A Fully Printed Heterojunction Based on PEDOT:PSS and ZnO With Memristive Behavior

This work reports the fabrication and electrical characterization of fully inkjet-printed Ag/PEDOT:PSS/zinc oxide (ZnO) heterojunction devices on flexible polyimide (Kapton) substrates. All functional layers, including the bottom Ag electrode, p-type PEDOT:PSS, and n-type ZnO, are deposited exclusively by inkjet printing, enabling a scalable and low-temperature additive process compatible with large-area flexible electronics. While PEDOT:PSS/ZnO heterostructures have been widely studied for optoelectronic and diode applications, they are typically realized using partially printed or vacuum-processed layers and are not optimized for memristive operation. Here, we demonstrate that fully printed PEDOT:PSS/ZnO heterojunctions exhibit pronounced rectifying current–voltage ( $I$ – $V$ ) characteristics, a clear threshold for switching, and a stable hysteretic response indicative of memristive behavior. The device response stabilizes after an initial forming cycle and maintains reproducible high and low resistance state (LRS) over repeated voltage sweeps. Furthermore, under voltage pulse sequences, the heterojunction shows short-term potentiation and depression, with the conductance depending on the history of applied pulses, mimicking synaptic plasticity. These results highlight fully inkjet-printed PEDOT:PSS/ZnO heterojunctions on flexible substrates as promising candidates for low-cost, large-area artificial synapses and printed neuromorphic circuits.