Materials Sciences and Applications, 2021, 12, 315-329 https://www.scirp.org/journal/msa ISSN Online: 2153-1188 ISSN Print: 2153-117X DOI: 10.4236/msa.2021.127021 Jul. 2, 2021 315 Materials Sciences and Applications A Comparison of Optical Properties of CuO and Cu 2 O Thin Films for Solar Cell Applications Radu Bunea, Ashwin Kumar Saikumar, Kalpathy Sundaram University of Central Florida, Orlando, USA Abstract Solar energy is becoming more popular and widespread, and consequently, the materials to manufacture solar cells are becoming more limited and cost- ly. Therefore, in order to keep solar energy affordable and available, we must research alternative materials such as copper oxides. Some benefits of copper oxides include being available in abundance, affordable, low toxicity, low bandgap, and a high absorption coefficient—all of which contribute to it be- ing a valuable interest for the manufacturing of solar cells. In this study, CuO thin films were synthesized utilizing RF sputtering technique with deposition occurring at room temperature followed by thermal annealing between 100˚C and 400˚C and using different gases, oxygen (O 2 ) (oxidizing and reactive gas) and nitrogen (N 2 ) (inert gas), besides air. Afterwards, these thin films were evaluated for a range of wavelengths: 200 - 400 nm (UV spectrum), 400 - 700 nm (Visible spectrum), and 700 - 800 nm (IR spectrum), for both, optical transmittance and photoluminescence. In addition, the CuO results were com- pared to our Cu 2 O results from a previous study to assess their differences. In the results of this study, the CuO thin film initially had a bandgap of 2.19 eV at room temperature, and by increasing the annealing temperature to differ- ent levels, the bandgap decreased respectively. The presence of air in the chamber allowed for the highest decrease, followed by the nitrogen (N 2 ) and the lowest decrease was observed in the presence of oxygen (O 2 ). This was re- flected in the decrease in the bandgap values from 2.19 eV (room tempera- ture) to 2.05 eV for the films annealed at 400˚C. Keywords Cu 2 O Thin Film, Cuo Thin Film, Optical Properties, Bandgap, Photoluminescence 1. Introduction The current materials used to manufacture photovoltaics are becoming scarce, How to cite this paper: Bunea, R., Saiku- mar, A.K. and Sundaram, K. (2021) A Com- parison of Optical Properties of CuO and Cu 2 O Thin Films for Solar Cell Applica- tions. Materials Sciences and Applications, 12, 315-329. https://doi.org/10.4236/msa.2021.127021 Received: May 5, 2021 Accepted: June 29, 2021 Published: July 2, 2021 Copyright © 2021 by author(s) and Scientific Research Publishing Inc. This work is licensed under the Creative Commons Attribution International License (CC BY 4.0). http://creativecommons.org/licenses/by/4.0/ Open Access