Electrical characterization of solid-state heterojunctions between PEDOT:PSS and an anionic polyelectrolyte

Stable organic heterojunctions are developed by deposition of the anionic polyelectrolyte poly(4-lithium styrenesulfonic acid) (LiPSSA) on the top of poly(3,4-ethylendioxythiophene)/poly(styrenesulfonate) (PEDOT:PSS) films. The electrical response of the heterojunctions to triangular voltage pulses in the range between −5 and +5 V is characterized by hysteresis phenomena, observed for hundreds of cycles with low distortions, at scan rates between 1 and 100 mV/s. The hysteresis is ascribed to the occurrence of redox transitions, evidenced by the presence of well-defined peaks in the current–voltage characteristics. The electrical behaviour of the PEDOT:PSS/LiPSSA devices is found to be mainly capacitive, and show humidity-sensitive functionality, demonstrated by the gradual and reversible increase of the area subtended by the J−V cycles as the relative humidity increases.