Double Doping of Semiconducting Polymers Using Ion- Exchange with a Dianion

摘要

The interactions between counterions and electronic carriers in electricallydoped semiconducting polymers are important for delocalization of chargecarriers, electronic conductivity, and thermal stability. The introduction of adianions in semiconducting polymers leads to double doping where there isone counterion for two charge carriers. Double doping minimizes structuraldistortions, but changes the electrostatic interactions between the carriersand counterions. Polymeric ionic liquids (PIL) with croconate dianions arehelpful to investigate the role of the counterion in p-type semiconductingpolymers. PILs prevent diffusion of the cation into the semiconducting polymersduring ion exchange. The redox-active croconate dianions undergo ionexchange with doped semiconducting polymers depending on their ionizationenergy. Croconate dianions are found to reduce doped films of poly(3-hexylthiophene), but undergo ion exchange with a polythiophene with tetraethyleneglycol side chains, P(g42T-T), that has a lower ionization energy. Thecroconate dianion maintains crystalline order in P(g42T-T) and leads to alower activation energy for the electrical conductivity than PF_6~? counterions.The control of the doping level with croconate allows optimization of the thermoelectricperformance of the semiconducting polymer. The thermal stabilityof the doped films of P(g42T-T) is found to depend strongly on the nature ofthe counterion.