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Tantalum Films Improve Solar Cell Power Conversion Efficiency

"Tantalum Films Improve Solar Cell Power Conversion Efficiency"


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Figure1 Electronic characterization of ALD tantalum films

 

(a) and (b) show the core energy level spectra of Ta 4f and O 1s, respectively. (c) shows the valence band spectrum and (d) shows the secondary electron cutoff spectrum with gold (Au) as the reference.

As mentioned above, the tantalum film incorporates a high valence band shift, thereby creating a potential barrier hole transport; however, it is fully passivated unless there is a hole flow at the interface between the tantalum film and Si. Therefore, the carrier selectivity of the n-Si/tantalum film heterostructure needs to be characterized not only by characterizing the contact resistivity ρ, but also by characterizing the surface to evaluate the recombination speed.

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Figure 2

Heterogeneous contacts are schematically shown in (a). (b) A cross-sectional transmission electron micrograph of the back hetero contact is given, showing that the ~6 nm tantalum film consists of a ~1.2 nm interfacial layer and a ~4.5 nm tantalum film. The interfacial layer may be due to the rinse with deionized water during the first few ALDs or exposure to ambient cycles after the water precursor. Photoluminescence image of a complete solar cell using 1025. (c) Nano short-pass filter showing uniform optical, passivation and contact behavior on the cell surface. (d) shows the relationship between solar cell power conversion efficiency and tantalum film. (e) Light J–V curves and electrical parameters of cells with and without ~6 nm tantalum film interlayer. (f) Spectral response (external quantum efficiency and reflectivity).

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Figure3. PEC device results for electronic heterocontact with tantalum film passivation

(a) Illustrates an electronically heterocontacted n-type silicon photocathode passivated using a tantalum film.

(b) Presents the photoelectrochemical current-voltage curves of Si photocathode with and without ~6 nm tantalum film interlayer.

(c) Shows the applied bias photon current efficiency (ABPE).

(d) shows the current-time curves of Si photocathode vs reversible hydrogen electrode (RHE) at 0 V.