Approach for Al2O3 rear surface passivation of industrial p‐type Si PERC above 19%

Atomic layer deposition (ALD) of thin Al₂O₃ (≤10 nm) films is used to improve the rear surface passivation of large‐area screen‐printed p‐type Si passivated emitter and rear cells (PERC). A blister‐free stack of Al₂O₃/SiO_x/SiN_x is developed, leading to an improved back reflection and a rear recombination current (J_0,rear) of 92 ± 6 fA/cm². The Al₂O₃/SiO_x/SiN_x stack is blister‐free if a 700°C anneal in N₂ is performed after the Al₂O₃ deposition and prior to the SiO_x/SiN_x capping. A clear relationship between blistering density and lower open‐circuit voltage (V_OC) due to increased rear contacting area is shown. In case of the blister‐free Al₂O₃/SiO_x/SiN_x rear surface passivation stack, an average cell efficiency of 19.0% is reached and independently confirmed by FhG‐ISE CalLab. Compared with SiO_x/SiN_x‐passivated PERC, there is an obvious gain in V_OC and short‐circuit current (J_SC) of 5 mV and 0.2 mA/cm², respectively, thanks to improved rear surface passivation and rear internal reflection. Copyright © 2012 John Wiley & Sons, Ltd.     

20.7% efficient ion‐implanted large area n‐type front junction silicon solar cells with rear point contacts formed by laser opening and physical vapor deposition

In this work, we report on ion‐implanted, high‐efficiency n‐type silicon solar cells fabricated on large area pseudosquare Czochralski wafers. The sputtering of aluminum (Al) via physical vapor deposition (PVD) in combination with a laser‐patterned dielectric stack was used on the rear side to produce front junction cells with an implanted boron emitter and a phosphorus back surface field. Front and back surface passivation was achieved by thin thermally grown oxide during the implant anneal. Both front and back oxides were capped with SiN_x, followed by screen‐printed metal grid formation on the front side. An ultraviolet laser was used to selectively ablate the SiO₂/SiN_x passivation stack on the back to form the pattern for metal–Si contact. The laser pulse energy had to be optimized to fully open the SiO₂/SiN_x passivation layers, without inducing appreciable damage or defects on the surface of the n⁺ back surface field layer. It was also found that a low temperature annealing for less than 3 min after PVD Al provided an excellent charge collecting contact on the back. In order to obtain high fill factor of ~80%, an in situ plasma etching in an inert ambient prior to PVD was found to be essential for etching the native oxide formed in the rear vias during the front contact firing. Finally, through optimization of the size and pitch of the rear point contacts, an efficiency of 20.7% was achieved for the large area n‐type passivated emitter, rear totally diffused cell. Copyright © 2014 John Wiley & Sons, Ltd.     

Evaluation of advanced p‐PERL and n‐PERT large area silicon solar cells with 20.5% energy conversion efficiencies

In this paper, we evaluate p‐type passivated emitter and rear locally diffused (p‐PERL) and n‐type passivated emitter and rear totally diffused (n‐PERT) large area silicon solar cells featuring nickel/copper/silver (Ni/Cu/Ag) plated front side contacts. By using front emitter p‐PERL and rear emitter n‐PERT, both cell structures can be produced with only a few adaptations in the entire process sequence because both feature the same front side design: homogeneous n⁺ diffused region with low surface concentration, SiO₂/SiN_x:H passivation, Ni/Cu/Ag plated contacts. Energy conversion efficiencies up to 20.5% (externally confirmed at FhG‐ISE Callab) are presented for both cell structures on large area cells together with power‐loss analysis and potential efficiency improvements based on PC1D simulations. We demonstrate that the use of a rear emitter n‐PERT cell design with Ni/Cu/Ag plated front side contacts enables to reach open‐circuit voltage values up to 676 mV on 1–2 Ω cm n‐type CZ Si. We show that rear emitter n‐PERT cells present the potential for energy conversion efficiencies above 21.5% together with a strong tolerance to wafer thickness and bulk resistivity. Copyright © 2014 John Wiley & Sons, Ltd.     

Experimental evidence of parasitic shunting in silicon nitride rear surface passivated solar cells

Many solar cells incorporating SiN_x films as a rear surface passivation scheme have not reached the same high level of cell performance as solar cells incorporating high‐temperature‐grown silicon dioxide films as a rear surface passivation. In this paper, it is shown by direct comparison of solar cells incorporating the two rear surface passivation schemes, that the performance loss is mainly due to a lower short‐circuit current while the open‐circuit voltage is equally high. With a solar cell test structure that features a separation of the rear metal contacts from the passivating SiN_x films, the loss in short‐circuit current can be reduced drastically. Besides a lower short‐ circuit current, dark I–V curves of SiN_x rear surface passivated solar cells exhibit distinct shoulders. The results are explained by parasitic shunting of the induced floating junction (FJ) underneath the SiN_x films with the rear metal contacts. The floating junction is caused by the high density of fixed positive charges in the SiN_x films. Other two‐dimensional effects arising from the injection level dependent SRV of the Si/SiN_x interfaces are discussed as well, but, are found to be of minor importance. Pinholes in the SiN_x films and optical effects due to a different internal rear surface reflectance can be excluded as a major cause for the performance loss of the SiN_x rear surface passivated cells. Copyright © 2002 John Wiley & Sons, Ltd.     

Diffusion‐free high efficiency silicon solar cells

Traditional POCl₃ diffusion is performed in large diffusion furnaces heated to ~850 C and takes an hour long. This may be replaced by an implant and subsequent 90‐s rapid thermal annealing step (in a firing furnace) for the fabrication of p‐type passivated emitter rear contacted silicon solar cells. Implantation has long been deemed a technology too expensive for fabrication of silicon solar cells, but if coupled with innovative process flows as that which is mentioned in this paper, implantation has a fighting chance. An SiOx/SiN_y rear side passivated p‐type wafer is implanted at the front with phosphorus. The implantation creates an inactive amorphous layer and a region of silicon full of interstitials and vacancies. The front side is then passivated using a plasma‐enhanced chemical vapor deposited SiN_xH_y. The wafer is placed in a firing furnace to achieve dopant activation. The hydrogen‐rich silicon nitride releases hydrogen that is diffused into the Si, the defect rich amorphous front side is immediately passivated by the readily available hydrogen; all the while, the amorphous silicon recrystallizes and dopants become electrically active. It is shown in this paper that the combination of this particular process flow leads to an efficient Si solar cell. Cell results on 160‐µm thick, 148.25‐cm² Cz Si wafers with the use of the proposed traditional diffusion‐free process flow are up to 18.8% with a V_oc of 638 mV, J_sc of 38.5 mA/cm², and a fill factor of 76.6%. Copyright © 2012 John Wiley & Sons, Ltd.     

Surface passivation of high‐efficiency silicon solar cells by atomic‐layer‐deposited Al2O3

Atomic‐layer‐deposited aluminium oxide (Al₂O₃) is applied as rear‐surface‐passivating dielectric layer to passivated emitter and rear cell (PERC)‐type crystalline silicon (c‐Si) solar cells. The excellent passivation of low‐resistivity p‐type silicon by the negative‐charge‐dielectric Al₂O₃ is confirmed on the device level by an independently confirmed energy conversion efficiency of 20·6%. The best results are obtained for a stack consisting of a 30 nm Al₂O₃ film covered by a 200 nm plasma‐enhanced‐chemical‐vapour‐deposited silicon oxide (SiO_x) layer, resulting in a rear surface recombination velocity (SRV) of 70 cm/s. Comparable results are obtained for a 130 nm single‐layer of Al₂O₃, resulting in a rear SRV of 90 cm/s. Copyright © 2008 John Wiley & Sons, Ltd.     

Stack system of PECVD amorphous silicon and PECVD silicon oxide for silicon solar cell rear side passivation

A stack of hydrogenated amorphous silicon (a‐Si) and PECVD‐silicon oxide (SiO_x) has been used as surface passivation layer for silicon wafer surfaces. Very good surface passivation could be reached leading to a surface recombination velocity (SRV) below 10 cm/s on 1 Ω cm p‐type Si wafers. By using the passivation layer system at a solar cell's rear side and applying the laser‐fired contacts (LFC) process, pointwise local rear contacts have been formed and an energy conversion efficiency of 21·7% has been obtained on p‐type FZ substrates (0·5 Ω cm). Simulations show that the effective rear SRV is in the range of 180 cm/s for the combination of metallised and passivated areas, 120 ± 30 cm/s were calculated for the passivated areas. Rear reflectivity is comparable to thermally grown silicon dioxide (SiO₂). a‐Si rear passivation appears more stable under different bias light intensities compared to thermally grown SiO₂. Copyright © 2008 John Wiley & Sons, Ltd.     

Thin Al2O3 passivated boron emitter of n‐type bifacial c‐Si solar cells with industrial process

We have presented thin Al₂O₃ (~4 nm) with SiN_x:H capped (~75 nm) films to effectively passivate the boron‐doped p⁺ emitter surfaces of the n‐type bifacial c‐Si solar cells with BBr₃ diffusion emitter and phosphorus ion‐implanted back surface field. The thin Al₂O₃ capped with SiN_x:H structure not only possesses the excellent field effect and chemical passivation, but also establishes a simple cell structure fully compatible with the existing production lines and processes for the low‐cost n‐type bifacial c‐Si solar cell industrialization. We have successfully achieved the large area (238.95 cm²) high efficiency of 20.89% (front) and 18.45% (rear) n‐type bifacial c‐Si solar cells by optimizing the peak sintering temperature and fine finger double printing technology. We have further shown that the conversion efficiency of the n‐type bifacial c‐Si solar cells can be improved to be over 21.3% by taking a reasonable high emitter sheet resistance. Copyright © 2017 John Wiley & Sons, Ltd.     

An effective way to simultaneous realization of excellent optical and electrical performance in large‐scale Si nano/microstructures

Despite the optical advantage of near‐zero reflection, the silicon nanowire arrays (SiNWs)‐based solar cells cannot yet achieve satisfactory high efficiency because of the serious surface recombination arising from the greatly enlarged surface area. The trade‐off between reflection and recombination fundamentally prevents the conventional SiNWs structure from having both minimal optical and electrical losses. Here, we report the simultaneous realization of the best optical anti‐reflection (the solar averaged reflectance of 1.38%) and electrical passivation (the surface recombination velocity of 44.72 cm/s) by effectively combining the Si nano/microstructures (N/M‐Strus) with atomic‐layer‐deposition (ALD)‐Al₂O₃ passivation. The composite structures are prepared on the pyramid‐textured Si wafers with large‐scale 125 × 125 mm² by the two‐step metal‐assisted chemical etching method and the thermal ALD‐Al₂O₃ treatment. Although the excellent optical anti‐reflection is observed because of the complementary contribution of Si N/M‐Strus at short wavelength and ALD‐Al₂O₃ at long wavelength, the low recombination has also been realized because the field effect passivation is enhanced for the longer and thinner SiNWs through the more effective suppression of the minority carrier movement and the reduction of the pure‐pyramid‐textured surface recombination. We have further numerically modeled the Al₂O₃‐passivated Si N/M‐Strus‐based solar cell and obtain the high conversion efficiency of 21.04%. The present work opens a new way to realize high‐efficiency SiNWs‐based solar cells. Copyright © 2014 John Wiley & Sons, Ltd.     

SiOyNx/SiNx stack: a promising surface passivation layer for high‐efficiency and potential‐induced degradation resistant mc‐silicon solar cells

A thin SiO_yN_x film was inserted below a conventional SiN_x antireflection coating used in c‐Si solar cells in order to improve the surface passivation and the solar cell's resistance to potential‐induced degradation (PID). The effect of varying the flow ratio of the N₂O and SiH₄ precursors and the deposition temperature for the SiO_yN_x thin film upon material properties were systematically investigated. An excellent surface passivation was obtained on FZ p‐type polished silicon wafers, with the best results obtained with a SiO_yN_x film deposited at a very low temperature of 130 °C and with an optical refractive index of 1.8. In the SiO_yN_x/SiN_x stack structure, a SiO_yN_x film with ~6 nm thickness is sufficient to provide excellent surface passivation with an effective surface recombination velocity S_eff < 2 cm/s. Furthermore, we applied the optimized SiO_yN_x/SiN_x stack on multicrystalline Si solar cells as a surface passivation and antireflection coating, resulting in a 0.5% absolute average conversion efficiency gain compared with that of reference cells with conventional SiN_x coating. Moreover, the cells with the SiO_yN_x/SiN_x stack layers show a significant increase in their resistance to PID. Nearly zero degradation in shunt resistance was obtained after 24 h in a PID test, while a single SiN_x‐coated silicon solar cell showed almost 50% degradation after 24 h. Copyright © 2016 John Wiley & Sons, Ltd.     

Laser induced defects in laser doped solar cells

Laser doping offers a promising method to define selective emitters for solar cells. Its main advantage is the localised nature of the laser beam, which allows melting of the surface area without heating the bulk. The ability to perform this process over a dielectric film offers further benefits, such as the possibility of creating self‐aligned metallisation patterns simultaneously with the selective emitter formation. However, laser induced defects, contaminations and discontinuities in the selective emitter can reduce solar cell performance. In this work the influence of different dielectric films on defect formation is investigated. It was found that a thin oxide beneath the SiN_x improves the implied open circuit voltage of the solar cells for a wide range of laser output powers. Fewer defects were observed when using this SiO₂/SiN_x stack compared to the standard single SiN_x anti‐reflection coating layer. It was also found that the recrystallised silicon layer grows epitaxially according the substrate orientation. No dislocation or stacking faults were observed in deeper areas using transmission electron microscopy, although some defects were observed near the surface. Electron beam induced current images revealed discontinuities in junctions formed with high laser powers. We conclude that micro‐cracks create these discontinuities, which can potentially induce shunts. Finally, laser doped solar cells with a standard SiN_x and with a double SiO₂/SiN_x stack layer as anti‐reflection coating were compared. An efficiency of 18.4% on a large area commercial grade p‐type CZ substrate was achieved. Copyright © 2010 John Wiley & Sons, Ltd.     

Large area tunnel oxide passivated rear contact n‐type Si solar cells with 21.2% efficiency

This paper reports on the implementation of carrier‐selective tunnel oxide passivated rear contact for high‐efficiency screen‐printed large area n‐type front junction crystalline Si solar cells. It is shown that the tunnel oxide grown in nitric acid at room temperature (25°C) and capped with n⁺ polysilicon layer provides excellent rear contact passivation with implied open‐circuit voltage iV_oc of 714 mV and saturation current density J_0b′ of 10.3 fA/cm² for the back surface field region. The durability of this passivation scheme is also investigated for a back‐end high temperature process. In combination with an ion‐implanted Al₂O₃‐passivated boron emitter and screen‐printed front metal grids, this passivated rear contact enabled 21.2% efficient front junction Si solar cells on 239 cm² commercial grade n‐type Czochralski wafers. Copyright © 2016 John Wiley & Sons, Ltd.     

Front and rear silicon‐nitride‐passivated multicrystalline silicon solar cells with an efficiency of 18.1%

A solar cell process designed to utilise low‐temperature plasma‐enhanced chemical vapour deposited (PECVD) silicon nitride (SiN_x) films as front and rear surface passivation was applied to fabricate multicrystalline silicon (mc‐Si) solar cells. Despite the simple photolithography‐free processing sequence, an independently confirmed efficiency of 18.1% (cell area 2 × 2 cm²) was achieved. This excellent efficiency can be predominantly attributed to the superior quality of the rear surface passivation scheme consisting of an SiN_x film in combination with a local aluminium back‐surface field (LBSF). Thus, it is demonstrated that low‐temperature PECVD SiN_x films are well suited to achieve excellent rear surface passivation on mc‐Si. Copyright © 2002 John Wiley & Sons, Ltd.     

Progress on large area n‐type silicon solar cells with front laser doping and a rear emitter

We report on the progress of imec's n‐type passivated emitter, rear totally diffused rear junction silicon solar cells. Selective laser doping has been introduced in the flow, allowing the implementation of a shallow diffused front surface field and a reduction of the recombination current in the contact area. Simplifications have been implemented towards a more industrial annealing sequence, by replacing expensive forming gas annealing steps with a belt furnace annealing. By applying these improvements, together with an advanced texturing process and emitter passivation by atomic layer deposition of Al₂O₃, 22.5% efficient cells (three busbars) have been realized on commercial 156 · 156 mm² Czochralski‐Si. This result has been independently confirmed by ISE CalLab. Copyright © 2016 John Wiley & Sons, Ltd.     

Multi‐crystalline Si solar cells with very fast deposited (180 nm/min) passivating hot‐wire CVD silicon nitride as antireflection coating

Hot‐wire chemical vapor deposition (HWCVD) is a promising technique for very fast deposition of high quality thin films. We developed processing conditions for device‐ quality silicon nitride (a‐SiN_x:H) anti‐reflection coating (ARC) at high deposition rates of 3 nm/s. The HWCVD SiN_x layers were deposited on multicrystalline silicon (mc‐Si) solar cells provided by IMEC and ECN Solar Energy. Reference cells were provided with optimized parallel plate PECVD SiN_x and microwave PECVD SiN_x respectively. The application of HWCVD SiN_x on IMEC mc‐Si solar cells led to effective passivation, evidenced by a V_oc of 606 mV and consistent IQE curves. For further optimization, series were made with HW SiN_x (with different x) on mc‐Si solar cells from ECN Solar Energy. The best cell efficiencies were obtained for samples with a N/Si ratio of 1·2 and a high mass density of >2·9 g/cm³. The best solar cells reached an efficiency of 15·7%, which is similar to the best reference cell, made from neighboring wafers, with microwave PECVD SiN_x. The IQE measurements and high V_oc values for these cells with HW SiN_x demonstrate good bulk passivation. PC1D simulations confirm the excellent bulk‐ and surface‐passivation for HW SiN_x coatings. Interesting is the significantly higher blue response for the cells with HWCVD SiN_x when compared to the PECVD SiN_x reference cells. This difference in blue response is caused by lower light absorption of the HWCVD layers (compared to microwave CVD; ECN) and better surface passivation (compared to parallel plate PECVD; IMEC). The application of HW SiN_x as a passivating antireflection layer on mc‐Si solar cells leads to efficiencies comparable to those with optimized PECVD SiN_x coatings, although HWCVD is performed at a much higher deposition rate. Copyright © 2007 John Wiley & Sons, Ltd.     

Development of high‐efficiency large‐area screen‐printed solar cells on direct kerfless epitaxially grown monocrystalline Si wafer and structure

This paper demonstrates the potential of epitaxially grown Si wafers with doped layers for high‐efficiency solar cells. Boron‐doped 239 cm² 180–200 µm thick 2 Ω‐cm wafers were grown with and without 15 µm thick p⁺ layer, with a doping in the range of 10¹⁷~10¹⁸ cm⁻³. A layer transfer process involving porous Si layer to lift off epi‐Si wafers from the reusable substrate was used. The pp⁺ wafers were converted into n⁺pp⁺ passivated emitter rear totally diffused (PERT) cells by forming an oxide‐passivated POCl₃‐diffused n⁺ emitter at the front, and oxide/nitride‐passivated epitaxially grown p⁺ BSF at the entire back, with local screen‐printed contacts. To demonstrate and quantify the benefit of the epi‐grown p⁺ layer, standard passivated emitter and rear cells (PERCs) with local BSF and contacts were also fabricated on p‐type epi‐Si wafers as well on commercial‐grade Cz wafers. Sentaurus 2D device model was used to assess the impact of the epi‐grown p⁺ layer, which showed an efficiency gain of ~0.5% for this PERT structure over the traditional PERC. This was validated by the cell results, which showed an efficiency of ~20.1% for the PERC, and ~20.3% for the PERT cell using epi‐Si wafers. Experimental data showed higher FF in PERT cells, largely because of the decrease in lateral resistance on the rear side. Efficiency gain, a result of higher FF, was greater than the recombination loss in the p⁺ layer because of the lightly doped thick p⁺ epi‐grown region used in this study. Copyright © 2016 John Wiley & Sons, Ltd.     

Laser ablation of SiO2 for locally contacted Si solar cells with ultra‐short pulses

We apply ultra‐short pulse laser ablation to create local contact openings in thermally grown passivating SiO₂ layers. This technique can be used for locally contacting oxide passivated Si solar cells. We use an industrially feasible laser with a pulse duration of τ_pulse ∼ 10 ps. The specific contact resistance that we reach with evaporated aluminium on a 100 Ω/sq and P‐diffused emitter is in the range of 0·3–1 mΩ cm². Ultra‐short pulse laser ablation is sufficiently damage free to abandon wet chemical etching after ablation. We measure an emitter saturation current density of J_0e = (6·2 ± 1·6) × 10⁻¹³ A/cm² on the laser‐treated areas after a selective emitter diffusion with R_sheet ∼ 20 Ω/sq into the ablated area; a value that is as low as that of reference samples that have the SiO₂ layer removed by HF‐etching. Thus, laser ablation of dielectrics with pulse durations of about 10 ps is well suited to fabricate high‐efficiency Si solar cells. Copyright © 2007 John Wiley & Sons, Ltd.     

Economic feasibility of bifacial silicon solar cells

Bifacial solar cells and modules are a promising approach to increase the energy output of photovoltaic systems, and therefore decrease levelized cost of electricity (LCOE). This work discusses the bifacial silicon solar cell concepts PERT (passivated emitter, rear totally diffused) and BOSCO (both sides collecting and contacted) in terms of expected module cost and LCOE based on in‐depth numerical device simulation and advanced cost modelling. As references, Al‐BSF (aluminium back‐surface field) and PERC (passivated emitter and rear) cells with local rear‐side contacts are considered. In order to exploit their bifacial potential, PERT structures (representing cells with single‐sided emitter) are shown to require bulk diffusion lengths of more than three times the cell thickness. For the BOSCO concept (representing cells with double‐sided emitter), diffusion lengths of half the cell thickness are sufficient to leverage its bifacial potential. In terms of nominal LCOE, BOSCO cells are shown to be cost‐competitive under monofacial operation compared with an 18% efficient (≙ p_MPP = 18 mW/cm²) multicrystalline silicon (mc‐Si) Al‐BSF cell and a 19% mc‐Si PERC cell for maximum output power densities of p_MPP ≥ 17.3 mW/cm² and p_MPP ≥ 18.1 mW/cm², respectively. These values assume the use of $10/kg silicon feedstock for the BOSCO and $20/kg for the Al‐BSF and PERC cells. For the PERT cell, corresponding values are p_MPP ≥ 21.7 mW/cm² and p_MPP ≥ 22.7 mW/cm², respectively, assuming the current price offset (≈50%, at the time of October 2014) of n‐type Czochralski‐grown silicon (Cz‐Si) compared with mc‐Si wafers. The material price offset of n‐type to p‐type Cz‐Si wafers (≈15%, October 2014) currently accounts for approximately 1 mW/cm², which correlates to a conversion efficiency difference of 1%_abs for monofacial illumination with 1 sun. From p‐type mc‐Si to p‐type Cz‐Si (≈30% wafer price offset, October 2014), this offset is approximately 2.5 mW/cm² for a PERT cell. When utilizing bifacial operation, these required maximum output power densities can be transformed into required minimum rear‐side illumination intensities for arbitrary front‐side efficiencies η_front by means of the performed numerical simulations. For a BOSCO cell with η_front = 18%, minimum rear‐side illumination intensities of ≤ 0.02 suns are required to match a 19% PERC cell in terms of nominal LCOE. For an n‐type Cz‐Si PERT cell with η_front = 21%, corresponding values are ≤ 0.11 suns with 0.05 suns being the n‐type to p‐type material price offset. This work strongly motivates the use of bifacial concepts to generate lowest LCOE. Copyright © 2016 John Wiley & Sons, Ltd.     

Theory and experiments on the back side reflectance of silicon wafer solar cells

New passivation layers for the back side of silicon solar cells have to show high performance in terms of electrical passivation as well as high internal reflectivity. This optical performance is often shown as values for the back side reflectance R_b which describes the rear internal reflection. In this paper, we investigate in detail the meaning of this single‐value parameter, its correct determination and the use in one‐dimensional simulations with PC1D. The free‐carrier‐absorption (FCA) as non‐carrier‐generating absorption channel is analyzed for solar cells with varying thickness. We apply the optical analysis to samples with different thickness, silicon oxide layer thickness, rear side topography as well as passivation layers (SiO₂, SiN_x, SiC and stack systems). Additionally, the optical influence of the laser‐fired contacts (LFC) process is experimentally investigated. Finally, we show that with correct parameters, the one‐dimensional simulation of very thin silicon solar cells can successfully be performed. Copyright © 2007 John Wiley & Sons, Ltd.     

Excellent boron emitter passivation for high‐efficiency Si wafer solar cells using AlOx/SiNx dielectric stacks deposited in an industrial inline plasma reactor

Excellent passivation of boron emitters is realised using AlO_x/SiN_x dielectric stacks deposited in an industrial inline plasma‐enhanced chemical vapour deposition reactor. Very low emitter saturation current density (J_0e) values of 10 and 45 fA/cm² are obtained for 180 and 30 Ω/sq planar p⁺ emitters, respectively. For textured p⁺ emitters, the J_0e was found to be 1.5–2 times higher compared with planar emitters. The required thermal activation of the AlO_x films is performed in a standard industrial fast‐firing furnace, making the developed passivation stack industrially viable. We also show that an AlO_x thickness of 5 nm in the AlO_x/SiN_x stack is sufficient for obtaining a J_0e of 18 fA/cm² for planar 80 Ω/sq p⁺ emitters, which corresponds to a 1‐sun open‐circuit voltage limit of the solar cell of 736 mV at 25 °C. Copyright © 2012 John Wiley & Sons, Ltd.