Photophysics, TiO2 sensitization and photovoltaic performance of Zn-ProtoporphyrinIX

Abstract

Chlorophylls are playing an important role in natural photosynthesis. Hence, in the present investigation, a chlorophyll analogue Zn-Protoporphyrin IX (ZnPPIX) was selected for dye sensitized solar cell applications. The properties of ZnPPIX were fully investigated by optical spectroscopy, attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), density functional theory (DFT) calculations, electrochemical and photovoltaic measurements. The optical and electrochemical HOMO-LUMO gaps were consistent with those estimated by PBE functional. The nature of the binding of ZnPPIX onto the TiO2 surface was investigated using ATR-FTIR and XPS measurements. The amount of adsorbed ZnPPIX on TiO2 surface was reasonably fit using the Langmuir adsorption isotherm, with a binding constant value of 25,800 M−1. The power conversion efficiency of ZnPPIX is smaller than those of reference cell under the optimized conditions (η = 0.6% for ZnPPIX; η = 6.3% for N3).