2.1.3. Film Preparation

2 mg mL−<sup>1</sup> CCO and Mg:CCO suspensions were drop cast on gold-coated silicon substrates for EDX (Zeiss Supra 40) and XPS and on Cu grids (Ted Pella, Inc., Redding, CA, USA) for TEM imaging. CCO and Mg:CCO suspensions were spin coated multiple times on glass substrates for UV-vis (Ocean Optics USB 4000, Largo, FL, USA), spectroscopic ellipsometry (J. A. Woollam M-2000DI, Lincoln, NE, USA), and PESA (RKI Instruments Model AC-2, Union City, CA, USA), and on ITO substrates for SEM (Zeiss Supra 40, Lewisville, TX, USA) and KP (KP Technology SKP 5050, Caithness, Scotland) measurements and solar cells. After spin coating, the CCO and Mg:CCO films were annealed on a hot plate (120–175 ◦C) for 5 min in air to evaporate the solvent.
