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Thermal Stability of Hole-Selective Tungsten Oxide: In Situ Transmission Electron Microscopy Study.

ABSTRACT: In this study, the thermal stability of a contact structure featuring hole-selective tungsten oxide (WOx) and aluminum deposited onto p-type crystalline silicon (c-Si/WOx/Al) was investigated using a combination of transmission line measurements (TLM) and in situ transmission electron microscopy (TEM) studies. The TEM images provide insight into why the charge carrier transport and recombination characteristics change as a function of temperature, particularly as the samples are annealed at temperatures above 500?°C. In the as-deposited state, a???2?nm silicon oxide (SiOx) interlayer forms at the c-Si/WOx interface and a???2-3?nm aluminum oxide (AlOx) interlayer at the WOx/Al interface. When annealing above 500?°C, Al diffusion begins, and above 600?°C complete intermixing of the SiOx, WOx, AlOx and Al layers occurs. This results in a large drop in the contact resistivity, but is the likely reason surface recombination increases at these high temperatures, since a c-Si/Al contact is basically being formed. This work provides some fundamental insight that can help in the development of WOx films as hole-selective rear contacts for p-type solar cells. Furthermore, this study demonstrates that in situ TEM can provide valuable information about thermal stability of transition metal oxides functioning as carrier-selective contacts in silicon solar cells.

SUBMITTER: Ali H

PROVIDER: S-EPMC6107557 | biostudies-literature | 2018 Aug

REPOSITORIES: biostudies-literature

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