Nature of Record Efficiency Fluid-Processed Nanotube-Silicon Heterojunctions

Although there, has been significant recent progress in improving performance, the precise classification of nanotube-silicon heterojunctions remains ambiguous. Here, we use type, chirality, and length-purified single-walled carbon nanotubes to clarify the nature of these devices. Our junctions are assembled from freestanding nanotube sheets that show remarkable stability in response to repeated crumpling and folding during fluid processing, making the films well suited to flexible platforms. Despite modest ideality factors, the best diodes meet or exceed state-of-the-art characteristics, but with a surprising dependence on sample type. The data further suggest that these devices can be simultaneously categorized as either Schottky or p-n junctions, and we use scaling arguments to model the behavior over a broad range of sheet resistance and film thickness in a manner that highlights the critical role of nanotube midgap states. Our results demonstrate how band gap engineering,can optimize these devices while emphasizing the important role of the junction morphology.