High-Fidelity\nPick-and-Place\nTransfer Printing of\nColloidal Quantum Dot Pixel Arrays via a Composite Stamp

Transfer\nprinting can pattern emissive colloidal quantum\ndot (CQD)\narrays with ultrahigh pixel density. However, the most used pick-and-place\nmethod has difficulty in achieving high pattern fidelity. Here, we\nreport that the regularly used single-composite stamps cannot combine\na low deformation rate and conformal contact, leading to the challenge.\nIn response, we propose a composite stamp for the CQD transfer. Stacked\nwith PDMS of different mechanical parameters, the composite stamp\noutperforms the single-component stamp composed of soft PDMS (Sylgard184)\nin deformation resistance and exhibits substantially higher contact\nconformality than that composed of harder PDMS. As a result, the composite\nstamp exhibits a 3.21-fold enhancement in transfer yield, delivering\na pattern fidelity of 94.0% with a pixel diameter of 1.78 μm\nand a pixel density of 6350 per inch. The pick-and-place process also\nproduces quantum dot light-emitting diode arrays with the same pattern\nand reasonable electroluminescence performance. This method provides\ninsight into improving CQD arrays’ pattern quality.