Implication of porous TiO2 nanoparticles in PEDOT:PSS photovoltaic devices

Abstract

Recent developments in the synthesis of mesoporous nanocrystalline titanium oxide (TiO2) have opened up several new opportunities in the construction of efficient photovoltaic (PV) cells. In this chapter, we describe principles involved in the construction of organic photovoltaic cell and the influence of the main parameters for the case of PEDOT:PSS polymers. At the outset different architectures of the PEDOT:PSS photovoltaics are described and later incorporation of the TiO2 nanoparticles in their architectures is carefully considered. A special attention is given to the technique of photovoltaic cell preparation and the basic principles of their functionality. A significant emphasis has been devoted to the current-voltage characteristics of photovoltaic cells, thus constructed with and without nanocrystalline TiO2, as well as to the ways it can be further improved. We also describe the synthesis of mesoporous TiO2 nanoparticles using titanium alkoxides as precursor and polyethylene glycol (PEG) of different molecular mass as templating agent to induce mesoporosity. The interaction of PEG with titanium alkoxides in polar and nonpolar solvents was studied in detail by macro-Raman spectroscopy, solid-state NMR and MALDI-TOF-MS. The removal of PEG as well as the crystallization process was obtained by hot water treatment at low temperature (900C). The mesoporosity was retained after further calcination up to 5000C. Porosity, morphology, and microstructures of the resultant products were characterized by SEM, nitrogen adsorption-desorption measurements, micro-Raman spectroscopy and XRD. The mesostructure of the TiO2 particles facilitates enhanced transport of electrons, resulting in improved photovoltaic efficiency. Influence of TiO2 nanoparticles on the photovoltaic efficiency of the ITO/PEDOT: PSS/fluorine copolymers/polythiophene:TiO2/Al architecture is analyzed. Influence of TiO2 NP on the principal parameters of different PV architecture is discussed. The analysis of the efficiency is performed using both experimental and theoretical quantum chemical approach.