High performance metal microstructure for carbon-based transparent conducting electrodes

• Published in: Thin solid films Vol. 520; no. 15; pp. 4827 - 4830
• Main Authors: Kasry, Amal, El Ashry, Mostafa, Nistor, Razvan A., Bol, Ageeth A., Tulevski, George S., Martyna, Glenn J., Newns, Dennis M.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 31.05.2012; Elsevier
• Subjects: Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Fullerenes and related materials; diamonds, graphite; Graphene; Materials science; Nanoscale materials and structures: fabrication and characterization; Nanotubes; Other topics in nanoscale materials and structures; Photovoltaics; Physics; Specific materials; Structure and morphology; thickness; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Thin film structure and morphology; Transparent conducting electrodes; Transparent conducting electrodes; Graphene; Nanotubes; Photovoltaics; Carbon nanotubes; Contact resistance; Palladium; Carbon; Photovoltaic cell; Thin films; Multilayers; Sheet resistivity; Absorption spectra; Copper; Microstructure; Transparent material; Nanostructured materials; Optical absorption
• ISSN: 0040-6090; 1879-2731
• DOI: 10.1016/j.tsf.2012.01.031

In this work, a metal busbar microstructure is introduced to decrease the effective sheet resistance of both graphene and carbon nanotube films to a value suitable for use as transparent conducting electrodes (TCEs). The proposed busbar architecture, implemented with Cu, theoretically can reduce the sheet resistance by a factor of 1000, while yet limiting the optical absorption to 4%. Experimental sheet resistance and optical transparency data are presented for two metals with differing contact resistance (Pd and Cu) and for mono- and multi-layer graphene as well as nanotube films. It is found that the metal busbar microstructure decreases the sheet resistance by a factor of 8 and 70 on graphene and nanotube films respectively, a sufficient resistance reduction to enable utilization as a TCE. The contact resistance between the metal grid and carbon film is believed to limit the ultimate performance. The metal busbar microstructure provides a viable route to the use of carbon films in photovoltaic and display applications. ► A hybrid Transparent Conducting Layer (TCL) for Solar Cells is fabricated. ► The TCL consists of metal busbar+fingers overlaying graphene or a nanotube matrix. ► Graphene film sheet resistance was decreased to 20Ω/□ at 90% transmittance. ► Nanotube film sheet resistance was decreased to 5Ω/□ at 70% transmittance. ► This hybrid TCL can be used in photovoltaic and display applications.