Hybrid polymer solar cells: From the role colloid science could play in bringing deployment closer to a study of factors affecting the stability of non-aqueous ZnO dispersions

The development and deployment of large-scale, cost-effective, renewable energy is becoming increasingly important. This article aims to show how colloid and interface science could enable major power conversion efficiency improvements for hybrid polymer solar cells. These solar cells contain inorganic nanoparticles (e.g., CdSe, ZnO or PbS) blended with semiconducting polymers. We also present experimental data concerning the dispersion stability of ZnO nanoparticles (nanocrystals and nanorods) under conditions similar to those used for photoactive layer preparation within hybrid solar cells. The dispersion stability was probed using turbidity, electrokinetic sonic amplitude and optical microscopy measurements. The data indicate that the improved stability of ZnO dispersions that has been reported, but not explained, in co-solvent blends containing methanol (MeOH) is due to physisorption of MeOH to the ZnO surface. Furthermore, turbidity data also suggest that depletion aggregation of ZnO nanoparticles is likely under conditions used to prepare hybrid solar cells. The article concludes with suggestions for future colloidal studies that may enable improvements of the power conversion efficiencies for hybrid polymer solar cells.