Abstract
Transparent conducting electrode (TCE) thin film materials are featured prominently in many technological applications today, including in thin film solar cells, LEDs, and touchscreens in laptops, smartphones, watches and more. Many of these current technologies use either indium tin oxide (ITO) or fluorinated tin oxide (FTO) as their primary TCE material for their superb optoelectronic properties. Unfortunately, due to the rare earth nature of indium and the growing scarcity of tin, these materials are getting expensive. With growing demand for consumer electronics with TCE technologies, the global demand may soon outstrip their supply.114 Therefore, it is imperative to develop new TCE materials that can be synthesized with earth abundant materials that preserves or enhances the current level of thin film optoelectronic properties. Herein we motivate the copper sulfide (CuS) mineral covellite as an excellent alternative to current industry standard TCE materials and present a novel means of physical vapor deposition (PVD)-based ex situ synthesis. Which produces high quality, consistent and thermodynamically stable copper sulfide thin films with the covellite crystal structure. As transparent conductors, these optimized copper sulfide thin films with thicknesses of 144 nanometers demonstrate average values of 39.4 +/- 2.7% for peak transmission in the visible, 5.99 +/- 0.78 ohms/square sheet resistance, and 1.72 +/- 0.03 eV band gaps. These values compete, directly, with current TCE technologies and indicate that copper sulfide may be a potential earth abundant substitute.