Brüssel, Belgien  /  24.9.2018  -  28.9.2018


European PV Solar Energy Conference and Exhibition

Bereits zum 35. Mal treffen sich die Spezialisten der Photovoltaik-Solar-Branche auf der EU PVSEC, um neue Konzepte, Trends und Entwicklungen in Wissenschaft und Industrie zu diskutieren.

Madeleiene Justianto, Doktorandin in der Gruppe »Heißdraht-CVD« des Fraunhofer IST präsentiert auf der internationalen Konferenz ihre Forschungsergebnisse zur Abscheidung von intrinsischen amorphen Silikonschichten für Heteroübergang Solarzellen mittels Heißdraht-CVD anhand eines Posters.



Montag, 24. September 2018


Postersession »Industrial Processes for c-Si Solar Cells / Thin Film Silicon Cells«

17:00 - 18:30 Uhr

»Deposition of intrinsic amorphous silicon layers for heterojunction solar cells by hot-wire CVD«

Madeleine Justianto, Markus Höfer, Tino Harig, Volker Sittinger

Using hot-wire chemical vapor deposition (HWCVD) we deposited intrinsic amorphous silicon films (a-Si:H) for silicon heterojunction (SHJ) solar cells. SHJ solar cells have proven to produce high-efficiency devices and were reported recently by Kaneka to achieve conversion efficiencies of more than 26 %. The key to success of SHJ devices is the insertion of a thin passivation layer between the crystalline substrate and the ohmic layer in order to separate the highly recombination-active contacts from the crystalline surface by its wide bandgap. By using HWCVD technology, the growth of the silicon layers takes place with high deposition rates in complete absence of ions and highly energetic particles, which promises highly efficient solar cells in addition to low costs of ownership.

The a-Si:H layers were deposited on etched n-type semi-square wafers with resistivities of ~4 Ω cm and sizes of 156 mm x 156 mm. At pre-optimized values for pressure, filament temperature and silane gas flow, film thickness d and substrate temperature Tsub were investigated in order to identify the influences on the passivation properties. Using the photoconductance method (Sinton WCT-100) the differently prepared amorphous films were characterized by the minority-carrier lifetimes, measured at five positions of each sample after a post annealing at 220 °C in air.

Layer thickness was measured by contact stylus profilometry on planar silicon substrates, and then corrected by the factor 1/√3 for estimating the thickness for the used textured surfaces. The correction factor 1/√3 was verified by SEM analysis of cross-sections of coated textured wafers prepared by focused ion beam (FIB). In order to enhance the contrast between the silicon substrate and the deposited a-Si:H layers we used a niobium oxide (Nb2O5) interlayer prepared by atomic layer deposition (ALD).