Controlling the particle size of aqueous conjugated polymer colloids and impact on transistor performance

Abstract

Herein, aqueous suspensions of poly (3-hexylthiophene) (P3HT) colloids with tunable particle size were fabricated using a miniemulsion process followed by solvent evaporation. The effects of solvent evaporation temperature, sonication time and surfactant amount on colloid properties and field effect transistor performance were investigated. The particle size distribution and morphology of the colloids were characterized by dynamic light scattering and atomic force microscopy. It was found that increasing solvent evaporation temperature leads to larger particle size; longer sonication leads to smaller particle size and careful selection of these variables along with controlled surfactant amount can be used to tune colloid sizes. Organic field-effect transistors (FETs) prepared using P3HT colloids displayed increasing hole mobility and decreasing threshold voltage as the colloidal particle size decreased. The trend in performance can be explained by considering the geometric factors governing carrier density and carrier transport.