Electrical characteristics of light-emitting electrochemical cells based on a wide bandgap polymer

We report on the electrical characteristics of light-emitting electrochemical cells based on a methyl substituted ladder-type poly(paraphenylene) (m-LPPP). Current-voltage (I-V) characteristics and capacitance-voltage (C-V) plots are used to track the formation of the highly conductive contacts, the initial diffusive carrier transport regime, the onset of a net voltage drop across the polymeric bulk, and the final resistive behavior of the device in which carriers are mostly driven by drift. The analysis of the C-V plots reveals a strong increase of the capacitance at the threshold as a signature of the large carrier injection through the contacts and their diffusion through the active layer. From the physical analysis of the device behavior an electrical model is drawn.