Temperature-dependent kinetics of printed polymer light-emitting electrochemical cells

The thermal activation energy for ion transport and related junction formation in a polymer light-emitting electrochemical cell (LEC) has been determined by measuring the transient behavior of light emission as a function of temperature from 257 K to 297 K. We find the initial time derivative of the light intensity to have an Arrhenius temperature dependence, with an activation energy of 1.6 eV. Our devices utilize a flourene-based polymer emitter which fluoresces at red/near-infrared wavelengths. The polymer matrix includes phenyl alkoxy-substituted PPV and an electrolyte/dopant system based on both solid polymer and ionic liquid dopants. Transient measurements of current and light emission have been used to capture the kinetics of both junction formation and junction decay and to measure variations in optical external quantum efficiency during device turn-on.