Optimisation of electronic interface properties of a-Si:H/c-Si hetero-junction solar cells by wet-chemical surface pre-treatment

Angermann, H.; Korte, Lars; Rappich, Jörg; Conrad, E.; Sieber, I.; Schmidt, M.; Hübener, K.; Hauschild, Jan-Peter

doi:10.1016/j.tsf.2007.12.033

Cited by 52 publications

(25 citation statements)

References 20 publications

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“…Fortunately, this morphology can be accurately controlled: by varying anisotropic etching process, different textures can be achieved with different pyramid sizes and thus densities. Moreover, by applying a post isotropic etching, a modification of the surface morphology, rounding the top and the valleys of pyramids, is achieved [6,7). All these parameters appear to be crucial when amorphous silicon passivating layer is deposited on top of the textured wafer.…”

Section: Introductionmentioning

confidence: 99%

Modification of textured silicon wafer surface morphology for fabrication of heterojunction solar cell with open circuit voltage over 700 mV

Fesquet

Olibet

Damon-Lacoste

et al. 2009

2009 34th IEEE Photovoltaic Specialists Conference (PVSC)

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Crystalline silicon wafer (c-Si) can be extremely well passivated by plasma enhanced chemical vapor deposited (PECVD) amorphous silicon (a-Si:H) films. As a result, on flat substrates, solar cells with very high open circuit voltage are readily obtained. On textured substrates however the passivation is more cumbersome, likely due to the presence of localized recombinative paths situated at the pyramid valleys. Here, we show that this issue may be resolved by selecting a silicon substrate morphology featuring large pyramids. Chemical post-texturization treatments can further reduce the surface recombination velocity. This sequence has allowed us to fabricate solar cells with open circuit voltage over 700 mV, demonstrating also on device level the effect of pyramid density and surface micro-roughness on the surface passivation quality.

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Section: Introductionmentioning

confidence: 99%

Modification of textured silicon wafer surface morphology for fabrication of heterojunction solar cell with open circuit voltage over 700 mV

Fesquet

Olibet

Damon-Lacoste

et al. 2009

2009 34th IEEE Photovoltaic Specialists Conference (PVSC)

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“…According to our recently reported results [21], the preparation-induced surface charge, surface state density D and interface recombination loss of charge carriers on textured p-type surfaces can be reduced by a special wet-chemical smoothing and H-termination process. Applying a special sequence of wet-chemical oxidation and oxide etching in HF containing solutions, the damaged surface region was removed and the microroughness of structured surfaces was reduced on the nmmeter scale.…”

Section: Determination Of the Energetic Distribution Of Preparation-imentioning

confidence: 58%

“…Applying a special sequence of wet-chemical oxidation and oxide etching in HF containing solutions, the damaged surface region was removed and the microroughness of structured surfaces was reduced on the nmmeter scale. The application of optimized wet-chemical surface pre-treatment on p-type substrates with pyramidal light trapping structures enhanced the solar cell efficiency of amorphous-crystalline hetero-junction solar cells on ptype Si absorbers (ZnO/a-Si:H(n)/c-Si(p)/Al) from 17.4% (confirmed) [22] up to 18.4% [21]. Also on n-type substrates, textured by Si(111) pyramids, the high density of states in the lower part of the gap, measured after standard H-termination procedure [10] (Fig.…”

Section: Determination Of the Energetic Distribution Of Preparation-imentioning

confidence: 99%

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Wet-chemical treatment and electronic interface properties of silicon solar cell substrates

Rappich

Klimm

2009

Open Physics

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Abstract:On textured n-type silicon substrates for solar cell manufacturing, the relation between light trapping behavior, structural imperfections, energetic distribution of interface state densities and interface recombination losses were investigated by applying surface sensitive techniques. The field-modulated surface photovoltage (SPV), in-situ photoluminescence (PL) measurements, total hemispherical UV-NIR-reflectance measurements and electron microscopy (SEM) were employed to yield detailed information on the influence of wet-chemical treatments on preparation induced micro-roughness and electronic properties of polished and textured silicon substrates. It was shown that isotropic as well as anisotropic etching of light trapping structures result in high surface micro-roughness and density of interface states. Removing damaged surface layers in the nm range by wet-chemical treatments, the density of these states and the related interface recombination loss can be reduced. In-situ PL measurements were applied to optimise HF-treatment times aimed at undamaged, oxide-free and hydrogen-terminated substrate surfaces as starting material for subsequent solar cell preparations. 73.20.At; 73.50.Pz; 81.65.Cf; 81.65 PACS (2008):

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“…These processes have the advantage of decreasing the reflectance, resulting in an improved light trapping and a subsequent higher photoconverted current in the solar cells. The aSi:H/c-Si interface can be affected by the introduction of these texturization steps in the process as the roughness of the formed structures increases the surface recombination velocity [4] decreasing the minority carrier lifetime. Therefore, a compromise between both, collection of light and an adequate surface passivation should be achieved.…”

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confidence: 99%

A comparative study on different textured surfaces passivated with amorphous silicon

Montesdeoca-Santana

Ziegler

Lindekugel

et al. 2010

Phys. Status Solidi (c)

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In this work it is studied the influence of different texturizations on minority carrier lifetime of n-type Fz silicon wafers passivated with thin amorphous silicon layers (a-Si:H). For amorphous-crystalline silicon based heterojunction solar cells a good light trapping is essential. Therefore a front side texturization is needed as it can increase the photocurrent due to its low reflectance. The interface between the amorphous emitter and the crystalline base plays an important role for two reasons: firstly, the micromorphic surface topology can generate different deposition regimes that results in different lifetimes, and secondly, the nanomorphic structure also show influences on the lifetime. We compare two different types of wet chemical texturizations by different carbonate solutions and a plasma texturization subsequently covered by a thin layer of a-Si:H by means of plasma-enhanced chemical vapor deposition. The surface morphology produced by the texturization on the silicon wafers is analyzed by scanning electron microscopy and atomic force microscopy. The quality of the passivation of the textured silicon surface by the a-Si:H deposition is evaluated by measuring minority carrier lifetimes with a microwave photo-conductance decay and quasi steady state photo-conductance devices

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Optimisation of electronic interface properties of a-Si:H/c-Si hetero-junction solar cells by wet-chemical surface pre-treatment

Cited by 52 publications

References 20 publications

Modification of textured silicon wafer surface morphology for fabrication of heterojunction solar cell with open circuit voltage over 700 mV

Modification of textured silicon wafer surface morphology for fabrication of heterojunction solar cell with open circuit voltage over 700 mV

Wet-chemical treatment and electronic interface properties of silicon solar cell substrates

A comparative study on different textured surfaces passivated with amorphous silicon

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