Confocal Microscope Studies of Polycyclic Aromatic Hydrocarbons and Semiconductor Single Nanoparticles

With the rapid development of fluorescence microscopy, one could obtain an in-depth investigation of conjugated material morphology and photophysical properties in a solid state. The trimeric perfluoro-ortho-phenylene mercury compound (Hg₃) and polycyclic aromatic hydrocarbon (PAH) derivatives show unique supramolecular interactions in solution and solid-state. Inspired by the previous work of Gabbai and coworkers, we found that the addition of Hg₃ to alkyl-substituted derivatives of hexa-peri-hexabenzocoronene (HBC) solution leads to a noticeable red-shifting of the maximum absorbance of the HBC chromophore and a dramatic decrease in HBC luminescence as well as an appearance of phosphorescence from the Hg triad (c.a. 577 and 625 nm), which is consistent with the formation of aggregates. In transient absorption spectroscopy, the HBC-Hg₃ complex reveals the triplet localizes on the HBC chromophore. A confocal laser scanning microscope is used to characterize the morphology and lifetime distributions of the HBC-Hg₃ aggregates.

Inorganic perovskite materials have recently attracted enormous attention because of their high absorption coefficients and facile solution processability. However, the charge transfer (CT) efficiency between light harvesters and hole/electron transporting materials is vital in improving the power conversion efficiency of perovskite photovoltaic devices. To further understand the interfacial dynamic process and quenching mechanism, a deeper investigation and further study of the electron transfer reaction between the excited perovskite nanocrystals and electron acceptors at the single-particle level is required. From the dynamical and statistical study, we found that by adding a quencher, the single nanocrystals are prone to localized at the off state, corresponding to a lower lifetime. Furthermore, single nanoparticle studies reveal how the trap state concentrations control the perovskite exciton dynamics and the fluorescence quenching limited by the nonradiative photoionization process.