Efficient charge extraction in lead halide perovskite
nanocrystals
is frequently sought-after and probed using various probe molecules.
Often ignored, the chemical bonding of the molecules to the perovskite’s
surface, as dictated by the terminal anchoring functional group, can
have implications on the excited-state interactions between perovskite
nanocrystals and the charge-shuttling molecules. Considering the remarkability
of the recent work on ferrocene-based molecules in allowing charge
transfer in perovskite nanocrystals, we have employed ferrocene molecule
functionalized with various functional groups to understand the binding
and charge-transfer process at the interface of the perovskite nanocrystal
and the redox relay molecule. We evidenced that the charge transfer
enhanced with enhancement in binding, as validated by the association
constant evaluated as high as 1.71 × 107 M–1. In particular, the −COOH and −NMe2 functional
groups led to the efficient quenching of photoluminescence (PL) emission
and a decrease in photoluminescence lifetime than the other functional
group analogues, showing their feasibility in charge transfer studies.
More importantly, the −NMe2 functional group indicated
passivation of the defects on the perovskite surface, attributed to
the interaction between the lone pair of nitrogen and the undercoordinated
surface Pb2+ cations. This was also evident in the transient
absorption spectra, where the excited-state interaction could be analyzed
better. This work opens avenues for exploring anchoring moieties in
facilitating charge transfer across the perovskite interface, thus
impacting its photocatalytic applications.