Hybrid Solar Cells

The aim of the project is to characterize organic-inorganic hybrid materials for photovoltaic applications. Hybrid materials combine the unique properties of one or more kinds of inorganic nanoparticles with the film forming properties of polymers. Most of the polymers can be processed from solution at room temperature enabling the manufacturing of large area, flexible and light weight devices. To exploit the full potential for the technological applications of the nanocrystalline materials, it is very important to endow them with good processing attributes. For this purpose, we want to synthesize clusters of nanodimensional inorganic materials such as CuInSe2, CuInS2, which are already utilized photovoltaic materials in their bulk form. The surface of the inorganic cluster will be modified during the synthesis by organic surfactants. The surfactant can alter the dispersion characteristics of the particles by initiating attractive forces with the polymer chains, in which the particles should be homogenously arranged. But also the stability against oxidation and against aggregation can be inhibited by tailoring the surface modification. The shape and doping state of the nanocrystals will be optimized by varying of the synthesis conditions. Blending p-type semiconducting polymers and n-type inorganic semiconductors, we will prepare hybrid solar cells and optimise cell configurations, in their morphology, opto-electronical properties and photovoltaic performance.

During this project we have investigated hybrid solar cells using organic, semiconducting polymers and inorganic semiconductor nanoparticles in layered as well as composite systems. Our studies revealed the following results: a.) The nanoparticle photophysical properties determine the efficiency of the solar cells significantly. The red shifted absorptions extend the operational frequency regime of the hybrid solar cells. b.) The miscibility of hydrophobic organic semiconducting polymers with the hydrophilic inorganic nanoparticles is problematic. Therefore, nanoparticles with compatibilizing ligands are important requirement for the hybrid solar cells. c.) Using nanoparticles as dye sensitiziers in TiOx nanparticle hybrid solar cells one can enhance the efficiency considerably. d.) Using quasi solid state electrolytes reveal much higher power conversion efficiencies in hybrid solar cells as compared to all solid state organic semiconductor used hybrid solar cells.