(393ap) Layer-by-Layer Assembly of Gel Particles for Polymer Solar Cell Applications
Aqueous dispersions of colloidal gel particles containing poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) serve as solution-processable inks for active layers in polymer solar cells. Bulk P3HT organogels containing PCBM have been emulsified into water to produce sub-micrometer sized gel particles that are stabilized with cetyltrimethylammonium bromide (CTAB). Excess CTAB has been dialyzed from these solutions to form stable, positively charged gel particles. Glass substrates coated with tin-doped indium oxide (ITO) and with poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) have been dipped into these coating solutions, and the kinetics of particle adsorption has been characterized using UV-Visible Spectroscopy. The resultant nanoparticle films have been characterized using atomic force microscopy (AFM), scanning electron microscopy (SEM), and optical microscopy. Presented here is the optimization of coating solution characteristics which maximize P3HT/PCBM gel particle surface coverage on PEDOT:PSS films. Work is ongoing to demonstrate completed solar cells using this approach. These coatings demonstrate the utility of using aqueous processing for the development of polymer solar cells and this method provides a platform for the development of coatings that incorporate lower band gap conjugated polymers.