Studies on switching of J and H aggregates in Donor-Acceptor molecular materials
The aggregation of molecular materials plays a central role in determining their functional properties. In the aggregated state, conjugated chromophores may exhibit enhanced emission, in comparison to their dilute solution. The studies described in this thesis is aimed towards understanding the dynamic behaviour of aggregates (H and J type) in donor-acceptor based -conjugated chromophores. We discuss the synthesis and characterization of three diketopyrrolopyrrole (DPP) based chromophores and their optical properties in solution and thin fi lm. The H and J type aggregates were identi fied by temperature dependence photoluminescence studies. The observation of both H and J aggregates in thin fi lms (pure and with host) of one of the DPP derivatives are corroborated by computational investigations of coulombic coupling between the monomers. By varying the shearing angle between the monomers in the crystal geometry, we nd that both the type of aggregates can exist, in line with the different temperature-dependent intensity ratio plots.