High-Fidelity Pick-and-Place Transfer Printing of Colloidal Quantum Dot Pixel Arrays via a Composite Stamp.

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