Tuning Charge-Separated State Lifetimes in Perovskite Nanocrystal-Perylenediimide Hybrids

Abstract

To surface engineer CsPbBr3 nanocrystals (NCs), the use of functional perylenediimides (PDIs) featuring carboxylic acids of different spacer lengths afforded hybrid materials such as NC@PDI-Ph (phenyl spacer) and NC@PDI-PhPr (phenylpropyl spacer). Properties that are not seen by the individual components, are investigated by an arsenal of steady-state and time-resolved techniques. These ranged from hotoluminescence (PL) to ultrafast transient absorption spectroscopy (TAS) combined with global target analyses. Herein, charge separation from NCs to the electron-accepting PDIs upon photoexcitation of either the NC or PDI unities is evidenced. Remarkable is not only the lifetime of the charge carriers, which is on the time scale of microseconds, that is, 34 and 63 μs for NC@PDI-Ph and NC@PDI-PhPr, respectively, but also the control over their lifetimes through tuning phenylversus phenylpropyl-spacer length. These findings are of relevance to solar energy conversion, in general, and perovskite-based devices, in particular.