Colloidal stability of semiconducting nanoparticles dispersed in co-solvent blends: Implications for morphology control within hybrid polymer / nanoparticle solar cells

摘要

Hybrid polymer nanoparticle solar cells contain a light-harvesting photoactive layer composed of semiconducting nanoparticles dispersed within a polymer matrix. We present here a comprehensive study of the effect of colloidal stability upon the morphology of the final spun-cast photoactive layers of model systems which builds on earlier work2. Both ZnO nanocrystals (NCs) and nanorods (NRs) are investigated in the presence of or poly(triarylamine) or poly(thiophene) based conjugated polymers. Dispersion stability is studied using turbidity measurements and film morphology by optical microscopy and AFM. It is shown that cosolvents capable of hydrogen bonding conferred the greatest colloidal stability, and that the stability of the dispersion prior to spin casting has a direct effect upon the morphology of the photoactive layer. Transient absorption spectroscopy studies show that the films with morphologies having the least nanoparticle aggregation gave the highest extents of photogenerated charge dissociation. The results are used to suggest general conditions that may lead to power conversion efficiencies improvements for hybrid solar cells.