Nondestructive Direct Photolithography for Patterning Quantum Dot Films by Atomic Layer Deposition of ZnO

Colloidal quantum dot-based light-emitting diodes (QD-LEDs) are one of the potential future self-emissive displays owing to their large-scale solution-processibility and high color purity. For the industrial application of QD-LEDs, high-performance QD-LED and high-resolution patterning of quantum dot (QD) films are required. Photolithography is an ideal tool for patterning QD films. Previously, the high-resolution patterning of QD films using direct photolithography by ultra-thin atomic layer deposition of ZnO on the QD surface is reported. The patterning process is acceptable for Cd-based QD films, but the photoresist severely deteriorates the photoluminescence (PL) intensity of InP-based QD films owing to the presence of sulfonic groups in the photoactive compound. Herein, a non-destructive direct photolithography process for QD film patterning using a negative photoresist that does not affect the PL intensities of Cd- and InP-based QD films is reported. The effect of the photoresist is also verified by a PL lifetime study. Extremely bright Cd- and InP-based QD films are successfully patterned using a softer photoresist, and micropatterning of InP-based QD films is reported for the first time in this work using photolithography. A QD electroluminescence device is also successfully fabricated using the patterning method.