poly-Si Layer Research Articles

Hydrogenation by catalytically generated atomic hydrogen for passivating contacts in crystalline silicon solar cells

Hydrogenation employing catalytically generated atomic hydrogen (Cat-H) is implemented on stacks of n-type polycrystalline silicon (poly-Si)/Si oxide (SiOx) to enhance passivation quality. The utilization of Cat-H demonstrates a substantial enhancement in surface passivation quality on crystalline Si (c-Si), resulting in an increase of the effective minority carrier lifetime (τeff) from 2.0 to 3.9 ms. The investigation reveals a dependency of τeff on the duration of Cat-H treatment: an initial rise followed by a plateau or slight decline. Secondary ion mass spectrometry (SIMS) measurements revealed the diffusion of H atoms into poly-Si and c-Si, which accumulate at the poly-Si/c-Si interface. This accumulation terminates dangling bonds in the poly-Si layer on the c-Si surface. Furthermore, the presence of an ultra-thin thermal Si oxide layer on the poly-Si layer formed during high-temperature annealing is crucial for protecting the film against etching induced by Cat-H.

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.

Effects on Metallization of n+-Poly-Si Layer for N-Type Tunnel Oxide Passivated Contact Solar Cells.

Thin polysilicon (poly-Si)-based passivating contacts can reduce parasitic absorption and the cost of n-TOPCon solar cells. Herein, n+-poly-Si layers with thicknesses of 30~100 nm were fabricated by low-pressure chemical vapor deposition (LPCVD) to create passivating contacts. We investigated the effect of n+-poly-Si layer thickness on the microstructure of the metallization contact formation, passivation, and electronic performance of n-TOPCon solar cells. The thickness of the poly-Si layer significantly affected the passivation of metallization-induced recombination under the metal contact (J0,metal) and the contact resistivity (ρc) of the cells. However, it had a minimal impact on the short-circuit current density (Jsc), which was primarily associated with corroded silver (Ag) at depths of the n+-poly-Si layer exceeding 40 nm. We introduced a thin n+-poly-Si layer with a thickness of 70 nm and a surface concentration of 5 × 1020 atoms/cm3. This layer can meet the requirements for low J0,metal and ρc values, leading to an increase in conversion efficiency of 25.65%. This optimized process of depositing a phosphorus-doped poly-Si layer can be commercially applied in photovoltaics to reduce processing times and lower costs.

Formation of one-dimensionally self-aligned Si-QDs and their local electron discharging properties

Self-aligned Si-quantum-dots (Si-QDs) with an areal density as high as ∼1011 cm−2 have been fabricated on ultrathin SiO2 by using a ∼4.5 nm thick poly-Si on insulator (SOI) substrate, and controlling low-pressure CVD using monosilane (SiH4), and followed by thermal oxidation. By controlling the thermal oxidation processes of Si-QDs and the poly-Si layer, we have successfully demonstrated the vertical alignment of Si-QDs, where the Si-QDs are also used as a shadow mask of the underlying poly-Si layer. We also demonstrated in-plane alignment of the one-dimensionally self-aligned Si-QDs on line-patterned SiO2. In addition, from surface potential measurements by using atomic force microscopy/Kelvin probe force microscopy, we confirmed that the initial surface potential change caused by valence electron extraction from the dots to the tip was stably maintained until ∼120 min, implying the quantum confinement effect at discrete energy levels of the upper and lower-QDs.

Structure and RF performance evolution of polycrystalline silicon charge capture layer for advanced RF-SOI in in-situ annealing process

In this paper, the structures and radio-frequency (RF) properties of high resistivity silicon (HR-Si) wafers with a polycrystalline silicon (Poly-Si) charge capture layer after in-situ annealing were investigated. The thermal treatment significantly improves the wafer warpage and optimize the resistivity of Poly-Si/HR-Si interfaces. By using spreading resistance profiling (SRP), energy dispersive spectrometer (EDS) and secondary ion mass spectrometry (SIMS) technology, the rise of interfacial resistivity may be as results of the pyrolysis of the native oxide and the diffusion of hydrogen atoms. The transmission Kikuchi diffraction (TKD) analysis exhibited that the grains were recrystallized during the annealing, leading to the transformation from the small angle boundaries (SAGBs) into low-Σ coincidence lattice grain boundaries (CSL GBs). The drop of the bulk resistivity of the Poly-Si layer is attributed to the reduction of the total grain boundary (GB) density and the increase of the low electro-activity GB density. Moreover, the microwave losses and non-linearity of the RF-SOI with embedded Poly-Si layer was evaluated by on-chip testing based on CPW. It was determined that the decrease in the Poly-Si resistivity only worsens the microwave losses but not the non-linearity.

InGaAs/Si PIN photodetector with low interfacial recombination rates realized by wafer bonding with a polycrystalline Si interlayer

In this Letter, we proposed a robust InGaAs/Si bonded heterojunction by polycrystalline Si (poly-Si) and amorphous interlayers. The ultra-thin amorphous layer is induced through Ar plasma treatment. The synergism of poly-Si and amorphous interlayers effectively blocks the lattice mismatch and releases the interfacial thermal stress. A bubble- and defect-free bonding interface is achieved even if after annealing at 500 °C, demonstrating compatibility with high-temperature processes. The heavily doped poly-Si interlayer sweeps the electric field from the poly-Si layer and concentrates in the amorphous layer, rendering electron tunneling through the bonding interface and reducing the interfacial recombination rates. As a result, the bonded InGaAs/Si PIN photodetector harvests a saturated and low dark density of 0.26 mA/cm2 at −1 V and a high rectification ratio of 3.5 × 105 at ±1 V. Additionally, the non-optimized device achieves a high responsivity of 0.82 A/W at 1550 nm. These results indicate that the proposed bonding strategy provides a viable route to tackle the electronic, optical, and thermal barriers of integrating single-crystal InGaAs into Si platforms. This enables the photodetection of InGaAs/Si devices with a high signal-to-noise ratio.

Three-Step Process for Efficient Solar Cells with Boron-Doped Passivated Contacts

Crystalline silicon (c-Si) solar cells with passivation stacks consisting of a polycrystalline silicon (poly-Si) layer and a thin interfacial silicon dioxide (SiO2) layer show high conversion efficiencies. Since the poly-Si layer in this structure acts as a carrier transport layer, high doping of the poly-Si layer is crucial for high conductivity and the efficient transport of charge carriers from the bulk to a metal contact. In this respect, conventional furnace-based high-temperature doping methods are limited by the solid solubility of the dopants in silicon. This limitation particularly affects p-type doping using boron. Previously, we showed that laser activation overcomes this limitation by melting the poly-Si layer, resulting in an active concentration beyond the solubility limit after crystallization. High electrically active boron concentrations ensure low contact resistivity at the (contact) metal/semiconductor interface and allow for the maskless patterning of the poly-Si layer by providing an etch-stop layer in an alkaline solution. However, the high doping concentration degrades during long high-temperature annealing steps. Here, we performed a test of the stability of such a high doping concentration under thermal stress. The active boron concentration shows only a minor reduction during SiNx:H deposition at a moderate temperature and a fast-firing step at a high temperature and with a short exposure time. However, for an annealing time tanneal = 30 min and an annealing temperature 600 °C ≤ Tanneal≤ 1000 °C, the high conductivity is significantly reduced, whereas a high passivation quality requires annealing in this range. We resolve this dilemma by introducing a second, healing laser reactivation step, which re-establishes the original high conductivity of the boron-doped poly-Si and does not degrade the passivation. After a thermal annealing temperature Tanneal = 985 °C, the reactivated layers show high sheet conductance (Gsh) with Gsh = 24 mS sq and high passivation quality, with the implied open-circuit voltage (iVOC) reaching iVOC = 715 mV. Therefore, our novel three-step process consisting of laser activation, thermal annealing, and laser reactivation/healing is suitable for fabricating highly efficient solar cells with p++-poly-Si/SiO2 contact passivation layers.

Investigation of Contact Resistivities on APCVD (p) Poly-Si for Fired Passivating Contacts

We investigate the properties of boron doped polycrystalline Si (poly-Si) deposited by atmospheric pressure chemical vapor deposition (APCVD) applied to fired passivating contacts (FPC), where no high temperature annealing takes place apart from the contact firing step. X-ray diffraction measurements show that the APCVD poly-Si is already partially crystallized directly after deposition and the crystallite size further increases during firing. Without metallization an implied open circuit voltage of up to 719 mV is achieved. Screen-printing with an Ag paste yields minimal contact resistivities of down to 1 mΩcm² at high firing temperatures. Furthermore, thicker poly-Si layers, accomplished by driving the same wafer multiple times through the APCVD system, generally correspond to lower contact resistivities for the FPC. This can partly be explained by an increasing crystallinity and conductivity during deposition due to the higher thermal budget during deposition for thicker layers as well as by a larger contact area for thicker poly-Si layers. Scanning electron microscopy on sample cross-sections show that almost the entire poly-Si layer is covered with Ag crystallites at high firing temperatures. For lower temperatures a lower density of Ag crystallites in the poly-Si is visible. Both findings hold for planar and textured surfaces.

Key Aspects of p-Type TOPCon on Textured Surface for Silicon Bottom Cells in Tandem Devices

Both-sides TOPCon solar cells are an interesting candidate for a highly efficient and thermally robust Silicon (Si) bottom cell for tandem devices, such as Perovskite-Si solar cells. However, preparation of p-type TOPCon on a textured surface is necessary which is particularly challenging. This work aims to gain a deeper understanding of the limiting factors and thereby optimize the SiOx/poly-Si(p) contact to close the gap to its n-type counterpart. Using symmetrical lifetime samples, we first show that a high level of surface passivation can be achieved using thermally grown interfacial oxides of different thicknesses. The samples strongly benefit from an effective thermal activation of hydrogenation by means of fast-firing. Thus, a recombination current density J0s as low as 23.4 fA/cm² was achieved for p-type TOPCon on textured surface featuring an in situ Boron-doped poly-Si layer prepared by plasma enhanced chemical vapor deposition (PECVD). Moreover, we show that the passivation quality strongly depends on surface morphology. Smoothening the random pyramids’ valleys and – what is more – the tips has a positive impact on the surface passivation.

Wet chemical poly-Si(n) wrap-around removal for TOPCon solar cells

This work gives an overview on different technological solutions for polysilicon removal in industrial tunnel oxide passivated contact (i-TOPCon) n-type silicon solar cell fabrication. The removal of parasitically deposited poly-Si layers on the front and the edges is a mandatory requirement for a low reverse bias junction leakage current (Irev). A polysilicon removal study on wafer level shows (i) that the efficient removal of the surface oxide layer before poly-Si etching is crucial to achieve short etching times and (ii) that an additive in the KOH solution enhances etching selectivity between poly-Si and silicon oxide surfaces. To evaluate the impact on device level, TOPCon cells have been fabricated in parallel using in-situ n-doped PECVD and LPCVD layers, as well as ex-situ LPCVD poly-Si layers, with another variation of poly-Si removal processes, namely wet chemical inline, wet chemical batch cluster and atmospheric dry etching (ADE). Our results show that a two-minute inline polysilicon removal in hot KOH meets the Irev qualification in case of as deposited in-situ doped layers, whereas for ex-situ doped layers a batch process with a five-minute KOH etching time is needed. LPCVD poly-Si cells show efficiencies above 23%, PECVD poly-Si cells with a batch cluster poly-Si removal process up to 23.4%.

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.

Characterization of solar cell passivating contacts using time-of-flight elastic recoil detection analysis

The unambiguous detection of hydrogen in solar cell contact structures is critical to understanding passivation and degradation phenomena. Deuterium is often used to depict the distribution of hydrogen more clearly. However, experimental noise and artifacts can hinder the clear identification of species. This work provides a report of time-of-flight elastic recoil detection (ToF-ERD) analysis to identify H/D contents in a thin poly-Si/SiOx passivating contact. The structure contained a 1.3 nm interfacial SiOx and an n+ doped poly-Si layer with a partly deuterated SiNx coating. The samples were annealed to release H/D, and ToF-ERD was used to detect H/D in monatomic, singly charged forms, without the detection artifacts associated with conventional secondary ion mass spectroscopy. Chlorine ions were used to recoil surface species, which were analyzed to clearly and unambiguously resolve H and D. Depth profiles for the recoiled Si, N, O, D, and H atoms were calculated from the energy and velocity information registered after scattering events, which enabled the analysis of the structure of the multilayer stack. Even though the surface roughness and experimental limitations cause visible broadening of the profiles, which can hinder clear detection at the interfacial oxide, the ability to resolve hydrogen-related species makes ToF-ERD a significant and promising tool for studying the role of hydrogen in the performance and degradation of solar cell passivating contacts.

Paste-based silver reduction for iTOPCon rear side metallization

This work presents two approaches to reduce the silver (Ag) amount on the rear side of M2-sized industrial tunnel oxide passivated contact (iTOPCon) solar cells by (partially) substituting conventional Ag pastes with copper (Cu) and aluminum (Al) pastes. The first approach is Cu-based and works by screen printing an Ag layer with ca. 75% Ag paste reduction compared to a conventional Ag layer (functioning as a contact and Cu barrier layer) and screen printing a full-area Cu layer on top of the Ag layer (functioning as a conduction layer compensating the reduced Ag amount). This Cu-based approach yields similar power conversion efficiency (η) compared to the conventional approach, showing the Cu-based approach is promising for iTOPCon solar cells. The second approach is Al-based and works by laser contact opening of the dielectric layers and screen printing a full-area layer with an Al paste – adapted to properly contact an n+-poly-Si layer –, substituting Ag on the rear side entirely. This Al-based approach exhibits a 0.9%absη gap to the conventional approach, mainly stemming from the Al paste damaging the poly-Si layer, while – on a positive note – neither rear p+ layer formation nor tunnel oxide layer penetration by the Al paste is detected. Even though the abovementioned η gap must be eliminated in the future, it shows the principal functionality and potential of such type of contact for iTOPCon solar cells.

Soft deposition of TCOs by pulsed laser for high-quality ultra-thin poly-Si passivating contacts

In this work, the applicability of pulsed laser deposition (PLD) of transparent conductive oxides (TCOs) on high-quality ultra-thin poly-Si based passivating contacts is explored. Parasitic absorption caused by poly-Si layers can be minimized by reducing the poly-Si layer thickness. However, TCO deposition on poly-Si contacts, commonly by sputtering, results in severe deposition-induced damage and further aggravates the surface passivation for thinner poly-Si layers (<20 nm). Although a thermal treatment at elevated temperature (∼350 °C) can be used to partially repair the surface passivation quality, the contact resistivity severely increases due to the formation of a parasitic oxide layer at the poly-Si/ITO interface. Alternatively, we show that PLD TCOs can be used to mitigate the damage on ultra-thin (∼10 nm) poly-Si layers. Further improvement in poly-Si contact passivation can be achieved by increasing the deposition pressure while low contact resistivities (∼45 mΩ cm2) and good thermal stability (up to 350 °C) are achieved with a PLD indium-doped tin oxide (ITO) layer on high-quality ultra-thin poly-Si(n+) contacts. This allows for the application of a highly transparent front side contact by combining the excellent opto-electrical properties of a PLD ITO film with a 10 nm thin poly-Si contact.

Theoretical analysis of backside polycrystalline silicon layer in the TOPCon solar cells

As an upgraded version of passivated emitter and rear cell (PERC) solar cells, the performance of tunnel oxide passivating contacts (TOPCon) solar cells is very dependent on the silicon oxide layer and poly-Si layer. We found that different crystallization rates or doping of germanium, carbon and other elements in poly-Si can change the band gap of poly-Si, which has an impact on the efficiency (Eff) of TOPCon solar cells. Therefore, the appropriate band gap is particularly important. At the same time, the internal defect of poly-Si also have great influence on the performance of solar cells. The simulated band diagram, charge carrier concentration and recombination rate were used to deeply explore the defect in poly-Si and the influence of poly-Si with different band gap on the performance of TOPCon solar cells.

Unlocking the full potential of monolithic perovskite/biPoly™ Si tandem devices through in-depth analysis and detailed engineering

Perovskite/Si tandem solar cells have emerged as one highly promising tandem configuration of tandem devices for 1-Sun photovoltaic systems. Up to now, heterojunction (HJ) cells have been the dominant silicon bottom cell structure and holds the record efficiency of dual-junction perovskite/Si tandem cells, whereas the investigation on perovskite/Si tandem cells using Si bottom cells that dominate today's mass markets (such as PERC and TOPCon) is still limited. In this work, we delve into the crucial optical and electrical engineering aspects required for perovskite/Si devices based on bifacial TOPCon structures (biPoly™), which has high efficiency potential as a single-junction Si cell, enables TCO-free contacts and is expected to be compatible with current mass production technologies. Simulations predict that such devices can potentially achieve a current density of 20.4 mA/cm2 despite of the parasitic absorption in poly-Si layers, comparable to that of HJ-based perovskite-Si tandem devices. We also demonstrate through simulations that edge and peripheral recombination effects can be mitigated by selecting an appropriate substrate size and employing locally doped poly-Si layers. Such improvements are also preliminarily verified with a prototype device. By carefully designing device structures and advancing fabrication techniques, perovskite/biPoly™ Si tandem cells can come closer to realizing the full potential of biPoly™ cells and achieve efficiencies comparable to those observed in devices utilizing HJ cells.

Fundamental microscopic studies on the etching behavior of silver pastes on poly-Si/SiOx passivating contacts

Screen printing of Ag paste is a key process for implementing polycrystalline-silicon/silicon oxide (poly-Si/SiOx) passivating contacts in industrial solar cells. Thereby, the formation of Ag crystallites on the Si surface is crucial for a low-ohmic contact. Recently, it has been observed that Ag crystallites are predominantly formed within the poly-Si layer and stop at the thermal SiOx, thermal interface, causing a cuboidal shape. To avoid a direct contact of the Ag crystallites with the underlying SiOx, thermal/crystalline-Si (c-Si) interface, a multilayer approach with interlayer SiOx, inter between several poly-Si layers is presented. A stack of three 50 nm poly-Si layers achieves highest cell potential. Further, the metallization process parameters are scanned to check when this cuboidal Ag crystallite shape occurs. While different amorphous-silicon (a-Si) deposition techniques show no changes, there are strong indications that the glass frit etching is responsible for a different etching mechanism causing the breakdown of the SiOx stop.

Thermal interdiffusion, microstructure and contact resistivity of NiOx/Ni/p+ poly-Si layer systems for perovskite/TOPCon tandem solar cells during annealing processes

In a recently published article (Lange et al., 2023) [1], we envisioned and discussed a tandem solar cell concept based on a perovskite/TOPCon architecture in p-i-n configuration, that utilizes a p+/n+ polycrystalline silicon (poly-Si) tunnel junction and NiOx as hole transport material of the perovskite top cell. A direct contact of NiOx to p+ poly-Si is inevitable in such a device. We investigated that junction and reported how the contact resistivity of the NiOx/p+ poly-Si junction can be improved by orders of magnitudes by intentionally inserting a nm-thin metallic Ni interlayer at that interface through the formation of nickel silicide.In this contribution, we present comprehensive data on layer stack morphology, composition and interdiffusion and the impact on the measured contact resistivity based on (scanning) transmission electron microscopy (STEM) coupled with energy-dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) of model samples as well as the real contact structures. Diffusion and reaction processes in the NiOx/Ni/p+ poly-Si layer stack are investigated during the annealing in the temperature range between 100 °C and 500 °C for varying Ni interlayer thicknesses of 0, 1.0 and 2.0 nm. Furthermore, two NiOx syntheses routes are investigated: sputter deposition (s-NiOx) and a wet-chemical approach (wc-NiOx). We correlate the improvement of contact resistivity for both systems and temperatures <300 °C in regard to contacts without metallic Ni interlayer with the observation of pinhole formation within the SiOz. We have observed that annealing the Ag/s-NiOx junctions above 300 °C under ambient air leads to rectifying contacts and high contact resistivities due to excessive interdiffusion of Ni, O and Ag.

Study on the fundamental factors of the property evolution of a 300 mm polycrystalline trap-rich layer

The geometry and resistivity of the trap-rich layer are key parameters for 300 mm trap-rich silicon-on-insulator (TR-SOI) wafers. In this paper, the evolution of the warpage and resistivity of poly-Si layers grown by atmospheric chemical vapor deposition with deposition temperature has been studied. The ability to quantify the surface grain size of undoped poly-Si was evaluated using scanning electron microscopy, electron backscattering diffraction, and transmission Kikuchi diffraction (TKD). With a resolution scale of several nanometers, the fine grains on the surface of poly-Si are accurately identified by TKD. It is confirmed that the decrease in compressive stress with deposition temperature is caused by the lower ratio of (110) grain orientation and the reduction of fine grains on the surface. However, when stress is released, the random grain boundaries (GBs) of poly-Si change into coincidence site lattice low-Σ GBs with low recombination activity, which greatly lowers the film bulk resistivity and reduces its capacity to trap charges. Thus, a process window for the manufacturing of 300 mm TR-SOI wafers is created by balancing the degradation of resistivity in the process of using deposition temperature to seek improvements in poly-Si warpage.

Laser Activation for Highly Boron-Doped Passivated Contacts

Passivated, selective contacts in silicon solar cells consist of a double layer of highly doped polycrystalline silicon (poly Si) and thin interfacial silicon dioxide (SiO2). This design concept allows for the highest efficiencies. Here, we report on a selective laser activation process, resulting in highly doped p++-type poly Si on top of the SiO2. In this double-layer structure, the p++-poly Si layer serves as a layer for transporting the generated holes from the bulk to a metal contact and, therefore, needs to be highly conductive for holes. High boron-doping of the poly Si layers is one approach to establish the desired high conductivity. In a laser activation step, a laser pulse melts the poly Si layer, and subsequent rapid cooling of the Si melt enables electrically active boron concentrations exceeding the solid solubility limit. In addition to the high conductivity, the high active boron concentration in the poly Si layer allows maskless patterning of p++-poly Si/SiO2 layers by providing an etch stop layer in the Si etchant solution, which results in a locally structured p++-poly Si/SiO2 after the etching process. The challenge in the laser activation technique is not to destroy the thin SiO2, which necessitates fine tuning of the laser process. In order to find the optimal processing window, we test laser pulse energy densities (Hp) in a broad range of 0.7 J/cm2 ≤ Hp ≤ 5 J/cm2 on poly Si layers with two different thicknesses dpoly Si,1 = 155 nm and dpoly Si,2 = 264 nm. Finally, the processing window 2.8 J/cm2≤ Hp ≤ 4 J/cm2 leads to the highest sheet conductance (Gsh) without destroying the SiO2 for both poly Si layer thicknesses. For both tested poly Si layers, the majority of the symmetric lifetime samples processed using these Hp achieve a good passivation quality with a high implied open circuit voltage (iVOC) and a low saturation current density (J0). The best sample achieves iVOC = 722 mV and J0 = 6.7 fA/cm2 per side. This low surface recombination current density, together with the accompanying measurements of the doping profiles, suggests that the SiO2 is not damaged during the laser process. We also observe that the passivation quality is independent of the tested poly Si layer thicknesses. The findings of this study show that laser-activated p++-poly Si/SiO2 are not only suitable for integration into advanced passivated contact solar cells, but also offer the possibility of maskless patterning of these stacks, substantially simplifying such solar cell production.