Ligand-exchange-assisted printing of colloidal nanocrystals to enable all-printed sub-micron optoelectronics
Zhixuan Zhao, Ran An, Yu Liu, Byung Ku Jung, Jun Hyuk Ahn, Yang Ni, Guodan Wei, Wallace C. H. Choy, Lain‐Jong Li, Soong Ju Oh, Ji Tae Kim, Tianshuo Zhao
Abstract
Additive manufacturing enables customised device fabrication for emerging sensing technologies. However, printable (opto)electronic devices with sophisticated architectures, including all-printed photodiodes, face challenges in multi-material and multi-layer printing at micro- and nanoscales with low processing temperatures. Herein, we establish a nano-resolution printing method based on electrohydrodynamic printing (EHDP) to deposit inks from the colloidal nanocrystal (NC) library, followed by in situ room-temperature ligand exchange to functionalise the NC solids. This general approach enables layer-by-layer printing with wide selections of NC inks, ligand reagents, substrates, and device architectures. Chemical-treatment-induced contraction and densification grants printed Ag NC structures electrical conductivity and an achievable feature size and filling ratio of 70 nm and 75%, respectively, constructing wide-gamut structural colour gratings. By exploiting Ag, Au, PbS, and ZnO NCs and compact ligands, we demonstrate all-printed multi-layer infrared photodiodes with sub-10-µm pixel sizes. The nano-printing assembly of hetero-NCs promises the facile integration of multi-functional micro-nano devices. Researchers developed a nano-resolution, multi-material, and multi-layer printing method for the colloidal nanocrystal library. The electrohydrodynamic technique is enabled by in-situ ligand treatments to achieve fully printed infrared photodiodes.