Absorbance and fluorescence studies on porphyrin Nanostructures (pnr) as light harvesters in dye sensitized solar cells

Abstract

Porphyrin nanorods (PNR) were fabricated by electrostatic self-assembly of two oppositely charge molecules and the compounds used were free base meso-tetra-(4-sulphonatephenyl) porphyrin (H₂TPPS₄⁴) and metallo meso-tetra (4-N-methylpyridyl) porphyrin (MTMPyP⁴⁺) (M = Sn, Mn, Co, In). The aim of this work was to study some photophysical properties of PNR for application as light harvester in dye sensitized solar cells. These properties included absorbance, fluorescence, and fluorescence quantum yield and lifetime. The results of Transmission Electron Microscope (TEM) images showed the formation of nanorods. Electronic Spectra of the PNR revealed J-aggregation bands at 492 nm and accompanied by a band at 712 nm. All the porphyrin nanostructures produced fluorescence at 670 nm when excited at 430 nm and each spectrum had a hidden band at 730 nm. The fluorescence quantum yields were low but deconvolution of the bi-exponential decay curves showed the existence of two species with lifetimes of ~3 ns and ~200 ps.

 Keywords: Porphyrin, Nanorods, Fluorescence, Fluorescence Quantum Yield, Lifetimes, J-aggregates