Direct Optical Lithography of CsPbX₃ Nanocrystals via Photoinduced Ligand Cleavage with Postpatterning Chemical Modification and Electronic Coupling

Abstract

Microscale patterning of solution-processed nanomaterials is important for integration in functional devices. Colloidal lead halide perovskite (LHP) nanocrystals (NCs) can be particularly challenging to pattern due to their incompatibility with polar solvents and lability of surface ligands. Here, we introduce a direct photopatterning approach for LHP NCs through the binding and subsequent cleavage of a photosensitive oxime sulfonate ester (−CN–OSOO−). The photosensitizer binds to the NCs through its sulfonate group and is cleaved at the N–O bond during photoirradiation with 405 nm light. This bond cleavage decreases the solubility of the NCs, which allows patterns to emerge upon development with toluene. Postpatterning ligand exchange results in photoluminescence quantum yields of up to 79%, while anion exchange provides tunability in the emission wavelength. The patterned NC films show photoconductive behavior, demonstrating that good electrical contact between the NCs can be established.

Direct optical patterning of perovskite nanocrystals with ligand cross-linkers

“…Note that anion exchange reaction readily occurs when NCs with different anions are in physical contact during the multilayered patterning process. This was also observed in a recent report on perovskite NC patterning with photocleavable ligands ( 28 ). As DOPPLCER is generally applicable to various NCs, this issue can be addressed by using NCs with the same anion but different emission colors.…”

“…These assumptions, however, need to be verified with further studies. Nonetheless, films after DOPPLCER still maintain an absolute PLQY of 38%, which compares favorably with those patterned by photocleavable oxime sulfonate ester ligands (PLQY, <5%) ( 28 ). Shorter averaged lifetime from time-resolved PL measurements ( Fig.…”

“…However, it typically entails ligand exchange process and polar solvents, which can structurally and/or optically damage perovskite NCs. Note that a very recent work addressed these issues by using oxime sulfonate esters as photosensitive ligands and toluene as the solvent for perovskite NCs ( 28 ). Complementing the design of short, photodecomposable ligands, polymeric ligands with cross-linkable fragments also allow direct patterning of perovskite NCs via cycloaddition, polymerization, and other pathways ( 29 ).…”

Direct patterning of colloidal quantum dots with adaptable dual-ligand surface

“…Direct photolithography, a method in which light exposure directly induces solubility change in QD layers, is considered as an effective solution to mitigate the aforementioned issues 11,20−23 . Several approaches have been proposed, such as the detachment or decomposition of ligands upon UV irradiation [20][21][22][23] . Yet, corrosive chemicals (e.g., acid) are produced as by-products from these reactions, deteriorating the luminescence e ciency of QDs 20,22 .…”

Recent Patterning Methods for Halide Perovskite Nanoparticles

“…Therefore, complex patterning can be formed even with perovskite with sensitive stability, and many studies are being conducted. [162][163][164] In addition, methods of patterning by changing the composition and properties of perovskite materials, such as replacing and controlling the ligands of perovskite to increase stability or forming a photo-crosslinked ligand to pattern through light, [165] are also being studied as one of the future patterning technologies. We propose a perspective on optoelectrical devices made of patterned perovskites and their patterning methods.…”