Transfer printing of perovskite nanocrystal self-assembled monolayers via controlled surface wettability†

Lead halide perovskite nanocrystals (LHP NCs) have attracted significant attention as next-generation semiconductor nanomaterials due to their near-unity photoluminescence quantum yields and tunable emission wavelengths. Despite their outstanding optical properties, their instability makes it difficult to apply conventional lithography techniques to LHP NC films, which hinders their application in nano-optoelectronics. To overcome this problem, in this work, we propose solvent- and heat-free contact printing technologies for the transfer and microfabrication of LHP NC self-assembled monolayers, employing viscoelastic stamps and wettability-controlled solid substrates. To proceed with multistep transfer of NC films, it is necessary to control the adhesion force between the NCs and the substrate at each step. There is also another requirement concerning the affinity between LHP NCs and substrates to fabricate a spatially uniform LHP NC self-assembled monolayer by spin-coating. To meet these two requirements, the initial substrates for spin-coating were treated with a mixture of fluoroalkyl and alkyl silanes (with a mixing ratio of 0.85 : 0.15), whereas those for transfer were treated with hexamethyldisilane (HMDS). The micropatterned LHP NC monolayers were successfully fabricated by employing patterned viscoelastic stamps. This approach using a back-to-basics technique provides a simple and reliable process for integrating LHP NCs into advanced nano-optoelectronic devices.