Analysis of lateral transport through the inversion layer in amorphous silicon/crystalline silicon heterojunction solar cells

Miha Filipič, Zachary C. Holman, Franc Smole, Stefaan De Wolf, Christophe Ballif, Marko Topič

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59 Scopus citations


In amorphous/crystalline silicon heterojunction solar cells, an inversion layer is present at the front interface. By combining numerical simulations and experiments, we examine the contribution of the inversion layer to lateral transport and assess whether this layer can be exploited to replace the front transparent conductive oxide (TCO) in devices. For this, heterojunction solar cells of different areas (2 × 2, 4 × 4, and 6 × 6 mm 2) with and without TCO layers on the front side were prepared. Laser-beam-induced current measurements are compared with simulation results from the ASPIN2 semiconductor simulator. Current collection is constant across millimeter distances for cells with TCO; however, carriers traveling more than a few hundred microns in cells without TCO recombine before they can be collected. Simulations show that increasing the valence band offset increases the concentration of holes under the surface of n-type crystalline silicon, which increases the conductivity of the inversion layer. Unfortunately, this also impedes transport across the barrier to the emitter. We conclude that the lateral conductivity of the inversion layer may not suffice to fully replace the front TCO in heterojunction devices.

Original languageEnglish (US)
Article number074504
JournalJournal of Applied Physics
Issue number7
StatePublished - Aug 21 2013
Externally publishedYes

Bibliographical note

Funding Information:
The authors would like to thank Antoine Descoeudres, Johannes Peter Seif, and Loris Barraud for their help in making samples, and Marko Berginc for help with measurements. Funding for this work was provided by the European Union Seventh Framework Programme (FP7/2007-2013), Collaborative Project (CP) “20plμs,” Axpo Naturstrom Fonds, Switzerland, the Swiss CTI (Project 9908 PFNMM-NM) The Slovenian Research Agency (P2-0197), and The Slovene Human Resources and Scholarship Fund.

ASJC Scopus subject areas

  • General Physics and Astronomy


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