Emitter Saturation Current Density Research Articles

Chemical etching of boron-rich layer and its impact on high efficiency n-type silicon solar cells

This paper reports on an effective chemical etching treatment to remove a boron-rich layer which has a significant negative impact on n-type silicon (Si) solar cells with boron emitter. A nitric acid-grown oxide/silicon nitride stack passivation on the boron-rich layer-etched boron emitter markedly decreases the emitter saturation current density J0e from 430 to 100 fA/cm2. This led to 1.6% increase in absolute cell efficiency including 22 mV increase in open-circuit voltage Voc and 1.9 mA/cm2 increase in short-circuit current density Jsc. This resulted in screen-printed large area (239 cm2) n-type Si solar cells with efficiency of 19.0%.

Higher emitter quality by reducing inactive phosphorus

In this work, we study the influence of the amount of active phosphorus atoms in the emitter region of silicon N+/P solar cells. After emitter formation by thermal diffusion, a part of phosphorus atoms in the vicinity of the surface is electrically inactive. This results in a high emitter saturation current density and in a poor quantum efficiency in the blue wavelength range. This emitter region is usually known as dead layer. We first introduce a simple method to determine the percentage of electrically active phosphorus atoms in emitters obtained from a low pressure POCl3 diffusion furnace. Different phosphorus diffusions are performed using different parameters (temperature, time, POCl3/O2 ratio, and preoxidation time). We then investigate the effect of the fraction of active phosphorus on the doping level and on the emitter passivation. We show that diffusion parameters can greatly influence the active phosphorus percentage, particularly the POCl3/O2 ratio or the addition of a preoxidation step. Concerning the emitter passivation, a linear variation of the emitter saturation current density as a function of the active phosphorus percentage is observed. Using appropriate POCl3/O2 ratio or preoxidation time, we obtain an emitter saturation current density around 100fA/cm2.

On the determination of the emitter saturation current density from lifetime measurements of silicon devices

ABSTRACTContactless photoconductance measurements are commonly used to extract the emitter saturation current density (Joe) for crystalline silicon samples containing an emitter on the surface. We review the physics behind the analysis of Joe and compare the commonly used approximations with more generalised solutions using two‐dimensional device simulations. We quantify errors present in such approximations for different test conditions involving varying illumination conditions and surface properties in samples with the same emitter on both sides. The simulated Joe obtained from the dark hole current from the emitter into the bulk is nearly the same as the simulated Joe determined by photoconductance measurements of the rear diffusion. The simulated Joe at the front emitter is equivalent to that at the rear emitter only when the sample is subject to a nearly constant and flat generation profile. For illumination conditions including visible light, the simulated Joe at the front emitter is smaller than the simulated Joe at the rear emitter. Both Joe at the rear emitter and from the dark hole current in the emitter remain nearly constant over a wide range of base doping densities. The approximations used for the determination of Joe from photoconductance measurements make Joe dependent on the excess minority carrier density. Lifetime measurements demonstrate that, even in high‐quality silicon, Joe should be determined from the analytical solution as a function of excess minority carrier density including Shockley‐Read‐Hall recombination. Copyright © 2012 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

ABSTRACTExcellent passivation of boron emitters is realised using AlOx/SiNx dielectric stacks deposited in an industrial inline plasma‐enhanced chemical vapour deposition reactor. Very low emitter saturation current density (J0e) values of 10 and 45 fA/cm2 are obtained for 180 and 30 Ω/sq planar p+ emitters, respectively. For textured p+ emitters, the J0e was found to be 1.5–2 times higher compared with planar emitters. The required thermal activation of the AlOx films is performed in a standard industrial fast‐firing furnace, making the developed passivation stack industrially viable. We also show that an AlOx thickness of 5 nm in the AlOx/SiNx stack is sufficient for obtaining a J0e 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.

Evaluating The Quality of Selective Emitter Structures by Imaging the Emitter Saturation Current Density

A method to derive the emitter saturation current density J0e with lateral resolution is applied to investigate selective emitter structures. The method uses PL lifetime imaging at several injection densities to laterally evaluate J0e by applying the method of Kane and Swanson [1] pixel by pixel. Samples with two-sided diffused emitters on lowly-doped Cz wafers were used to produce selective emitter structures by laser doping of the phosphorus-rich glass (LD-SE). By comparison of experimental and numerical simulation results of J0e linescans, a limited resolution of a feature size of an inhomogeneous emitter is determined to be theoretically between 0.5-1.0mm and experimentally about 2mm. The method was successfully applied to investigate the dependence of J0e on the laser power of a selective emitter structure. The expected behaviour of a maximum J0e for medium laser intensities is observed. The method is suitable to evaluate the selective emitter process and its optimization.

Comparison of emitter saturation current densities determined by injection‐dependent lifetime spectroscopy in high and low injection regimes

ABSTRACTThe determination of the emitter saturation current density J0e of symmetrical test structures, analyzed by injection‐dependent lifetime spectroscopy (IDLS), in high as well as in low injection regimes is compared. A detailed investigation of the influence of different models for the Auger recombination on the evaluation of the measured minority carrier lifetime is performed. It can be concluded that a good agreement for the extraction of J0e under high and low injection conditions for lightly and highly doped emitters on textured and untextured surfaces was obtained if the Auger parameterization of Kerr et al. is applied. For deep‐diffused emitter profiles on textured surfaces a significant increase of J0e well above the geometrical surface area ratio of untextured and textured surfaces of 1.7 was observed. A verification of the experimentally determined values for J0e is performed by numerical device simulations. The simulated surface recombination velocity for the investigated emitter doping profiles is in good agreement to analytical calculations. Copyright © 2010 John Wiley & Sons, Ltd.

Light‐enhanced surface passivation of TiO2‐coated silicon

ABSTRACTTitanium dioxide is shown to afford good passivation to non‐diffused silicon surfaces and boron‐diffused surfaces after a low‐temperature anneal. The passivation most likely owes to the significant levels of negative charge instilled in the films, and passivation is enhanced by illumination—advantageous for solar cells—indicating that a titanium dioxide photoreaction is at least partly responsible for the low surface recombination. We demonstrate a surface recombination velocity of less than 30 cm/s, on a 5‐Ω cm n‐type silicon, and an emitter saturation current density of 90 fA/cm2 on a 200‐Ω/sq boron diffusion. If these titanium dioxide passivated boron‐diffused surfaces were employed in a crystalline silicon solar cell, an open‐circuit voltage as high as 685 mV could be achieved. Given that TiO2 has a high refractive index and was deposited with atmospheric pressure chemical vapour deposition, an inexpensive technique, it has the potential as a passivating antireflection coating for industrial boron‐diffused silicon solar cells. Copyright © 2011 John Wiley & Sons, Ltd.

Excellent silicon surface passivation with 5 Å thin ALD Al2O3 layers: Influence of different thermal post‐deposition treatments

AbstractThin layers of Al2O3 always require a thermal post‐deposition treatment to activate the passivation on crystalline silicon surfaces. In this work, we studied the influence of different thermal post‐deposition treatments for the activation of passivating ALD Al2O3 single layers and Al2O3/SiNx stacks. For the stacks, especially with less than 5 nm Al2O3, a short high temperature process at ∼800 °C results in a remarkably lower surface recombination compared to a commonly applied annealing at 425 °C. We observed that four ALD cycles of Al2O3 are sufficient to reach the full potential of surface passivation, and even with one atomic layer of Al2O3 (one ALD cycle) emitter saturation current densities as low as 45 fA/cm2 can be reached on boron‐diffused emitters. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Formation of highly aluminum-doped p-type silicon regions by in-line high-rate evaporation

Highly aluminum-doped p-type silicon regions are formed by in-line high-rate evaporation of aluminum. We deposit aluminum layers of 28 μm thickness at dynamic deposition rates of 20 μm×m/min on p-type silicon substrates. Due to the high substrate temperature of up to 770 °C during deposition an Al-doped p + region is formed. Using the camera-based dynamic infrared lifetime mapping technique we measure emitter saturation current densities of 695±65 fA/cm 2 for the fully metalized Al- p + regions, which corresponds to an implied solar cell open-circuit voltage of 635±2 mV.

Evaluating the Aluminum-Alloyed $\hbox{p}^{+}$-Layer of Silicon Solar Cells by Emitter Saturation Current Density and Optical Microspectroscopy Measurements

Surface-passivated and surface-unpassivated aluminum-alloyed p <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> -layers are characterized. By varying the firing conditions and the thickness of the screen-printed aluminum paste, different sheet resistances <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sh</sub> of the p <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> -layer were fabricated. The emitter saturation current density J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0e</sub> plotted versus <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sh</sub> follows distinctly different trends for the passivated and unpassivated samples. An aluminum paste with a boron additive achieves a much higher doping concentration and a lower sheet resistance but nevertheless follows the same J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0e</sub> curves as the pure Al paste. The aluminum p <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> -layer was quantitatively analyzed with microphotoluminescence and Fano-Raman measurements. The latter shows an increased defect recombination at the interface between the p <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> -layer and the moderately doped Si bulk. The lower Shockley-Read-Hall lifetime in this region can be attributed to a high defect concentration in the most highly doped layer, represents an impediment to the reduction of J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0e</sub> for Al-doped emitter regions, and needs to be optimized in future investigations.

Characterization of height-selective emitters

Abstract In this work we characterize height-selective emitters. The concept of a height-selective emitter is similar to the classical selective emitter but applied on a much smaller scale. Concretely, we masked textured wafers by a spin coating oxide. Scanning electron microscopy (SEM) analysis revealed that only the valleys between the tips of the pyramids are covered by the oxide while the tips are open. Thus, subsequent phosphorus diffusion leads to a highly doped emitter on the tips of the pyramids, and a lowly doped emitter at the sides and valleys in between. This was demonstrated by SEM measurements on cross section prepared samples. Further characterization consisted of IV, spectral response, and contact resistivity measurements as well as the determination of the silver crystallites’ distribution, both on height-selective and standard emitter cells with different emitter sheet resistances. In contrast to homogeneous emitter cells, height-selective emitter cells, although exhibiting a high macroscopical sheet resistance, could still be well contacted by standard silver pastes. Just a few silver crystallites at the tips of the pyramids allowed a good contact. Up to 110 Ω/sq fill factors higher than 77.5% could be achieved. The last part of the characterization consisted of carrier lifetime measurements on standard and height-selective emitter samples with symmetric structures to determine the implied open circuit voltage, emitter saturation current density and effective lifetime to identify limiting factors such as emitter, front, and back surface recombination. These measurements demonstrated that height-selective emitters benefit from a lower recombination in the emitter allowing a higher open circuit voltage.

Surface passivation of phosphorus-diffused emitters by inline thermal oxidation

Abstract We show that inline thermal oxidation is a very promising alternative to the use of conventional batch type quartz tube furnaces for the passivation of industrial phosphorus-diffused emitters. Our results reveal that both inline and batch oxidation allow similar results for oxide layer thickness, sheet resistance and, most important, emitter dark saturation current density J 0e even when compressed dry air is used as a cost effective oxygen source. Using a ~10 nm thin thermal oxide layer and a SiN x antireflection coating of adapted thickness, we achieve J 0e values as low as ~100 fA/cm² (68 Ω/sq., textured surface). Using a simple inline oxidation process in air ambient, solar cells with a conventional Al-BSF rear side and a thermal SiO 2 /SiN x passivated front yield average efficiencies of 18.1%, demonstrating 0.3% absolute efficiency gain compared to solely SiN x passivated emitter references. © 2010 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of SiliconPV.

Nanoimprint Lithography for Honeycomb Texturing of Multicrystalline Silicon

Abstract We investigated a novel process chain based on Nanoimprint Lithography (NIL) for realising defined textures. As application we chose the honeycomb texturing of multicrystalline silicon (mc-Si), which so far was applied using elaborate photolithographic processing for reaching the highest efficiencies on this type of substrate material up to now. The developed process chain contains the single steps of interference lithography (master origination of the hexagonal pattern) and cast moulding of silicone (stamp fabrication) as preliminary steps and the repetitive steps of NIL (structuring of the etching mask) and plasma etching (pattern transfer into the mc-Si substrate). First characterization steps of these textured substrates included reflection measurements to evaluate their optical properties as well as determination of emitter saturation current densities to gain information about potential plasma induced damages. These tests were conducted on high-quality float zone monocrystalline silicon to be not affected by material quality issues. Solar cells fabricated out of these test samples showed short circuit current densities exceeding 40 mA/cm 2 , revealing the potential of this texturing scheme. To further increase the feasibility of this process chain we developed a roller-NIL tool, which allows the patterning of UV-curable resists on non transparent, rough and brittle mc-Si substrates in a continuous process flow. Results of imprint quality using this novel tool are also shown in this work.

Impact of surface topography and laser pulse duration for laser ablation of solar cell front side passivating SiNx layers

Local contact openings in SiNx layers that passivate the front side of solar cells offer an attractive alternative to the current standard “fire-through” screen printing process for front grid fabrication. Additionally, this technology can be used for enabling a selective emitter. In the present paper, we investigate laser ablation of SiNx layers on planar and textured silicon surfaces for various laser wavelengths and pulse durations in the nanosecond (ns) to femtosecond (fs) range. We characterize the dark J-V characteristics of diodes with laser contact openings in the SiNx layer passivating the emitter. Our results show that on alkaline textured surfaces the ablation by a ns laser produces less damage than by an ultrashort pulse laser. The dark currents of alkaline textured diodes treated with picosecond (ps) or fs lasers are one order of magnitude higher than those of ns laser treated diodes. High ideality factors furthermore indicate crystal damage in the ∼500 nm deep space charge region of the diodes. Scanning electron microscope and transmission electron microscope images of textured samples, confirm the presence of extensive and deep crystal damage after ps laser ablation, which are not observed in laser treated samples with planar surfaces. Correspondingly, for planar surfaces we find for both, ns and for ps laser ablated regions, emitter saturation current densities J0e,abl of ∼2 pA/cm2. The recombination in textured samples in contrast differs vastly for ns and ps laser ablation. The ns laser results in an only slightly increased value of 3.7 pA/cm2 while the ps laser treated sample was not evaluable due to severe crystal damage leading to effective lifetimes of &amp;lt;5 μs.

The ${\bf ALU}^{+}$ Concept: $N$-Type Silicon Solar Cells With Surface-Passivated Screen-Printed Aluminum-Alloyed Rear Emitter

Aluminum-doped p-type (Al-p <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> ) silicon emitters fabricated by means of screen-printing and firing are effectively passivated by plasma-enhanced chemical-vapor deposited (PECVD) amorphous silicon (a-Si) and atomic-layer-deposited (ALD) aluminum oxide (Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> ) as well as Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> /SiN <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> stacks, where the silicon nitride (SiN <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> ) layer is deposited by PECVD. While the a-Si passivation of the Al-p <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> emitter results in an emitter saturation current density J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> e of 246 fA/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , the Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> /SiN <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</i> double layers result in emitter saturation current densities as low as 160 fA/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , which is the lowest J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> e reported so far for screen-printed Al-doped p <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> emitters. Moreover, the Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> as well as the Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> /SiN <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</i> stacks show an excellent stability during firing in a conveyor belt furnace at 900 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> C. We implement our newly developed passivated Al-p <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> emitter into an n <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> np <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> solar cell structure, the so-called ALU <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> cell. An independently confirmed conversion efficiency of 20% is achieved on an aperture cell area of 4 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , clearly demonstrating the high-efficiency potential of our ALU <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> cell concept.

High-quality nanocrystalline cubic silicon carbide emitter for crystalline silicon heterojunction solar cells

We developed a highly transparent n-type hydrogenated nanocrystalline cubic silicon carbide (nc-3C–SiC:H) emitter for crystalline silicon (c-Si) heterojunction solar cells. A low emitter saturation current density (J0e) of 1.4×101 fA/cm2 was obtained under optimal deposition conditions. A c-Si heterojunction solar cell fabricated on a p-type c-Si wafer without texturing showed an active area efficiency of 17.9% [open-circuit voltage (Voc)=0.668 V, short-circuit current density (Jsc)=36.7 mA/cm2, fill factor=0.731]. The high Jsc value is associated with excellent quantum efficiencies at short wavelengths (&amp;lt;500 nm).

PECVD Silicon Nitride Passivation on Boron Emitter: The Analysis of Electrostatic Charge on the Interface Properties

The dependence of surface recombination of boron diffused and undiffused silicon surfaces passivated with a-Si:H on the net charge density is investigated in detail. The films are deposited by plasma-enhanced chemical vapour deposition using a 2.45 GHz microwave remote plasma system. The surface charge density on the samples is varied by depositing charge using a corona discharge chamber. Excess carrier lifetime, capacitance-voltage, and Kelvin probe measurements are combined to determine the surface recombination velocity and emitter saturation current density as a function of net charge density. Our results show that the application of negative charge causes a substantial reduction in the surface recombination of samples with boron diffused emitters, even for high boron surface concentrations of . The significant difference observed in surface recombination between boron diffused and undiffused sample under accumulation implies that the presence of boron diffusion has results in some degradation of the Si-Si interface. Further, (111) oriented surfaces appear more sensitive to the boron surface concentration than (100) oriented surfaces.

Effectively surface‐passivated aluminium‐doped p+ emitters for n‐type silicon solar cells

AbstractWe present a detailed study on surface‐passivated screen‐printed aluminium‐alloyed emitters for back junction n‐type silicon solar cells. We investigated (i) two different commercially available aluminium pastes and (ii) two passivation layers both well suited for highly doped p+ silicon: plasma‐enhanced‐chemical‐vapour‐deposited amorphous silicon (a‐Si) and atomic‐layer‐deposited aluminium oxide (Al2O3). We show that for the formation of a homogeneous, non‐shunted emitter, a careful choice of the alloying conditions is essential. Moreover, for a most effective surface passivation, low emitter thicknesses have to be used. Combining these two aspects, we have achieved extraordinary high implied open‐circuit voltages of 673 mV for a‐Si‐ and 685 mV for Al2O3‐passivated Al‐alloyed emitters, corresponding to emitter saturation current densities of 128 and 55 fA/cm2, respectively.

Thermal stability of the Al2O3 passivation on p‐type silicon surfaces for solar cell applications

AbstractAl2O3 has been shown to provide an outstanding passivation quality on p‐type surfaces after annealing at moderate temperatures (∼425 °C). However, most industrial silicon solar cells are based on printing technologies for metallization, including a high temperature firing step for the contact formation. To investigate the thermal stability of the Al2O3 passivation, symmetrical p and p+ np+ lifetime samples were coated with Al2O3 and exposed to typical firing processes at temperatures between 700 °C and 850 °C. Up to a firing temperature of 825 °C the Al2O3 passivation is shown to be stable on highly boron‐doped surfaces. An emitter saturation current density of ∼60 fA/cm2 could be measured for the p+ np+ samples, allowing a maximum open circuit voltage (Voc) &gt;695 mV. The firing stability of the Al2O3 is an important step for the realization of an industrial n‐type silicon solar cell. (© 2009 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Passivation and Depassivation of Si – SiO2 Interfaces with Atomic Hydrogen

The influence of atomic hydrogen on the surface passivation of the interface is investigated. Inductively coupled photoconductivity decay measurements indicate an increase in carrier recombination at the surfaces following atomic hydrogen exposure, as measured by an increase in the emitter saturation current density. These defects are not thermally stable and are removed by subsequent thermal treatments above in . Atomic hydrogen results in the passivation of a certain fraction of thermally stable interface defects. However, the fraction of defects passivated is always slightly lower than can be achieved by exposure to molecular hydrogen. A variation in a sample temperature during atomic H exposure in the range of does not have a significant impact on the passivation efficiency.