Nanocrystalline Silicon Oxide Research Articles

A Review: Application of Doped Hydrogenated Nanocrystalline Silicon Oxide in High Efficiency Solar Cell Devices.

Due to the unique microstructure of hydrogenated nanocrystalline silicon oxide (nc-SiOx:H), the optoelectronic properties of this material can be tuned over a wide range, which makes it adaptable to different solar cell applications. In this work, the authors review the material properties of nc-SiOx:H and the versatility of its applications in different types of solar cells. The review starts by introducing the growth principle of doped nc-SiOx:H layers, the effect of oxygen content on the material properties, and the relationship between optoelectronic properties and its microstructure. A theoretical analysis of charge carrier transport mechanisms in silicon heterojunction (SHJ) solar cells with wide band gap layers is then presented. Afterwards, the authors focus on the recent developments in the implementation of nc-SiOx:H and hydrogenated amorphous silicon oxide (a-SiOx:H) films for SHJ, passivating contacts, and perovskite/silicon tandem devices.

Synergetic Effect of Gas Compositions on Material Properties of n‐Type Nanocrystalline Silicon Oxide Prepared by Plasma‐Enhanced Chemical Vapor Deposition

Hydrogenated nanocrystalline silicon oxide (nc‐SiOx:H) has drawn extensive attention during the past years for the utilization of silicon heterojunction (SHJ) solar cells. This material is demonstrated to be the key to the performance improvement of SHJ solar cells. Herein, the influence of the process gas compositions on the optical, electronic, chemical, and structural properties of n‐type nc‐SiOx:H films at the thickness of 38 nm is systematically investigated. The synergetic effect of CO2 and PH3 gas flow fraction ( and ) and the synergetic effect of CO2 and SiH4 gas flow fraction ( and ) on the growth of nc‐SiOx:H (n) films are demonstrated. Creatively combining the Fourier‐transform infrared, UV‐Raman scattering spectroscopy, spectroscopy ellipsometry, and photo‐thermal deflection spectroscopy measurement, the mechanism behind the synergetic effect of the gas compositions on the material properties is analyzed.

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.

Highly conductive p-type nc-SiOX:H thin films deposited at 130°C via efficient incorporation of plasma synthesized silicon nanocrystals and their application in SHJ solar cells

We present highly conductive and transparent p-type hydrogenated nanocrystalline silicon oxide (p-type nc-SiOX:H) layers produced by Plasma Enhanced Chemical Vapor Deposition (PECVD) at 130°C and 150°C. We report on the crystalline volume fraction (XC), spectral broadening parameter C, and dark conductivity (σ) as functions of the growth temperature and RF power, and how these properties evolve with post-deposition annealing at 250°C and 300°C. Interestingly, we observe that the best layers in terms of crystalline volume fraction and conductivity are obtained at the lowest temperature and RF power, which we attribute to the soft landing of silicon nanocrystals synthesized in the plasma. The p-type nc-SiOX:H layers with the best properties on glass substrates are implemented as carrier-selective contacts in silicon heterojunction (SHJ) solar cells with the structure: (n) a-Si:H / (i) a-Si:H / n-type c-Si / (i) a-Si:H / (i) a-SiOX:H / (p) nc-SiOX:H / (p) nc-Si:H where all films are deposited by PECVD. The cells were completed with sputtered ITO on the front and rear sides plus Ag on the rear side, and Ag grid on the front, with the best devices showing conversion efficiencies of 21.8%, which, contrary to a-Si:H contact layers, are preserved or even slightly improved upon annealing at 240°C.

Improved interface microstructure between crystalline silicon and nanocrystalline silicon oxide window layer of silicon heterojunction solar cells

N-type hydrogenated nanocrystalline silicon oxide (nc-SiOx:H) is potential to enhance the performance of silicon heterojunction solar cells, but the raised plasma damage on underlying layer during the nc-SiOx:H deposition with a high-volume fraction of hydrogen is a burning issue. The underlying intrinsic hydrogenated amorphous silicon (i-a-Si:H) bilayer between n-type crystalline silicon (c-Si) and n-type nc-SiOx:H has been investigated by modulating silane (SiH4) gas flow rate (GFR) of interface porous layer. It has been found that the initial H-rich i-a-Si:H bilayer deposited by interfacial 1600 sccm GFR with relatively stable larger voids diameter and less voids number density can not only withstand hydrogen ions bombardment but also passivate c-Si surface well. Meanwhile, it also has been verified that the optimal n-seed deposition can further enhance both total hydrogen content and hydrogen content in compact structure to promote c-Si surface passivation and carrier transportation. The optimized SiH4 GFR for the interfacial i-a-Si:H growth and the appropriate deposition time of n-seed layer have been applied into the front passivation layer of silicon heterojunction solar cells, thus a high efficiency of approximate 25 % with high VOC and FF has been achieved.

A novel passivating contact approach for enhanced performance of crystalline silicon solar cells

Passivated contacts based on ultrathin silicon oxide (SiOx) layers and phosphorus-doped nanocrystalline silicon oxide (nc-SiOx(n)) layers have been examined for their application in tunnel oxide-passivated contact (TOPCon) solar cells. Passivated contact nc-SiOx(n)/SiOx, is accomplished by implementing a thermally grown SiOx tunnel layer and a plasma-enhanced chemical vapor deposited (PECVD)-grown nc-SiOx(n) layer, which are subsequently transformed into a more crystalline phase by annealing at a higher temperature. In this research, a 3.2 × 3.2 cm solar cell was fabricated, where the base material was n-type crystalline silicon (c-Si(n)), and an aluminum oxide (Al2O3) acts as a passivation layer which helps to enhanced the passivation properties and indium tin oxide (ITO) layer was used on the front side, which could serve as an anti-reflection coating (ARC), respectively. The influence of the temperature, doping level, and thickness of nc-SiOx(n) on the surface passivation of the contacts was investigated. Superior recombination current density (Jo) values of up to 2.9 fA/cm2 were assessed for the nc-SiOx(n)/SiOx contacts. TOPCon solar cells with top boron-doped emitter, Al2O3, and ITO/rear stack of nc-SiOx(n)/SiOx passivation contacts were formed and resulted in Voc = 650 mV and FF = 78%. Furthermore, we focused on ameliorating the achievements of solar cells using a transparent passivating contact-based nc-SiOx(n), as well as the passivation process and operating principle.

Achievement of 25.54% power conversion efficiency by optimization of current losses at the front side of silicon heterojunction solar cells

AbstractParasitic absorption in the front window layers of transparent conductive oxide (TCO) films and carrier selective collection layers and the optical shading losses from the metallic finger grid mainly limit the current generation in silicon heterojunction (SHJ) solar cells. In this work, we demonstrate an improved short‐circuit current density (Jsc) of 40.24 mA/cm2 through a combination of novel window layers composed of transition metal doped indium oxide (IMO) and hydrogenated nanocrystalline silicon oxide (nc‐SiOx:H) films and Cu plating for SHJ solar cells. By introducing water vapor during direct current (DC) magnetron sputtering deposition process, IMO films show a large optical band gap (Eg) of about 3.88 eV and high mobility up to 83.2 cm2/V·s, while maintaining a low carrier concentration, which leads to high transparency and low near‐infrared (NIR) free carrier absorption (FCA). In addition to its high deposition rate and crystalline volume fraction, we found that nc‐SiOx:H films deposited by very high frequency (VHF) excited plasma‐enhanced chemical vapor deposition (PECVD) show an excellent surface passivation quality, which not only improves the open circuit voltage (Voc) of SHJ cells but also increases the Jsc through improved carrier selective collection. The quantified Jsc breakdown analysis was performed to identify the room for improvement, and it showed that the front shading loss (about 1.32 mA/cm2) is the largest portion. By combining the benefits of these window layer enhancements with the further use of fine line width and conductivity of Cu plating, SHJ solar cells, with a Jsc improvement of 0.57 mA/cm2 and a certified efficiency of 25.54%, were achieved on a total area of 274.5 cm2 using in‐house pilot production line equipment.

In situ modulated photoluminescence study of the hydrogenation processes of tunnel oxide passivating contacts during plasma processes

AbstractCompared to current c‐Si solar cell technologies, fired passivating contacts (FPCs) can reduce the thermal budget of the solar cell fabrication process. In this study, a simplified process flow for the fabrication of these contacts is investigated along with the use of two hole transport materials: p‐type nanocrystalline silicon ((p) nc‐Si:H) and nanocrystalline silicon oxide ((p) nc‐SiOx:H). More specifically, the passivation properties provided by the FPC stack are assessed at different stages of the manufacturing. The hydrogenation process is studied using in situ modulated photoluminescence (MPL) which allows to measure in real time the effective minority carrier lifetime in the sample during a process step. The increase of passivation observed during the deposition of the capping silicon‐nitride (a‐SiNx:H) layer by plasma‐enhanced chemical vapor deposition is shown to be due to both annealing of the sample and the deposition in presence of silane in the plasma, while the exposure to an NH3 and H2 plasma is mostly detrimental for the passivation properties. The in situ MPL measurements additionally allow us to show that the improvement of the passivation properties happens during the first few minutes of a‐SiNx:H deposition.

Origin of photo-enhanced hysteretic electrical conductance in nanostructured silicon-based heterojunction

Photo-enhanced hysteretic I–V curves have been observed under reverse bias in a p-i-n structure containing electrochemically etched nanostructured silicon (Si) sandwiched between p-Si and n-type a-Si:H layers. These curves have been found to depend on intensity of incident illumination and structural morphology of the nanostructured Si layer. The conductance in trace path is lower than that in retrace path. Charge transport mechanism in this structure has been interpreted using microscopic description of charge trapping and detrapping in the defect states present at the interface of nanocrystalline silicon core and oxide shell in the active layer. An applied voltage dependent probability distribution of trapping and detrapping has been calculated in light of classical random walk problem. The trapping/detrapping of charges leading to development/destruction of potential barriers in the path of charge flow shows an analogy with the river bed deposition/erosion. The rate of trapping has been considered to depend on the empty defect states whereas the rate of detrapping depends on the already filled defects. Moreover, the rate of both trapping and detrapping is expected to depend on the charge flow rate. All these considerations lead the I–V relations for trace and retrace paths in reverse bias fitting nicely with experimental I–V loops. The observed peaks in the voltage dependent dynamic conductance in trace and retrace paths have been explained as a consequence of development and destruction of two barriers in the active layer for electrons and holes separately. Best fit values of the fitting parameters indicates that the trace path is dominated by holes whereas the retrace path is dominated by electronic transport. The difference in mobility of electron and hole leads to different trapping and detrapping rates in the two paths resulting in the observed hysteresis.

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 < 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.

N-type nc-SiOx:H film enables efficient and stable silicon heterojunction solar cells in sodium environment

Hydrogenated nanocrystalline silicon oxide (nc-SiOx:H) is promising to replace hydrogenated amorphous silicon (a-Si:H) as the window layer of silicon heterojunction (SHJ) solar cells due to its lower parasitic absorption at short wavelength. In this work, by varying the growth conditions of nc-SiOx:H, we prepared highly conductive, highly transparent phosphorus-doped nc-SiOx:H film, and successfully applied as the window layer of SHJ cells. The short-circuit current density gains 0.5 mA/cm2, together with an improvement of power conversion efficiency by 0.3%, whose average value reaches 24.09% on 6-inch total-area wafers. More importantly, we find these devices show better stability in sodium environment at 85 °C and 85% relative humidity.

High-efficiency hybrid solar cell with a nano-crystalline silicon oxide layer as an electron-selective contact

The efficiency of silicon heterojunction solar cells is limited by various factors including low surface passivation, parasitic absorption, and recombination losses. Herein, the surface passivation quality of crystalline silicon solar cells is improved by a hybrid passivation structure including a silicon heterojunction contact at the front side and a stack of tunneling oxide with n-type nano-crystalline silicon oxide (nc-SiOx(n)) passivating contact at the rear side. A passivation contact with thin silicon oxide (SiO2) and poly-silicon was previously proposed to enhance the rear surface passivation. In our study, the poly-silicon layer is swapped with the nc-SiOx(n) layer to improve the effective surface passivation, electrical properties, recombination losses, and carrier selectivity. The hybrid passivation structure shows significant passivation improvement with lifetime (τeff) of 2696 μs and implied open-circuit voltage (i-Voc) of 735 mV as compared with both-sides traditional silicon heterojunction (1650 μs, 719 mV) and tunneling passivation contact (2146 μs, 725 mV). The hybrid solar cell shows a potential performance as; open circuit voltage (Voc) = 724 mV, short circuit current (Jsc) = 38.95 mA/cm2, fill factor (FF) of 75.9%, efficiency (η) = 21.4%. However, there is room to further improve the overall cell performance.

Improvement in a-Si:H silicon solar cells with using double p-type window layers based on nanocrystalline silicon oxide

In this study, our objective was to analyze by simulation the effect of using two different double p-type layers, one p-type based on hydrogenated nanocrystalline silicon (nc-Si:H) and the other p-type based on hydrogenated nanocrystalline silicon oxide (nc-SiOx:H) on the performances of n-i-p a-Si:H based solar cell. The AMPS-1D computer code is used to realize the simulation. Two devices were simulated and compared, the first structure device is:metal/n-a-Si:H/i-a-Si:H/p-nc-SiOx:H/p+nc-SiOx:H/ITO and the second structure device is:metal/n-a-Si:H/i-a-Si:H/p-nc-Si:H/p+nc-Si:H/ITO. An improvements in the JSC in the case of structure with p nc-SiOx:H layers is mainly due to the good absorption in the short wavelength range which is causes by the presence of oxygen in the high band gap p-nc-SiOx:H layer and which makes it more transparent. This good light absorption leads to a high photocarriers generation which combined with a high doping concentration to extract holes from the active layer. The presence of the p-nc-SiOx:H buffer layer at the i/p-window interface reduces the recombination at this interface and improves the VOC. For the optimized window layer parameters values: NDG = NAG = 1017 cm−3, L = 15 nm, NA = 5 × 1019 cm−3 and with NA = 1018 cm−3 for the buffer layer, the best performances were obtained in the case of solar cell with double p-nc-SiOx:H type window layers (JSC = 13.80 mA/cm2, VOC = 934 mV, FF = 79.1% and Eff = 10.21%).

Improving passivation properties using a nano-crystalline silicon oxide layer for high-efficiency TOPCon cells

High conversion efficiency can achieve by superior surface passivation and material quality. In this study, a novel passivation contact structure based on nanocrystalline silicon oxide (nc-SiOx) films was investigated. Traditionally, poly silicon junctions in tunnel oxide passivated contact (TOPCon) solar cells possess exceptional junction characteristics, but current losses are noted due to their optical absorption if they are applied in solar cell devices. In this study, we replaced the poly-Si layer in TOPCon solar cells with nc-SiOx to enhance transparency. By employing the nc-SiOx layer, effective surface passivation, carrier selectivity, electrical properties and optical transmission can be used to improve, all are vitally important in devise operation. We optimized the deposited nc-SiOx layer on an ultra-thin (~1.5 nm) silicon dioxide (SiO2) tunnel oxide layer to improve recombination current density and carrier lifetime. The passivation characteristics were improved by varying the annealing temperature and thickness of the nc-SiOx layer. The 50 nm thick nc-SiOx layer was capable of yielding a high implied open-circuit voltage (i-Voc) of 739 mV and low contact resistivity (ρ) of 14.2 (mΩ/cm2) in addition to a low depleted recombination current density (Jo) of 1.1 fA/cm2 with a post-deposition annealing temperature up to 950 °C. Improved passivation characteristics are the result of a more prominent annealing temperature. Our proposed technique has immense potential for achieving higher efficiency for fabricating various structures of TOPCon solar cells. As per AFORST Het simulation results by using nc-SiOx for TOPCon structure, we got Voc of 761.5 mV, Jsc of 43.5 mA/cm2, FF of 83%, and η of 27.49%, respectively.

Band-offset reduction for effective hole carrier collection in bifacial silicon heterojunction solar cells

Bifacial silicon heterojunction (SHJ) solar cells are gaining popularity owing to their potential for high performance. To achieve bifacial illumination, wide-gap hydrogenated nanocrystalline silicon oxide (nc-SiOx:H) materials are used as front and rear surface fields, which significantly enhance the light absorbed into the cells. In this study, we reduced the band offset at the p/i interface of bifacial SHJ solar cells using an ultra-thin buffer layer of hydrogenated amorphous silicon oxide (a-SiOx:H) to increase the efficiency of hole carrier transport and collection. Effectively, we were able to enhance the open-circuit voltage (Voc) and fill factor (FF) by 0.97% and 9.59%, respectively. These results were confirmed through experimental procedures and simulations. Subsequently, the experimental efficiency with respect to the bifacial illumination of a rear emitter silicon heterojunction solar cell was increased by 23.6%, with a Voc of 729 mV, FF of 80%, and short-circuit current density of 40.5 mA/cm2.

Bifunctional CO2 Plasma Treatment at the i/p Interface Enhancing the Performance of Planar Silicon Heterojunction Solar Cells

Hydrogenated nanocrystalline silicon (nc‐Si:H) or hydrogenated nanocrystalline silicon oxide (nc‐SiOx:H) as window layers have ample potential to improve the short‐circuit current density (JSC) of silicon heterojunction (SHJ) solar cells due to their wide optical bandgap. However, the growth of their nanocrystals within a 20 nm‐thickness on intrinsic hydrogenated amorphous silicon (i‐a‐Si:H) poses a challenge. Plasma treatment (PT) after i‐a‐Si:H deposition is usually used to improve passivation performance. Herein, the i/p interface is subjected to CO2 PT: a 20 s post CO2 PT is proven to be beneficial in obtaining improved passivation performance. This can be achieved by activated hydrogen which can be diffused to the wafer surface and can saturate the dangling bonds on it. Extending the CO2 PT time from 20 to 40 s, the oxygen (O) insertion into i‐a‐Si:H starts to increase slowly, which leads to marginal change of microstructure in the p layer. Strained SiSi bonds by oxygen incorporation into the a‐Si:H network generate nucleation sites and consequently accelerate the nucleation of p‐nc‐Si:H on i‐a‐Si:H. Finally, it is demonstrated that the power conversion efficiency (PCE) of planar SHJ solar cells is enhanced from 12.65% to 19.06% by a 20 s CO2 PT at the i/p interface.

Low-temperature synthesis of conducting boron-doped nanocrystalline silicon oxide thin films as the window layer of solar cells

Low-temperature synthesis of highly transparent conducting B-doped (p-type) nc-SiOX:H films has been pursued by 13.56 MHz plasma-CVD, using a combination of SiH4, CO2 and B2H6, diluted by H2 and He. Higher substrate temperature (TS) encourages nanocrystallization in B-doped nc-SiOX:H network by reducing bonded H-content, while bonded O-content also reduces simultaneously. At optimized TS = 150 °C, p–nc-SiOX:H film having an optical band gap ~1.98 eV, high conductivity ~0.18 S cm−1, has been obtained via dopant-induced escalation of the electrically active carriers at a deposition rate ~5.3 nm/min. The p–nc-SiOX:H film appears as a promising window layer for the top sub-cell of multi-junction silicon solar cells. A single-junction nc-Si:H based p-i-n solar cell of efficiency (η) ~7.14% with a current-density (JSC) ~14.18 mA/cm2, reasonable fill-factor (FF) ~66.2% and open-circuit voltage (VOC) ~0.7606 V has been fabricated, using the optimum p-type nc-SiOX:H as the window layer deposited at TS = 150 °C.

Synergistic effect of CO2 and PH3 on the properties of n-type nanocrystalline silicon oxide prepared by plasma-enhanced chemical vapor deposition

Synergistic effect of CO2 and PH3 on the properties of n-type nanocrystalline silicon oxide prepared by plasma-enhanced chemical vapor deposition

Fabrication of wide-gap p-type microcrystalline silicon-oxide emitter induced high built-in potential in heterojunction solar cells

We have investigated a heterojunction intrinsic thin-layer (HIT) solar cell with a boron-doped hydrogenated nanocrystalline silicon-oxide emitter layer. First, we researched the band-gap engineering of boron (B2H6)-doped wide-gap hydrogenated nanocrystalline silicon-oxide (p-type nc-SiO:H) films with good electrical properties in terms of the dark conductivity and the activation energy. The films prepared at lower doping ratios and higher hydrogen dilution ratios showed higher optical gaps (Eopt) with high horizontal (σd,//) or vertical dark conductivities (σd,⊥) and lower activation energies (Ea). Notably, all p-type nc-SiO:H films had better properties than boron-doped amorphous silicon (a-Si:H) films. We controlled Eopt from 2.13 to 2.33 eV with σd,// from 1.53 × 10−2 to 9.59 × 10−3 S/cm and with σd,⊥ from 4.56 × 10−7 to 2.53 × 10−8 S/cm; as well as Ea from 0.091 to 0.113 eV. Second, we showed a remarkable increase in the built-in potential by applying p-type nc-SiO:H films to HIT solar cells. The solar cell properties showed 4.05%, 6.02%, and 8.67% increases in the open-circuit voltage, fill factor, and efficiency, respectively, when a p-type nc-SiO:H emitter layer had been applied between the In2O3:Sn and the i-type a-Si:H layer. The mechanism of improvement is discussed using a methodical approach to the interfacial properties.

Design and optimization of hole collectors based on nc-SiOx:H for high-efficiency silicon heterojunction solar cells

Low activation energy (Ea) and wide bandgap (Eg) are essential for (p)-contacts to achieve effective hole collection in silicon heterojunction (SHJ) solar cells. In this work, we study Plasma-Enhanced Chemical Vapor Deposition p-type hydrogenated nanocrystalline silicon oxide, (p)nc-SiOx:H, combined with (p)nc-Si:H as (p)-contact in front/back-contacted SHJ solar cells. We firstly determine the effect of a plasma treatment at the (i)a-Si:H/(p)-contact interface on the thickness-dependent Ea of (p)-contacts. Notably, when the (p)nc-Si:H layer is thinner than 20 nm, the Ea decreases by applying a hydrogen plasma treatment and a very-high-frequency (i)nc-Si:H treatment. Such an interface treatment also significantly reduces the contact resistivity of the (p)-contact stacks (ρc,p), resulting in an improvement of 6.1%abs in fill factor (FF) of the completed cells. Thinning down the (i)a-Si:H passivating layer to 5 nm leads to a low ρc,p (144 mΩ⋅cm2) for (p)-contact stacks. Interestingly, we observe an increment of FF from 72.9% to 78.3% by using (p)nc-SiOx:H layers featuring larger differences between their optical gap (E04) and Ea, which tend to enhance the built-in potential at the c-Si/(i)a-Si:H interface. Furthermore, we observe clear impacts on ρc,p, open-circuit voltage, and FF by optimizing the thicknesses of (p)-contact that influence its Ea. In front junction cells, the vertical and lateral collection of holes is affected by ρc,p of (p)-contact stacks. This observation is also supported by TCAD simulations which reveal different components of lateral contributions. Lastly, we obtain both front and rear junction cells with certified FF well-above 80% and the best efficiency of 22.47%.