Publication: Transport mechanisms in silicon heterojunction solar cells with molybdenum oxide as a hole transport layer
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2018-10
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Elsevier Science BV
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Abstract
Heterojunction solar cells based on molybdenum sub-oxide (MoOx) deposited on n-type crystalline silicon have been fabricated. The hole selective character of MoOx is explained by its high workfunction, which causes a strong band bending in the Si substrate. This bending pushes the surface into inversion. In addition, the sub-stoichiometry of the evaporated MoOx layers leads to a high density of states within the bandgap. This is crucial for charge transport. The J-V electrical characteristics at several temperatures were analysed to elucidate the dominant charge transport mechanisms of this heterojunction structure. We have identified two different transport mechanisms. At low bias voltage, transport is dominated by hole tunnelling through the MoOx gap states. At higher voltage the behaviour is similar to a Schottky junction with a high barrier value, due to the high MoOx work function. These results provide a better understanding of the hole selective character of MoOx/n-type silicon heterocontacts, which is key to further improve this new kind of solar cells.
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© 2018 Elsevier B.V. All rights reserved. Authors would like to acknowledge the CAI de Técnicas Físicas of the Universidad Complutense de Madrid for the use of its laboratories. This work was partially supported by the Project MADRID-PV (Grant No. 2013/MAE-2780) funded by the Comunidad de Madrid, by the Spanish MINECO (Ministerio de Economía y Competitividad) under grants TEC 2013-41730-R, TEC2017-84378-R and ENE2016-78933-C4-1-R. Also by the Universidad Complutense de Madrid (Programa de Financiación de Grupos de Investigación UCM–Banco Santander) under grant 910173-2014. D. Montero acknowledges the Spanish MINECO (Ministerio de Economía y Competitividad) for financial support under contract BES-2014-067585and L.G. Gerling the support from Mexico's grant program CONACyT.