Engineering Ultrahigh-Resolution Quantum Dot Light-Emitting Diodes through Stretch-Assisted Transfer Printing.

High-resolution quantum-dot light-emitting diodes (QLEDs) are pivotal for the development of next-generation displays. While transfer printing is effective for fabricating high-resolution QLEDs with small pixels, accurately transferring nanoscale patterns with narrow spacing and gaps remains a challenge, limiting achievable pixel densities. Here, we report a robust stretch-assisted transfer printing strategy for fabricating QLEDs with ultrahigh pixel density. This method overcomes the challenge of transferring nanoscale patterns with narrow spacing and gaps by temporarily expanding feature spacing via applied strain. Efficient QD transfer is achieved, and upon strain release, the spacing contracts to form ultrahigh-resolution nanopatterns. As a result, red, green, and blue QD nanopatterns with an ultrahigh resolution of 33,400 pixels per inch (PPI) and a record-minimum gap of 270 nm are achieved. Thanks to the closely packed QD nanopatterns, leakage current is effectively suppressed, enabling the fabrication of high-performance, ultrahigh-resolution red QLEDs (33,400 PPI) with an average external quantum efficiency (EQE) of approximately 20.3%. Both green and blue QLEDs show no significant efficiency degradation at these nanoscale dimensions. This work provides an additional route for high-performance, ultrahigh-resolution QLEDs.