The Structural and Electrochemical Properties of CuCoO2 Crystalline Nanopowders and Thin Films: Conductivity Experimental Analysis and Insights from Density Functional Theory Calculations

Nanomaterials (Basel). 2023 Aug 11;13(16):2312. doi: 10.3390/nano13162312.

Abstract

A novel manufacturing process is presented for producing nanopowders and thin films of CuCoO2 (CCO) material. This process utilizes three cost-effective synthesis methods: hydrothermal, sol-gel, and solid-state reactions. The resulting delafossite CuCoO2 samples were deposited onto transparent substrates through spray pyrolysis, forming innovative thin films with a nanocrystal powder structure. Prior to the transformation into thin films, CuCoO2 powder was first produced using a low-cost approach. The precursors for both powders and thin films were deposited onto glass surfaces using a spray pyrolysis process, and their characteristics were examined through X-ray diffraction, scanning electron microscopy, HR-TEM, UV-visible spectrophotometry, and electrochemical impedance spectroscopy (EIS) analyses were conducted to determine the conductivity in the transversal direction of this groundbreaking material for solar cell applications. On the other hand, the sheet resistance of the samples was investigated using the four-probe method to obtain the sheet resistivity and then calculate the in-plane conductivity of the samples. We also investigated the aging characteristics of different precursors with varying durations. The functional properties of CuCoO2 samples were explored by studying chelating agent and precursor solution aging periods using Density Functional Theory calculations (DFT). A complementary Density Functional Theory study was also performed in order to evaluate the electronic structure of this compound. Resuming, this study thoroughly discusses the synthesis of delafossite powders and their conversion into thin films, which hold potential as hole transport layers in transparent optoelectronic devices.

Keywords: EIS; conductivity; delafossite; films; powder; relaxation time; spray pyrolysis.

Grants and funding

The author Amal Bouich acknowledges MCIN for funding support through Margarita Salas Fellowship (MCIN/AEI/10.13039/501100011033). This work has been funded by the Ministerio de Ciencia e Innovación (Spain) and by the Spanish Agencia Estatal de Investigación through projects BESTMAT PID2019-107137RB-C21/AEI/10.13039/5011000 11033 and PID2019-107137RB-C22/AEI/10.13039/ 501100011033 and by ERDF under the funding “A way of making Europe”.