Origin of passivation in hole-selective transition metal oxides for crystalline silicon heterojunction solar cells
نویسندگان
چکیده
Transition metal oxides (TMOs) have recently attracted interest as an alternative to boron/phosphorous doped layers in crystalline silicon heterojunction solar cells. In this work, the interface between n-type c-Si (n-Si) and three thermally evaporated TMOs (MoO3, WO3 and V2O5) was investigated by transmission electron microscopy and secondary ion-mass/x-ray photoelectron spectroscopy. For the oxides studied, chemical passivation of n-Si was attributed to an ultra-thin (1.9 – 2.8 nm) SiOx~1.5 interlayer formed by chemical reaction, leaving oxygen-deficient species (MoO, WO2 and VO2) as byproducts. Field-effect passivation was also inferred from the inversion (hole-rich) layer induced on the n-Si surface, a result of Fermi level alignment between two materials with dissimilar electrochemical potentials (work function delta Δφ ≥1 eV). Therefore, the holeselective and passivating functionality of these TMOs, in addition to their ambient temperature processing, could prove an effective means to lower cost and simplify solar cell processing. This article has been published in a revised form in Journal of materials research, http://dx.doi.org/ 10.1557/jmr.2016.453. This version is free to view and download for private research and study only. Not for re-distribution, re-sale or use in derivative works. © copyright holder.
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