PREPARATION AND CHARACTERISATION OF PERYLENE DIIMIDE THIN FILMS

Abstract

Perylene tetracarboxylic diimide (PDI) molecules are a class of organic dyes that exhibit excellent absorptivity, chemical and thermal stability and show n-type semiconductor properties. The electron-withdrawing nature and significant charge transfer properties make PDIs ideal molecules for the development of photovoltaic cell devices, organic field effect transistors and organic light-emitting diodes. In this thesis, we have studied three PDI derivatives PDI-C1 (N, N'-dimethyl-3,4,9,10-perylenedicarboximide), PDI-C5 (N, N' dipentyl-3,4,9,10- perylene dicarboximide), PDI-C8 (N, N'-dioctyl-3,4,9,10-perylene dicarboximide). I have prepared different PDI derivatives solutions in dichloromethane (DCM) and prepared their thin films with the help of thermal evaporator method. The characterisation of their solution and thin film were done by UV-Vis absorption, fluorescence spectroscopy, scanning electron microscopy (SEM), thin film X-ray diffraction (XRD), Time correlated single photon counting (TCSPC) and Transient absorption (TA). I have observed that the aggregation occurs in the thin film state. Moreover, theoretically it has been suggested that the aggregation decreases the energy levels of the S1 state and matches the energetic requirement of singlet fission, i.e. E(S1)=2E(T1), which makes them suitable candidate for singlet fission process. I believe that upon incorporating these kinds of materials to the solar cells, the efficiency of the solar cells can be significantly enhances.