Binding Strength-Guided Shuttling of Charge Carriers from Perovskite Nanocrystals to Molecular Acceptors
Siddharth Singh, Diksha Mittal, Vinithra Gurunarayanan, Ankita Sahu, Ramesh Ramapanicker, Vishal Govind Rao
Abstract
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 × 10 7 M –1 . In particular, the −COOH and −NMe 2 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 −NMe 2 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 Pb 2+ 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.