Polar-Resistance Perovskite Quantum Dots Based on Silane Network Passivation with Pb-S Interaction Generated via X-Type Ligand Exchange

In recent years, lead halide perovskite quantum dots (PQDs) have shown the advantages of optical materials, such as narrow half width (FWHM), wide wavelength range, high quantum yield, superior defect tolerance and absorption coefficient characteristics. [1,2] However, perovskite quantum dots (PQDs) are still the perovskite structure is highly susceptible to humidity and polar solvents, and exposure leads to a rapid loss of optical properties, structural integrity, and particle stability. [3,4] We fabricated silane network-passivated perovskite quantum dots (PQDs) by adding silane ligands, the end groups of which consist of thiol groups, to induce an X-type ligand exchange reaction. This suggests that the number of PQD surface vacancies and binding energy is determined by the 1) strong Pb–S interactions in perovskite and 2) passivation effect. Thus, we were able to induce the formation of a network between the crystal structures of Cs-type PQDs; we subsequently evaluated their optical efficiency and chemical stability in detail. For comparison, PQDs were manufactured by introducing a silane material with the same chemical structure and an amino group as the functional group. We detail the differences resulting from the bonding of thiol and amino groups (i.e., QD@MPTMS, QD@APTMS). Rapid particle aggregation was observed in QD@APTMS, whereas QD@MPTMS exhibited excellent performance and dispersibility owing to the network between PQDs. Enhanced Pb–S interaction as a result of thiol-based ligand introduction was confirmed by applying X-ray photoelectron spectroscopy analysis, which demonstrated that the ligand influenced the binding energy of the perovskite structure. These results, as well as analysis of the passivation effect, were also confirmed by conducting water- and polar solvent-resistance tests. Furthermore, the particle size, quantum yield, life span, interfacial properties, and characteristics of the device into which each type of PQD was integrated were significantly different. Moreover, when we confirmed the polar stability by injecting acetone, a polar solvent vulnerable to perovskite up to 2 ml, QD@APTMS and QD@MPTMS maintained luminescence. However, further PL analysis revealed QD@APTMS and QD@MPTMS to have luminescence intensities that were 21% and 63.5% of the original values, respectively, even though the amount of acetone injected was 2 times. The results indicate that the MPTMS silane material is a ligand that minimizes and supplements perovskite surface vacancies and defects of particles.