• Katerski, Atanas
• Acik, Ilona Oja
• Spalatu, Nicolae
• Mere, Arvo
• Oluwabi, Abayomi T.
• Maticiuc, Natalia
• Krunks, Malle

Abstract

<jats:p>The deposition of nickel oxide (NiO<jats:sub>x</jats:sub>) thin film from an acetylacetonate source using many solution-based techniques has been avoided owing to its poor solubility in alcohol solvents. From this perspective, this work provides a systematic investigation of the development of NiO<jats:sub>x</jats:sub> thin film, using a combinative approach of ultrasonic spray pyrolysis (USP) and Li dopant for the synthesis and optimization of structural and optoelectronic properties of the films. An in-depth comparative analysis of nickel acetylacetonate-based precursor, employing acetonitrile and methanol as solvents, is provided. It is demonstrated that USP from acetylacetonate precursor yielded uniform, well-compact, and transparent films, with polycrystalline cubic NiO<jats:sub>x</jats:sub> crystal structures. By screening the deposition temperature in the range of 300–450°C, a temperature of 400°C was identified as an optimal processing temperature leading to uniform, compact, highly transparent, and p-type conductive films. At optimized deposition conditions (400°C), lithium-doped NiO<jats:sub>x</jats:sub> (Li:NiO<jats:sub>x</jats:sub>) thin film was deposited. The shift of the main (200) XRD peak position from 43.48° (0-Li:NiO<jats:sub>x</jats:sub>) to 43.56° (60-Li:NiO<jats:sub>x</jats:sub>) indicated Li incorporation into the NiO<jats:sub>x</jats:sub> lattice. An X-ray photoelectron spectroscopy (XPS) study was employed to unravel the incorporation of Li into the deposited Li:NiO<jats:sub>x</jats:sub> thin films. With the deconvolution of the Ni 2p core level for the as-deposited (0, 60)-Li:NiO<jats:sub>x</jats:sub> films, the intensity of Ni<jats:sup>3+</jats:sup> related peak was found to increase slightly with Li doping. Furthermore, all the deposited Li:NiO<jats:sub>x</jats:sub> thin films showed p-type conductivity behavior, and the resistivity was reduced from 10<jats:sup>4</jats:sup> Ωcm (0-Li:NiO<jats:sub>x</jats:sub>) to 10<jats:sup>2</jats:sup> Ωcm (60-Li:NiO<jats:sub>x</jats:sub>). Based on these results, the deposited NiO<jats:sub>x</jats:sub> and Li:NiO<jats:sub>x</jats:sub> thin films suggested that USP-deposited Li:NiO<jats:sub>x</jats:sub> is highly suitable for application in inverted structure solar cells as the hole transport layer.</jats:p>

Topics

• Deposition
• impedance spectroscopy
• nickel
• resistivity
• x-ray diffraction
• thin film
• x-ray photoelectron spectroscopy
• ultrasonic
• Lithium
• alcohol
• solution processing
• spray pyrolysis