WS${}_2$ Monolayer Integration in a FAPbI${}_3$-based Heterostructure

Abstract

Incorporating a monolayer of WS${}_2$ via interface engineering enhances the overall physical properties of a FAPbI3 perovskite based heterostructure. FAPbI${}_3$/WS${}_2$/TiO${}_2$/ITO and FAPbI${}_3$/TiO${}_2$/ITO heterostructures were analyzed by UV-Vis spectroscopy, X-ray diffraction, scanning electron microscopy and atomic force microscopy. The configuration with WS${}_2$ interlayer presents higher absorption in the visible region with a bandgap of {\aprox} 1.44 eV. WS${}_2$ also enhances the deposition process of FAPbI${}_3$, resulting in the formation of pure photoactive $\alpha$-phase without the non-photoactive $\delta$-phase nor residual plumbates. The incorporation of the monolayer improves the crystalline structure of the FAPbI${}_3$, promoting a preferential growth in the [100] direction. The smooth surface of WS${}_2$ favors a homogeneous morphology and an increase of the grain size to ~4.5 $\mu$m, the largest reported for similar structures. Furthermore, the work function obtained lets us propose an enhance an adequate energy band alignment between FAPbI${}_3$ and the n-type layers for the electron flux to the cathode. These findings strongly suggest that the interfacial coupling of FAPbI${}_3$/WS${}_2$ could be a promising candidate in photovoltaic applications.

arXiv comment13 pages, 4 figures

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