Water-assisted grown ZnO transparent conductive oxide enables efficient thin-film solar cells

Pasini, Stefano and Baraldi, Andrea and Cora, Ildikó and Foti, Gianluca and Kashif, Muhammad and Mezzadri, Francesco and Onuorah, Ifeanyi John and Parisini, Antonella and Pécz, Béla and Shapouri, Samaneh and Sozzi, Giovanna and Spoltore, Donato and Bosio, Alessio (2026) Water-assisted grown ZnO transparent conductive oxide enables efficient thin-film solar cells. JOURNAL OF ALLOYS AND COMPOUNDS, 1057. No. 186907. ISSN 0925-8388

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Abstract

We report the development of a novel water-assisted growth ZnO (HZO) transparent conductive oxide (TCO) deposited by reactive d.c. magnetron sputtering in Ar/O2/H2O atmosphere. Controlled water dosing acts as a surface surfactant, promoting c-axis oriented columnar grains with enhanced crystallinity and superior carrier transport properties. The HZO films exhibit high optical transparency across the visible spectrum (Eg = 3.28 eV) and low resistivity arising from degenerate conduction mechanisms. Electron mobility exceeds 30 cm2 V− 1 s − 1 and the carrier concentration is on the order of 1019 cm− 3 , consistent with a Burstein-Moss blue-shift partially compensated by band-gap renormalization. Density Functional Theory (DFT) supports these findings, elucidating the electronic origin of the Fermi level shift and the interplay between band filling and defect. When integrated as a front contact in Sb2Se3-based solar cell, HZO matches or surpasses conventional ITO or aluminum doped ZnO contacts, improving short circuit current (Jsc) and reducing series resistance due to enhanced light scattering and charge transport. In short, rather than inserting an additional buffer layer, a single HZO layer can directly serve as the TCO, thereby eliminating the free-carrier absorption often seen in ITO as well as the In/Al contamination issues commonly associated with ITO- and AZO-based stacks.

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