In-situ monitoring of the solid-state microstructure evolution of polymer:fullerene blend films using field-effect transistors

Organic field-effect transistors (OFETs) are used to investigate the evolution of the solid-state microstructure of blends of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C₆₁-butyric acid methyl ester (PC ₆₁BM) upon annealing. Changes in the measured field-effect mobility of holes and electrons are shown to reveal relevant information about the phase-segregation in this system, which are in agreement with a eutectic phase behavior. Using dual-gate OFETs and in-situ measurements, it is demonstrated that the spatial- and time-dependence of microstructural changes in such polymer:fullerene blend films can also be probed. A percolation-theory-based simulation is carried out to illustrate how phase-segregation in this system is expected to lead to a substantial decrease in the electron conductivity in an OFET channel, in qualitative agreement with experimental results. The evolution of the solid-state microstructure of binary P3HT:PC₆₁BM blend films upon annealing is monitored using field-effect measurements. Changes in the measured hole and electron mobilities are shown to reveal relevant information about the phase-segregation in this system. Using single/dual-gate transistors and in-situ measurements, it is demonstrated that the spatial- and time-dependence of microstructural changes in such polymer:fullerene blend films can be probed.