Verification of p-n junctions in polymer light-emitting electrochemical cells via electrical characterization

We report micrometer thick sandwich light-emitting electrochemical cells (LECs) based on a blend of poly[5-(2(')-ethylhexyloxy)-2-methoxy-1, 4-phenylene vinylene] and poly(ethylene oxide) complexed with lithium trifluoromethanesulfonate. These LECs exhibit very similar properties as those of thin LECs including bipolar current-voltage characteristics and light emission. Mixing of aluminum nanoparticles into polymer layers improves electroluminescence because of smaller series resistance and larger light-emitting area. Taking series resistance into account, we confirm the operating mechanism of an LEC is the formation of a p-n junction by in situ electrochemical doping via fitting the steady state current-voltage characteristics to the expression for the Shockley model of a p-n diode.