Properties of high efficiency silicon heterojunction cells

Bätzner, D.L.; Andrault, Y.; Andreetta, L.; Büchel, A.; Frammelsberger, W.; Guérin, C.; Holm, N.; Lachenal, D.; Meixenberger, J.; Papet, P.; Rau, B.; Strahm, B.; Wahli, G.; Wünsch, F.

doi:10.1016/j.egypro.2011.06.117

Cited by 32 publications

(18 citation statements)

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“…The operating temperature of PV modules can be quite high, and the temperature coefficient, i.e., the efficiency loss per unit change in temperature, is an important parameter. With values of about 0:45%=K for diffused-junction solar cells, high-quality SHJ devices outperform their conventional counterparts in the field with values < 0:25%=K [116,172]. The smaller temperature sensitivity is mainly due to the high V oc of SHJ devices [27].…”

Section: Operation In the Fieldmentioning

confidence: 99%

“…Consequently there is a strong drive for SHJ devices to move to alternative metallization schemes. Recently, good results were achieved using either additional busbars (total of 5) on 6 6 inch 2 pseudo square wafers [116], or densely spaced metallic wires, replacing the busbars using technology developed by Day4 Energy in Canada [117]. An encapsulated SHJ cell with a certified efficiency of 19.3% was achieved using the latter scheme [117].…”

Section: Metallizationmentioning

confidence: 99%

“…Several companies are working on SHJ cells (e.g., Sanyo [27,35,36,38,39,84,172,180,197], Kaneka [121], and CIC [112] in Japan, and Hyundai Heavy Industries [128], and LG Electronics [134] in Korea) and some equipment providers offer production solutions as well, including Roth and Rau, Switzerland/Germany [66,92,116,117]. Challenges for production include sourcing highquality n-type Cz material, carefully controlling all process steps from cleaning to TCO deposition, and developing a module design that is compatible with TCOs and lowtemperature contacting schemes.…”

Section: Industrialisationmentioning

confidence: 99%

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High-efficiency Silicon Heterojunction Solar Cells: A Review

Wolf¹,

Descoeudres²,

Holman³

et al. 2012

Green

108

113

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Abstract. Silicon heterojunction solar cells consist of thin amorphous silicon layers deposited on crystalline silicon wafers. This design enables energy conversion efficiencies above 20% at the industrial production level. The key feature of this technology is that the metal contacts, which are highly recombination active in traditional, diffused-junction cells, are electronically separated from the absorber by insertion of a wider bandgap layer. This enables the record open-circuit voltages typically associated with heterojunction devices without the need for expensive patterning techniques. This article reviews the salient points of this technology. First, we briefly elucidate device characteristics. This is followed by a discussion of each processing step, device operation, and device stability and industrial upscaling, including the fabrication of solar cells with energyconversion efficiencies over 21%. Finally, future trends are pointed out.

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Section: Operation In the Fieldmentioning

confidence: 99%

Section: Metallizationmentioning

confidence: 99%

Section: Industrialisationmentioning

confidence: 99%

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High-efficiency Silicon Heterojunction Solar Cells: A Review

Wolf¹,

Descoeudres²,

Holman³

et al. 2012

Green

108

113

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“…Recently, a record cell efficiency of 23.7% (on 100Â100 mm 2 ) has been presented 1 and several groups have achieved efficiencies of well above 20%. 2,3 Unlike many other high efficiency concepts, the silicon heterojunction concept is based on a rather simple processing scheme consisting of plasma enhanced chemical vapour deposition (PECVD), sputtering and screen printing steps, and all processing steps are carried out at temperatures below 200 to 250 C. The high efficiencies likely originate from low minority carrier recombination rates at the c-Si wafer surfaces passivated by thin layers of intrinsic amorphous silicon (a-Si:H). Without passivation, silicon surface states related to unsaturated and reconstructed dangling bonds are likely causing a rather high surface recombination rate.…”

Section: Introductionmentioning

confidence: 99%

Analysis of sub-stoichiometric hydrogenated silicon oxide films for surface passivation of crystalline silicon solar cells

Einsele¹,

Beyer²,

Rau³

2012

Journal of Applied Physics

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Thermal stability of passivating layers in amorphous/crystalline silicon (a-Si/c-Si) heterojunction solar cells is crucial for industrial processing and long-term device stability. Hydrogenated amorphous silicon (a-Si:H) yields outstanding surface passivation as atomic hydrogen saturates silicon dangling bonds at the a-Si/c-Si interface. Yet, a-Si surface passivation typically starts to degrade already at annealing temperatures in the range of 200 to 250 °C depending on annealing time, and optical absorption in front layers of a-Si reduces the short circuit current density. We show that oxygen incorporation into a-Si:H films enhances the thermal stability of the passivation and reduces parasitic absorption. We further show that for good passivation of the a-Si/c-Si interface, a compact material structure of the a-Si:O:H films is required where atomic hydrogen is the dominating type of diffusing hydrogen species. For plasma deposited a-Si:O:H films, oxygen incorporation of up to 10 at. % leads to an increase of the optical band gap while the hydrogen concentration is almost constant at approximately 10 at. %. For oxygen concentrations below 3%, the films yield surface recombination velocities as low as 10 cm/s on p-type wafers, and the temperature stability improves by about 50 K compared to pure a-Si:H. For films with relatively low oxygen content, hydrogen effusion spectra and Fourier transform infrared spectroscopy (FTIR) indicate a compact microstructure where only atomic H diffuses. For oxygen concentrations above 3%, the passivation quality reduces and H effusion and FTIR suggest the formation of an open, void-rich material where molecular H2 diffuses. In this case, annealing above 400 °C results in improved interface passivation, presumably due to a densification of the material. Likely, this densification results in an increased density of atomic H, which saturates Si dangling bonds near the c-Si interface.

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“…The world record 23.7% SRJ devices of Sanyo was indeed achieved with a wafer only 98 micron thick [2]. The high Vo c translates into favorable temperature coefficient for the module perfonnance, and values well below -O.3%;oC are reported [3]. …”

Section: Basic Principlesmentioning

confidence: 99%