Understanding the driving force for solution molecular doping

Sequential solution doping is a processing technique that allows a conjugated polymer film to be doped from a solvent that will not dissolve the polymer. We present here a method to predict the film doping level in cm-3 from the solution concentration used to dope the film. We show using four polymers and three different and newly synthesized dopants that the doping level can me modeled using a simple Langmuir isotherm. In addition, analysis of the UV/vis spectra shows filling of the density of states. Polymers with a sharper band edge demonstrate much high conductivity for the same hole density. We analyze a series of DPP polymers and show how the polymer order changes as a function of the doping level. A second recent discovery is that the anion in sequentially doped films can be exchanged with another anion after doping. This means that the reactive molecule used to doped the polymer can be removed and replaced with a different ion that is not reactive. We present a multi-ion Langmuir isotherm model and show that the film doping level in mixed ion solutions can also be predicted.