A.c. impedance of frozen junction polymer light-emitting electrochemical cells

The structure of the frozen p—i—n junction in polymer light-emitting electrochemical cells (LECs) is studied by measurements of the a.c. impedance of LEC devices. Impedance plots of frozen junction LECs show characteristics that are typical of polymer light-emitting diodes. The data demonstrate the ‘freeze-out’ of ionic mobility. The frequency-independent and voltage-independent capacitance of the frozen junction supports the conclusion that the insulating ‘i’ in the p—i—n junction occupies most of the thickness of the LEC polymer layer.