Investigation of Nanostructured-Polymer Blend Solar Cells

Abstract

Solar cells based on organic photoconductive thin films have shown to possess attributes that enable them to compete effectively with modules based on crystalline silicon. It is exp ected that these attributes will allow realization of a lower $/W p cost figure for organic solar cells compared to crystalline silicon. These attributes are large optical absorption coefficient, high reliability, high efficiency and lower materials costs. The cost reductions and reliability of thin film technologies result from monolithic integration which requires fewer processing steps, avoids expensive crystal growing in large areas, the handling of fragile wafers and their discrete interconnection. Nano structure -polymer blend solar cells generally have the following structure : indium tin oxide ( ITO )/active polymer /metal electrode , where the active polymer layer is composed of a weak donor polymer doped with nanostructures , such as carbon nanotubes, that act as electron acceptors. We have investigated the material properties of the various layers of nanostructure -polymer blend solar cells . Single wall carbon nanotubes (SWNT) were fabricated by a laser vaporization method and characterized by transmission electron microscopy . The interface between metal electrode and the polymer layer was investigated by sputtering two types of metals, Au and Ag, on poly(3 -octylthiophene) (P3OT). The metal/polymer interface was s tudied by focus ion beam (FIB) and seconda ry ion mass spectroscopy (SIMS). A design of experiment (DOE) study was implemented to determine the processing parameters that had the most significant effect on the film properties of poly(3,4 -ethylenedioxythiophene) doped with polystyrenesulfonate (PED OT:PSS) spin coated on ITO by looking at the relationship between controllable factors such as spin coating speed, solution concentration, anneal time, anneal temperature and the resulting % roughness of the films. It was found that a broad interfacial la yer is present between the metal and the polymer layer and the DOE showed that solution concentration had the most effect on the % roughness.