Photocrosslinkable Zwitterionic Ligands for Perovskite Nanocrystals: Self‐Assembly and High‐Resolution Direct Patterning

Abstract

Perovskite nanocrystals (PNCs) are attractive photoactive materials in various optoelectronic devices including light‐emitting diodes, solar cells, and photodetectors. However, the weakly bound surface ligands on PNCs reduce colloidal stability and cause film formation and patterning difficulties, severely restricting their practical applications. Herein, a rationally designed photocrosslinkable zwitterionic (PZ) ligand is introduced to obtain directly patternable CsPbBr3 PNCs with enhanced colloidal stability, optical properties, and self‐assembly propensity. The PZ ligands strongly interact with the pre‐synthesized PNCs in solution, substantially replacing the original capping ligands and effectively passivating surface defects. This surface engineering induces strong electrostatic interactions between the PNCs, enabling the fabrication of densely packed CsPbBr3 PNC films. Furthermore, the methacrylate group of the PZ ligands serves as a bridge for active radical propagation in the ligand shells around the PNCs upon UV exposure. Accordingly, high‐resolution direct photopatterning can be achieved through ligand crosslinking, and the resulting PNC patterns (minimum line spacing of 4 µm) maintain optical stability for over 2 weeks. Therefore, this study demonstrates that a tailored ligand design strategy enables the simultaneous achievement of high colloidal stability, optical properties, photopatternability, and self‐assembly propensity and has considerable potential to be extended to other PNC materials.

Real-Time In Situ Observation of CsPbBr3 Perovskite Nanoplatelets Transforming into Nanosheets

“…We attribute this to the random merging paths originated from the different orientations of the initial ribbons, the changes in their local distribution, and their related distances, as it occurs in nanocubes, but also due to the reduced mobility of the NPLs in the substrate. Therefore, to achieve control over the final morphology of the transformed NCs, we foresee three strategies: (i) control over the initial NPL density to favor the formation of uniform films from single ribbon layers via solution-based processes; , (ii) templating the initial orientation of ribbons into the desired configuration to favor one specific merging path; − and (iii) ligand engineering to control the distance between initial ribbons and their orientation. , …”

“…Therefore, to achieve control over the final morphology of the transformed NCs, we foresee three strategies: (i) control over the initial NPL density to favor the formation of uniform films from single ribbon layers via solution-based processes; 25,38 (ii) templating the initial orientation of ribbons into the desired configuration to favor one specific merging path; 40−42 and (iii) ligand engineering to control the distance between initial ribbons and their orientation. 43,44 To detail the atomic merging of the objects, we performed a high-resolution TEM analysis of the resulting nanosheets. Contrary to the spontaneous transformation at room temperature and solution where the dominant defects are RP planar faults, 12 we often observe grain boundaries and, in a few cases, RP planar faults.…”

Surface engineering in CsPbX3 quantum dots: from materials to solar cells

“…Other short ligands with stronger interactions with PQDs should be explored. For example, the zwitterionic ligand 92–94 can tightly bound with the PQDs via the chelate effect, while the co-occurrences of cationic and anionic groups can prevent the external neutralization surroundings of PQDs, and thus enhance the structural durability of PQD films. Therefore, zwitterionic ligands should be further explored for application in solar cells.…”

“…Another family of X-type ligands that has received much attention is zwitterionic (or bidentate) ligands, in which the two functional groups with negative and positive charges simultaneously bind to the X-site and A-site, respectively. 61,62,92–94 The long-chain zwitterionic ligands include sulfabetaine, phosphocholine, and γ-amino acid92 (Fig. 8c).…”

Defects in lead halide perovskite light-emitting diodes under electric field: from behavior to passivation strategies

“…188 The strategic selection of functional groups allows for the design of photocrosslinkable zwitterionic ligands, thereby enabling the fabrication of directly patternable PNCs. 189…”