Executive Summary : | The light emission from a single nanocrystal under continuous excitation turns on and off, is called photoluminescence (PL) intermittency, is commonly known as blinking. The mechanism of PL intermittency in the single nanocrystal is very complex. In nanocrystals (NCs), PL fluctuation is the result of the trapping and de-trapping of the charged carrier by which several non-radiative channels become active. This mechanism involves multiple trapping sites, with an adverse effect on the efficacy of the nanocrystal for optoelectronic applications. Charge carrier dynamics of halide perovskite nanocrystals is a hot research topic, in which there are many uncharted territories. Bulk of the work so far has focused on undoped lead-based halide perovskites nanocrystal.[1-7] The stability of the nanocrystals and efficient non-radiative channels pose major challenges in the design of strongly emissive perovskite nanocrystals. Therefore, to get efficient device material by reducing non-radiative channels, we have to understand the mechanism of non-radiative decay or/and intermittency. PL blinking or intermittency in a single quantum dot was first observed back in 1996.[8] They have found a characteristic timescale of 0.5 seconds which is not apparent from ensemble average measurement. In the case of ensemble measurements, this blinking or nor-radiative phenomenon can be observed by the loss of efficiency or quantum yield of the material and it is difficult to get information about the mechanism. Thus, the exploration of the blinking mechanism demands a single molecular level investigation over ensemble measurements for the appropriate understanding of the non-radiative processes and their nature. The present proposal intends to generate an in-depth understanding of the non-radiative channels, by probing PL blinking behaviour obtained from a single nanocrystal of doped lead halide and lead-free halide perovskite nanocrystals.
Attempts will be made to propose modifications in synthetic procedures and treatments to make these nanocrystals strongly emissive.
For the exploration of photoluminescence blinking, Fluorescence correlation spectroscopy (FCS) and fluorescence lifetime correlation spectroscopy (FLCS) are very powerful tools which elucidate the dynamics of NCs in the mobilized state with microsecond resolution. |