Optical Performance of a Hybrid Nano-Polymer Solar Cell

Solar energy harvesting is one of the most fundamental solutions to the energy crisis; photovoltaics are the best way to achieve it. Organic based photovoltaics have potential for application as a renewable source of energy. It is cost-effective, light weight, simple and economical to fabricate. Introduction of nanomaterials into polymers is very promising for enhancing photovoltaic conversion efficiency and can potentially improve photochemical and environmental stability. The objective of this paper is to investigate the influence of the nanocomposite film morphology on the optical performance of the hybrid nano-polymer solar cell. The efficiency of such hybrid solar cell depends mainly on the exciton dissociation efficiency and charge mobility. The exciton dissociation efficiency can be improved by increasing the interfacial area between the nanoparticles and polymer. Charge mobility can be improved by proper distribution of nanoparticles in polymer to form better percolation path of each material. Both these parameters are strongly dependant on better distribution of nanoparticles in the polymer. The approach used here is the application of star dispersant, specifically designed for conducting polymers. This dispersant will modify the arms of the conducting polymer to have a high affinity towards nanoparticles and provide better distribution. In this paper the influence on the morphology of the solar cell by the use of star dispersant and corresponding improvement in optical properties and performance is analyzed. Subsequent papers will describe the photovoltaic enhancements of such a solar cell. The solar cell structure chosen here is ITO / PEDOT:PSS / P3HT:TiO2 / Al. A number of specimens are prepared with and without introduction of the star-dispersant. For structural characterization, Scanning Electron Microscopy (SEM) is used. Absorption spectrum analysis and Photoluminescence (PL) analysis are performed to characterize the optical properties of the active layer. Structural characterization revealed that with the application of the dispersant, better mixing of the nanoparticles and the polymer can be achieved. This will in turn increase the interface area and improve exciton dissociation. Better PL quenching is observed in the dispersant modified active layer confirming an improved degree of exciton dissociation.© 2007 ASME