Formamidinium Lead Bromide Nanocrystals Doped with In³⁺ and Cl^– for Light-Emitting Applications

In 3+ and Cl – codoping in Formamidinium Lead Bromide (FAPbBr 3 ) nanocrystals (NCs) has been achieved using a hot injection approach. A small contraction in nanocrystal size brought about by codoping is manifested in powder X-ray diffraction, X-ray photoelectron spectroscopy and transmission electron microscopy. Significant modulation of optical properties of NCs with codoping has been unraveled using spectral and temporal photoluminescence (PL) properties. An increase in PL lifetime along with a higher contribution of a longer component in the decay associated spectra (DAS) indicates the role of In 3+ /Cl – dopant states in carrier recombination. Fluorescence Correlation Spectroscopy (FCS) has established the blinking rates to be faster in codoped NCs for λ ex = 400 nm as well as 440 nm. This is attributed to the presence of a higher number of accessible states provided by In 3+ . An anticorrelated Cross Correlation Function (CCF) of excitonic and trap states in Fluorescence Lifetime Correlation Spectroscopy (FLCS) ascertains carrier diffusion between excitonic and trap associated states in FAPbBr 3 . However, after codoping, the strong anticorrelation feature in CCF is lost, implying carrier transfer to an In 3+ dopant state from both of the states. Hence, the mechanism of slowing down of PL decay is explained. The blinking dynamics and carrier diffusion in FAPbBr 3, along with changes due to In 3+ /Cl – codoping studied through FCS and FLCS, reveal the degree of interdependency of recombination pathways. This insight enables the design of more efficient light-emitting devices by tuning carrier diffusion routes. Furthermore, the localization of carriers in dopant states observed here improves the charge separation and carrier transfer efficiency, which is crucial for photocatalytic applications.