CH3NH3PbBr3 perovskite quantum dots (PQDs) are synthesized using (3-aminopropyl)triethoxysilane (APTES) in conjunction with four different linear alkyl phosphonic acids (PAs) as capping ligands. The structures of the PQDs are characterized using XRD, TEM, HRTEM, Raman and FTIR spectroscopy, while their electronic and optical properties studied using XPS, UV-Vis and photoluminescence (PL) spectroscopy, and time-resolved photoluminescence (TRPL). The PQDs of different sizes have a high PL quantum yield (QY), indicative of low density of bandgap trap states and effective surface passivation. FTIR and Raman spectra reveal that the deprotonated PAs passivate the surface of PQDs through the phosphate group. XPS spectra suggest that the surface defects due to Pb2+ and CH3NH3+ are passivated by the R–PO32- or the R–PO2(OH)- group while defects due to Br- are passivated by the R–NH3+ group. Furthermore, the CH3NH3PbBr3 PQDs become more stable and have bluer absorption due to decreasing size when the chain length of linear alkyl PAs is decreased. This is attributed to better passivation with shorter PAs, possibly due to better solubility and less steric hindrance. This study demonstrates the PAs, in conjunction with APTES, are highly effective in passivating PQDs with multiple surface defects through primarily ionic bonding.

Surface passivation of lead halide perovskite quantum dots based on synergistic effect between phosphonic acid and (3-aminopropyl)triethoxysilane

2019 Spring National Meeting

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