Topological insulator nanostructures for near-infrared transparent flexible electrodes

Topological insulators are an intriguing class of materials with an insulating bulk state and gapless Dirac-type edge/surface states. Recent theoretical work predicts that few-layer topological insulators are promising candidates for broadband and high-performance optoelectronic devices due to their spin-momentum-locked massless Dirac edge/surface states, which are topologically protected against all time-reversal-invariant perturbations. Here, we present the first experimental demonstration of near-infrared transparent flexible electrodes based on few-layer topological-insulator Bi2Se3 nanostructures epitaxially grown on mica substrates by means of van der Waals epitaxy. The large, continuous, Bi2Se3-nanosheet transparent electrodes have single Dirac cone surface states, and exhibit sheet resistances as low as similar to 330 Omega per square, with a transparency of more than 70% over a wide range of wavelengths. Furthermore, Bi2Se3-nanosheet transparent electrodes show high chemical and thermal stabilities as well as excellent mechanical durability, which may lead to novel optoelectronic devices with unique properties.