Chemical Doping of Well-Dispersed P3HT Thin-Film Nanowire Networks

We demonstrate the preparation of uniformly distributed poly(3-hexylthiophene) (P3HT) nanowire (NW) networks on a variety of substrates. We studied changes in the optical, electronic, and morphological properties upon sequential doping by 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ) by UV–vis spectroscopy, atomic force microscopy (AFM), Kelvin probe force microscopy (KPFM), and electrical conductivity measurements. At a moderate dopant concentration of 250 μg/mL, the P3HT NW networks retain their morphological features with a clear evolution of an absorption band corresponding to doping products. Higher dopant concentrations (∼1 mg/mL) lead to the accumulation of dopant molecules on the surface of the film, forming "dot-like" features. KPFM measurements show a clear difference in the contact potential difference (CPD) of the P3HT NWs with varying doping concentration regimes. Moreover, an increase in the electrical conductivity by 4 orders of magnitude from 10–5 to 10–1 S/cm is observed after moderate doping, demonstrating that significant doping effects can be achieved for a mostly crystalline phase of P3HT such as its nanowire form.