Fabrication conditions for solution-processed high-mobility ZnO thin-film transistors

Stable, solution-processed, non-toxic, high-mobility thin-film semiconductors are required for fabricating low-cost thin-film transistor (TFT) arrays and circuits to enable ubiquitous large-area and ultra low-cost electronics. Most thin-film semiconductors reported to date have been unable to meet the mobility, stability, safety, and cost requirements for this emerging technology, thus precluding their adoption in practical applications. Here, we report the preparation of stable, non-toxic, transparent, high performance zinc oxide (ZnO) thin-film semiconductors via thermal processing of solution-deposited precursor thin films in air. The process conditions influence the performance of the TFTs. By optimizing the fabrication conditions, the prepared ZnO thin-film semiconductor has a well-controlled, preferential crystal orientation and densely packed ZnO crystals, exhibiting excellent field-effect performance characteristics with mobility far exceeding those of hydrogenated amorphous silicon (a-Si:H). Consistently reproducible mobility ∼5–6 cm2V−1s−1 and current on-to-off ratio ∼105–106 have been obtained, while the production cost was controlled as low as possible. This potentially opens up application opportunities inaccessible by a-Si:H technology and renders otherwise costly large-area electronics affordable.