisfactory power conversion efficiency of over 22.0%. This electron‐selective passivating contact structure, prepared via low‐temperature, simplified, and the compositionally controlled ALD process, offers a promising pathway for the development of high‐efficiency and low‐cost c‐Si solar cells.

Enhanced passivation of lead and cadmium from contaminated farmland using biochar with tailored pore properties: Performance and mechanisms

The porous biochar (PBCPB) was prepared by one-step KHCO3-activated pyrolysis of corn stalks, which showed excellent passivation properties for Pb/Cd in soil (48.99 % or 46.74 %). Characterization results revealed that the PBCPB possessed a dense and network-like pore structure with a huge specific surface area of 1342.07 m2/g, which was conducive to the passivation of Pb/Cd. Batch experiments showed that PBCPB had excellent adsorption properties with the maximum absorption capacity of 117.61/48.24 mg/g. After 30 d of remediation, the bioavailable-Pb/Cd contents in 5.0 % of PBCPB treatment were reduced by 47.06 % and 58.42 %, respectively. The speciation transformation results uncovered that the contents of unstable Pb/Cd components gradually decreased with the increase of PBCPB dosages, ultimately transforming into stable residual components. In addition, the PBCPB could effectively increase the contents of soil available nutrients and enhance functional enzyme activities, which contributed to promoting the growth of cucumber seedlings. Meanwhile, PBCPB strongly alleviated the oxidative damage of Pb/Cd to cucumber seedlings by significantly reducing the Pb/Cd accumulation and antioxidant oxidase activity of cucumber seedlings. Furthermore, precipitation, complexation, as well as cation-π interaction were the primary passivation mechanisms of PBCPB for Pb/Cd. Overall, the study provided a reasonable design of porous carbon-based materials for the remediation of Pb/Cd-contaminated soil.

Low-temperature fabrication of boron-doped amorphous silicon passivating contact as a local selective emitter for high-efficiency n-type TOPCon solar cells

Tunnel oxide passivating contact (TOPCon) solar cells (SCs) currently dominate the photovoltaic industry but grapple with efficiency challenges. A primary concern is the direct contact between front-sided metal electrodes and boron emitters, resulting in substantial carrier recombination losses and limiting further efficiency improvements. Here, we introduce a low-temperature approach to deposit a local boron-doped amorphous silicon [a-Si:H(p)] between front-sided metal electrodes and boron emitters. This method, avoiding issues associated with high-temperature processes, demonstrates excellent passivation and contact properties, featuring the lowest contact resistivity (< 1 mΩ·cm2) and a low saturation current density (< 400 fA/cm2). The outstanding passivation and contact properties remain robust even with variations in diborane flow rates during a-Si:H(p) fabrication, annealing temperatures, and sheet resistances of boron emitters. We elucidate the factors contributing to the enhanced passivation observed in boron emitters with a-Si:H(p) through a combination of simulations and experiments. The a-Si:H(p) layer between boron emitters and metal electrodes acts as a protective barrier, preventing the diffusion of metal atoms and suppressing carrier recombination. A heterojunction is formed between a-Si:H(p) and the boron emitter, facilitating electric-field passivation. Consequently, the TOPCon SCs incorporating a-Si:H(p) achieve an efficiency of 24.50%, surpassing their counterparts without a-Si:H(p) (23.11%). This work utilizes low-temperature technology to achieve fully passivated contact, providing insights for the development of high-efficiency TOPCon SCs.

Development of n-Type, Passivating Nanocrystalline Silicon Oxide Films via Plasma-Enhanced Chemical Vapor Deposition

Nanocrystalline silicon oxide (nc-SiOx:H) is a multipurpose material with varied applications in solar cells as a transparent front contact, intermediate reflector, back reflector layer, and even tunnel layer for passivating contacts, owing to the easy tailoring of its optical properties. In this work, we systematically investigate the influence of the gas mixture (SiH4, CO2, PH3, and H2), RF power, and process pressure on the optical, structural, and passivation properties of thin n-type nc-SiOx:H films prepared in an industrial, high-throughput, plasma-enhanced chemical vapor deposition (PECVD) reactor. We provide a detailed description of the n-type nc-SiOx:H material development using various structural and optical characterization techniques (scanning electron microscopy (SEM), energy dispersive X-ray (EDX), Raman spectroscopy, and spectroscopic ellipsometry) with a focus on the relationship between the material properties and the passivation they provide to n-type c-Si wafers characterized by their effective carrier lifetime (τeff). Furthermore, we also outline the parameters to be kept in mind while developing different n-type nc-SiOx:H layers for different solar cell applications. We report a tunable optical gap (1.8–2.3 eV) for our n-type nc-SiOx:H films as well as excellent passivation properties with a τeff of up to 4.1 ms (implied open-circuit voltage (iVoc)~715 mV) before annealing. Oxygen content plays an important role in determining the crystallinity and hence passivation quality of the deposited nanocrystalline silicon oxide films.

Constructing an Ion‐Wall to Achieve Excellent Lithium Anodes in Li–O2 Batteries with High DN Electrolytes

AbstractFor the lithium (Li) metal anode, constructing a strong and durable protective layer with lithium‐ion permeability is crucial, especially in high donor number (DN) solvent system. High DN solvent‐based electrolytes can support both higher capacity and lower charge overpotential in the rechargeable lithium–oxygen batteries (LOBs). However, Li anodes in high DN solvent system suffer from severe corrosion and uncontrolled dendrite growth due to the unstable solid‐electrolyte interphase (SEI). Typically, this interface is formed in situ through electrochemical processes with complicated component and spatial distribution. Here, a functional molecule is introduced to construct an ion‐wall (IW) on Li surface by prechemical sequential reactions (p‐CSRs), through which the crystalline nanoparticles as bricks and amorphous hybrid compounds as the mortar can be produced to build such a “wall.” Different from the conventional SEI, this wall is not only compact and uniform, but also possess high strength, excellent passivation properties and high ionic conductivity. With these properties, the IW could suppress Li dendrites and inhabit the side reaction, supporting highly reversible Li plating/stripping behavior in high DN solvent system. As a result, the cycle stability of LOBs based on the IW protected Li anode is significantly improved.

Sn‐Doped Nb2O5Films as Effective Hole‐Selective Passivating Contacts for Crystalline Silicon Solar Cells

Carrier‐selective contacts (CSCs) in crystalline silicon (c‐Si) solar cells have attracted great attention due to suppressing contact region recombination and achieving higher conversion efficiency. Among transition metal oxides for CSCs, niobium oxide (Nb2O5) is considered as an attractive candidate for electron‐selective contact due to its excellent passivation properties and small conduction band offsets with c‐Si. Nevertheless, the performance of c‐Si solar cells employing Nb2O5contact layer has not been explored yet. Herein, the carrier selectivity of solution‐processed Nb2O5films is investigated for c‐Si. Interestingly, Nb2O5exhibits high electron‐blocking performance and low contact resistivities with p‐Si. The ultra‐thin SiOxinterlayer formed by UV–O3pretreatment further reduces the contact resistivities and increases minority carrier lifetime due to the improved contact interface. The Sn4+doping improves the work function of Nb2O5to induce larger upward band bending at c‐Si surface, thus enhancing the hole selectivity. As a result, p‐type c‐Si solar cells with solution‐processed Nb2O5hole‐selective contact layer have achieved the highest power conversion efficiency of 18.4%, with a high‐thermal stability superior to the typical hole transport layers. This work first demonstrates the exceptional hole selectivity of Nb2O5, which shows very promising applications in high‐efficiency c‐Si 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.

Regionalizing Nitrogen Doping of Polysilicon Films Enabling High-Efficiency Tunnel Oxide Passivating Contact Silicon Solar Cells.

Tunnel oxide passivating contact (TOPCon) solar cells (SCs) as one of the most competitive crystalline silicon (c-Si) technologies for the TW-scaled photovoltaic (PV) market require higher passivation performance to further improve their device efficiencies. Here, the successful construction of a double-layered polycrystalline silicon (poly-Si) TOPCon structure is reported using an in situ nitrogen (N)-doped poly-Si covered by a normal poly-Si, which achieves excellent passivation and contact properties simultaneously. The new design exhibits the highest implied open-circuit voltage of 755mV and the lowest single-sided recombination current density (J0 ) of ≈0.7 fAcm⁻2 for a TOPCon structure and a low contact resistivity of less than 5 mΩ·cm2 , resulting in a high selectivity factor of ≈16. The mechanisms of passivation improvement are disclosed, which suggest that the introduction of N atoms into poly-Si restrains H overflow by forming stronger Si-N and N-H bonds, reduces interfacial defects, and induces favorable energy bending. Proof-of-concept TOPCon SCs with such a design receive a remarkable certified efficiency of 25.53%.

Enhancement of NiOx/Poly‐Si Contact Performance by Insertion of an Ultrathin Metallic Ni Interlayer

Nickel oxide () is a promising hole transport material for perovskite/Si tandem solar cells. Various silicon cell architectures may be used as bottom cells. The polycrystalline (poly‐Si) tunnel diode is expected to be a high‐efficiency interconnection scheme between the two subcells of monolithic tandems in p‐i‐n configuration with a high thermal budget, excellent passivation properties, and low contact resistivity. However, is then interfaced to poly‐Si() and the chemical integrity of the interface due to the necessity of annealing treatments has to be questioned. For this purpose, the /poly‐Si contact resistivity for different annealing temperatures is investigated between 100 and 500 °C, and two different deposition techniques, namely, wet‐chemically applied and sputter‐deposited . The values of more than are obtained. The insertion of a nm‐thin metallic Ni interlayer is shown to enable a tremendous decrease of the contact resistivity by 2–3 orders of magnitude. The formation of is proven by highly resolved (scanning) transmission electron microscopy ((S)TEM) coupled with energy‐dispersive X‐ray spectroscopy (EDXS). This interfacial engineering approach is expected to provide an effective way of improving the contact properties and integrability of into various tandem cell processes.

Excellent surface passivation of p-type TOPCon enabled by ozone-gas oxidation with a single-sided saturation current density of ∼ 4.5 fA/cm2

High-quality p-type tunnel oxide passivated contact (p-type TOPCon) is a feasible technical solution to further improve the efficiency of TOPCon silicon solar cells. Plasma-enhanced chemical vapor deposition (PECVD) technology route could deposit boron-doped amorphous silicon film in-situ and thus becomes one of the most promising industry routes to prepare the TOPCon structure. However, the passivation quality of p-type TOPCon by PECVD is not satisfactory till now. In this work, we develop the high-performance p-type TOPCon technology by integrating the ozone-gas oxidation to prepare the ultra-thin SiOx film, which shows excellent passivation and contact properties. The experimental results suggest that the double-sided p-type TOPCon passivated samples with p-type Si substrates receive a maximal implied open-circuit voltage (iVoc) of ∼ 734 mV together with a minimum single-sided saturation current density (J0,s) of ∼ 4.5 fA/cm2. Correspondingly, the contact resistivity is less than 5 mΩ·cm2, yielding a high selectivity S10 of 15.6, which is one of the best values for p-type TOPCon technology. As a result, the precursor cell manifests an excellent iVoc of 717 mV, and the p-type silicon solar cell with rear-sided p-type TOPCon passivating contact receives a high efficiency of 22.23%. Generally, this work provides a promising technology for preparing the high-quality p-type TOPCon passivating contact for industrial application.

Improvement of the corrosion performance of a cold-rolled Co40Cr20Ni30Al5Ti5 high-entropy alloy by adjusting annealing treatments

High-entropy alloys (HEAs) are expected to possess various excellent properties due to their vast composition design space and unique core effects. Annealing treatments after cold rolling are widely discussed as an effective means to improve the overall performance of the alloy. Nevertheless, the effect of annealing treatments on the corrosion resistance of cold-deformed alloys is still somewhat controversial. Therefore, cold rolling and annealing at different temperatures are performed on the Co40Cr20Ni30Al5Ti5 high-entropy alloy to investigate the effect of annealing temperature on its corrosion behavior. The annealing temperature range covers all stages of the HEA recovery-recrystallization-grain growth (in 50 °C gradients). The experimental results show that the HEA recrystallization is fundamentally complete at 850 °C and fully austenitized at 1050 °C. The best corrosion resistance performance is observed at 850 °C, with the lowest corrosion current density (ipass) and the lightest pitting in full immersion experiments. In addition, excellent passivation properties, such as the lowest steady-state current density iss and highest passivation film growth rate, are achieved at 850 °C. Further analyses of the growth films also show that the passivation films formed at 850 °C are thicker and uniform, and additionally have the highest Cr2O3 content. Accordingly, the effects of annealing temperature on HEA corrosion resistance and passivation behavior are discussed. The superior corrosion resistance and passivation behavior at 850 °C are attributed to the coupling of grain size and passivation film composition. The current findings might guide the optimized design of future cold-deformed alloys for better corrosion resistance.

Electronic Characteristics of Ultra‐Thin Passivation Layers for Silicon Photovoltaics

AbstractSurface passivating thin films are crucial for limiting the electrical losses during charge carrier collection in silicon photovoltaic devices. Certain dielectric coatings of more than 10 nm provide excellent surface passivation, and ultra‐thin (&lt;2 nm) dielectric layers can serve as interlayers in passivating contacts. Here, ultra‐thin passivating films of SiO2, Al2O3, and HfO2 are created via plasma‐enhanced atomic layer deposition and annealing. It is found that thin negatively charged HfO2 layers exhibit excellent passivation properties—exceeding those of SiO2 and Al2O3—with 0.9 nm HfO2 annealed at 450 °C providing a surface recombination velocity of 18.6 cm s−1. The passivation quality is dependent on annealing temperature and layer thickness, and optimum passivation is achieved with HfO2 layers annealed at 450 °C measured to be 2.2–3.3 nm thick which give surface recombination velocities ≤2.5 cm s−1 and J0 values of ≈14 fA cm−2. The superior passivation quality of HfO2 nanolayers makes them a promising candidate for future passivating contacts in high‐efficiency silicon solar cells.

Experimental and Numerical Simulation of Molybdenum Oxide Films with Wide Bandgap and High Work Function for Carrier-Selective Contact Solar Cells

In silicon heterojunction (SHJ) solar cells, a wide bandgap material with a high work function is widely used as the hole extraction pathway to attain high efficiency. We introduced a molybdenum oxide (MoOx) film as an effective hole-transfer layer in carrier selective contact (CSC) solar cells by virtue of its wide bandgap along with high work function. The passivation characteristics, optical and electrical properties of MoOx films were investigated by differing thickness and work function. The combination of 6 nm hydrogenated intrinsic amorphous silicon (a-Si:H(i)) and 7 nm thermally evaporated MoOx passivation layers provides excellent passivation properties, reduces carrier recombination, and improves the cell performance. The synthesized CSC solar cells showed promising results, with an open-circuit voltage (Voc) of 708 mV, short-circuit current (Jsc) = 37.38 mA cm−2, fill factor (FF) = 74.59%, and efficiency (η) = 19.75%. To justify the obtained result, an AFORS HET simulation was conducted based on the experimental results. The high work function and wide bandgap MoOx/c-Si(n) interface developed a considerable built-in potential and suppressed the electron–hole pair recombination mechanism. The CSC solar cell’s simulated performance was enhanced from 1.62 to 23.32% by varying the MoOx work function (ΦMoOx) from 4.5 to 5.7 eV.

Al2O3/MoOx Hole-Selective Passivating Contact for Silicon Heterojunction Solar Cell

Carrier selective contact (CSC) layers have been extensively studied to realize high passivation effect in solar cells. Excellent passivation properties of Al2O3 and a-Si:H(i) as passivating interlayers between the hole-selective contact (HSC) MoOx and p-type c-Si wafer surface are reported herein. MoOx single layer exhibits a high work function value (≥5.0 eV), which can cause sufficient band bending in the band structure for HSC. An Al2O3/MoOx contact exhibits a significantly higher transmittance and surface passivation compared with that of an a-Si:H(i)/MoOx contact. The passivation results for Al2O3/MoOx contact are a carrier lifetime (τeff) of 830 μs and implied open circuit voltage (iVOC) of 726 mV, whereas for conventional a-Si:H(i)/MoOx contact, the corresponding values are 770 μs and 716 mV. Delicate thickness optimization was performed using experimental and simulation results for Al2O3/MoOx and a-Si:H(i)/MoOx stacks to achieve high performance in p-type c-Si solar cells.

Numerical Simulation and Experiment of a High-Efficiency Tunnel Oxide Passivated Contact (TOPCon) Solar Cell Using a Crystalline Nanostructured Silicon-Based Layer

We report on the tunnel oxide passivated contact (TOPCon) using a crystalline nanostructured silicon-based layer via an experimental and numerical simulation study. The minority carrier lifetime and implied open-circuit voltage reveals an ameliorated passivation property, which gives the motivation to run a simulation. The passivating contact of an ultra-thin silicon oxide (1.2 nm) capped with a plasma enhanced chemical vapor deposition (PECVD) grown 30 nm thick nanocrystalline silicon oxide (nc-SiOx), provides outstanding passivation properties with low recombination current density (Jo) (~1.1 fA/cm2) at a 950 °C annealing temperature. The existence of a thin silicon oxide layer (SiO2) at the rear surface with superior quality (low pinhole density, Dph &lt; 1 × 10−8 and low interface trap density, Dit ≈ 1 × 108 cm−2 eV−1), reduces the recombination of the carriers. The start of a small number of transports by pinholes improves the fill factor (FF) up to 83%, reduces the series resistance (Rs) up to 0.5 Ω cm2, and also improves the power conversion efficiency (PEC) by up to 27.4%. The TOPCon with a modified nc-SiOx exhibits a dominant open circuit voltage (Voc) of 761 mV with a supreme FF of 83%. Our simulation provides an excellent match with the experimental results and supports excellent passivation properties. Overall, our study proposed an ameliorated knowledge about tunnel oxide, doping in the nc-SiOx layer, and additionally about the surface recombination velocity (SRV) impact on TOPCon solar cells.

High Interfacial-Energy and Lithiophilic Janus Interphase Enables Stable Lithium Metal Anodes.

The stability of solid electrolyte interphase (SEI) layers is critical for developing lithium (Li) metal batteries. However, the fabrication of stable SEI layers is plagued by un-controlled structures, properties, and functions. Here a controllable design of an ordered LiF-rich and lithiophilic hybrid Janus interphase (LiF-HJI) is reported using organic fluorination reagent as a functional SEI precursor. The LiF-HJI with a lower crystalline LiF layer and an upper Li organosulfide layer provides high interfacial energy with the Li metal and strong Li-ion affinity, allows homogenous Li-ion distribution, fast and uniform Li-ion transport, and excellent mechanical and passivation properties, enabling stable Li metal anodes under harsh conditions, such as high deposition capacities (6mAhcm-2 ), current densities (10mAcm-2 ), and rates (5 C). Stable LiF-HJI@Li greatly improves cycling stability and capacity retention (80.1% after 300 cycles) of Li||LiNi0.8 Co0.1 Mn0.1 O2 cells at a commercial-level areal capacity (≈4.2mAhcm-2 ). Even under a lean-electrolyte condition of 3gAh-1 , 80% capacity retention can be maintained after 100 cycles, demonstrating excellent cycling performance under such harsh conditions.

Tailored polymer coatings as corrosion inhibitor for mild steel in acid medium

Poly(o-bromophenol-co-N-methylaniline) [poly(OBP-co-NMA)] was electropolymerized in an acidic medium at 30°C under inert atmosphere. The formed polymer was characterized using IR spectroscopy, XRD, SEM and TGA analysis. The efficiency of the deposited polymer as a corrosion protection coating on a mild steel electrode in an acidic medium was investigated. Corrosion and impedance measurements reveal that the prepared polymer has excellent passivation properties. The free energy of adsorption of the prepared polymer on the electrode surface was in the range of ≈ − 19.5 kJ mol−1, which reveals a physical adsorption of the inhibitor molecules on the metallic surface.

A universal polymer shell-isolated nanoparticle (SHIN) design for single particle spectro-electrochemical SERS sensing using different core shapes.

Shell-isolated nanoparticles (SHINs) have attracted increasing interest for non-interfering plasmonic enhanced sensing in fields such as materials science, biosensing, and in various electrochemical systems. The metallic core of these nanoparticles is isolated from the surrounding environment preventing direct contact or chemical interaction with the metal surface, while still being close enough to enable localized surface plasmon enhancement of the Raman scattering signal from the analyte. This concept forms the basis of the shell isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) technique. To date, the vast majority of SHIN designs have focused on SiO2 shells around spherical nanoparticle cores and there has been very limited published research considering alternatives. In this article, we introduce a new polymer-based approach which provides excellent control over the layer thickness and can be applied to plasmonic metal nanoparticles of various shapes and sizes without compromising the overall nanoparticle morphology. The SHIN layers are shown to exhibit excellent passivation properties and robustness in the case of gold nanosphere (AuNP) and anisotropic gold nanostar (AuNS) core shapes. In addition, in situ SHINERS spectro-electrochemistry measurements performed on both SHIN and bare Au nanoparticles demonstrate the utility of the SHIN coatings. Correlated confocal Raman and SEM mapping was achieved to clearly establish single nanoparticle SERS sensitivity. Finally, confocal in situ SERS mapping enabled visualisation of the redox related molecular structure changes occurring on an electrode surface in the vicinity of individual SHIN-coated nanoparticles.

Ultra-thin passivation layers in Cu(In,Ga)Se2 thin-film solar cells: full-area passivated front contacts and their impact on bulk doping

In the search for highly transparent and non-toxic alternative front layers replacing state-of-the-art CdS in Cu(In,Ga)Se2 thin-film solar cells, alternatives rarely exceed reference devices in terms of efficiency. Full-area ultra-thin aluminium oxide tunnelling layers do not require any contact patterning and thus overcome the main drawback of insulating passivation layers. Even a few monolayers of aluminium oxide can be deposited in a controlled manner by atomic layer deposition, they show excellent interface passivation properties, low absorption, and suitable current transport characteristics on test devices. Depositing a ZnO-based transparent front contact, however, results in extremely poor solar cell performance. The issue is not necessarily a low quality of the alternative front layer, but rather the intricate relation between front layer processing and electronic bulk properties in the absorber layer. We identify three challenges critical for the development of novel front passivation approaches: (i) both Cd and Zn impurities beneficially reduce the high native net dopant concentration in the space charge region, (ii) sputter deposition of ZnO damages the passivation layer resulting in increased interface recombination, (iii) thermal treatments of devices with ZnO layer result in substantial Zn diffusion, which can penetrate the full absorber thickness already at moderate temperatures.

Development of thin polysilicon layers for application in monoPoly™ cells with screen-printed and fired metallization

Passivating contacts are an important technological innovation for crystalline silicon (c-Si) solar cells that can deliver efficiencies of over 24% in mass production. In this study, we comprehensively analyze n-type bifacial c-Si solar cells with rear side SiOx/phosphorus-doped (n+) poly-Si passivating contacts (monoPoly™ cells) with varying thicknesses (50–250 nm) of the n+ poly-Si layer. The poly-Si layers are deposited by low-pressure chemical vapor deposition (LPCVD) and then phosphorus doped ex-situ in a diffusion furnace. The ex-situ doping is carefully optimized for each individual thickness to achieve a step-function-like doping profile. Excellent passivation properties are achieved with the SiOx/n+ poly-Si stack, with a dark saturation current density of only 1 fA/cm2 for 150 nm n+ poly-Si layers. Metallization is realized by screen printing using commercially available fire-through pastes. Very low dark saturation current densities of <50 fA/cm2 are achieved under the metal contacts for n+ poly-Si thicknesses ≥100 nm. Trade-offs in the cells’ current-voltage (I–V) parameters are analyzed as a function of n+ poly-Si thickness and efficiency limiting factors are identified for cells with 50 nm n+ poly-Si layers.