Nanopixel-emitting arrays represent a significant advance in the field of display technologies, offering the potential for ultra-high resolution and colour fidelity [1]. Our study reports on the fabrication and characterisation of nanometer-scale pixel arrays based on colloidal semiconductor nanocrystals (NCs), in particular using CdSe/CdS core-shell NCs. The arrays fabricated demonstrate a pixel size of 100 nm, which could be a critical milestone in the development of next-generation display devices. The approach used in this study integrates advanced nanofabrication techniques with colloidal chemistry, resulting in an efficient and scalable method for fabricating nanocrystals-based pixel arrays.

The fabrication of these nanopixel-emitting arrays involves several steps, starting with the deposition of a 100 nm thick indium tin oxide (ITO) layer on a glass coverslip substrate. This is followed by the spin-coating of a ZnO layer, which acts as an electron transport layer, and the subsequent deposition of polymethyl methacrylate (PMMA), which acts as a resist layer for lithographic patterning. Electron beam lithography (EBL) was used to pattern matrices of nanoholes approximately 100 nm in diameter. These nanoholes are spaced 2 μm apart both vertically and horizontally, forming a well-defined array structure. The use of EBL allows precise control over the pattern dimensions and the spatial distribution of the nanoholes, which are critical parameters for the performance of the nanocrystal emitters. After EBL patterning, a dilute solution of colloidal NCs consisting of a mixture of water and ethanol was drop cast onto the nanopatterned areas of the substrate. The solution was allowed to dry at a controlled temperature of 45°C to ensure uniform distribution and optimal filling of the nanoholes.

This fabrication process follows a similar procedure reported in our recent work [2], but by changing the surface ligands on the colloidal NCs and tuning the deposition parameters, we were able to completely fill the nanoholes with NCs. To evaluate this result, we first inspected the arrays by scanning electron microscopy (SEM) and then realised photoluminescence (PL) maps to measure the optical performance of the individual nanopixels within the arrays. The PL maps generated from these measurements showed a high filling efficiency of the nanoholes with NCs, demonstrating the effectiveness of the fabrication process.

In conclusion, this work presents a novel approach to the fabrication of nanopixel-emitting arrays using colloidal nanocrystals, with significant implications for the future of display technology. The combination of precise nanofabrication techniques and the unique optical properties of NCs enables the realisation of pixel arrays with nanoscale dimensions, paving the way for the development of ultra-high resolution displays. Future research will focus on the realization of the full light emitting diode (LED) structure to electrically excite the nanopixel emitting arrays and compare the resulting electroluminescence with the already measured photoluminescence.