Comparison of bipolar and unipolar ionic diodes

Abstract

Nanoporous ionic diodes, as well as devices for manipulating ions and molecules in asolution, have attracted a great deal of interest from researchers in various fields from thefundamental point of view. Ionic diodes allow the ions to be transported in one directionand block the transport in the other. There are two types of diodes that have beenrealized experimentally. A bipolar diode contains a junction between two zonesof the pore walls with positive and negative surface charges. A unipolar diodecontains a zone that is neutral and a zone that is charged. In this paper we discussdifferences in operation of the diodes with a special emphasis on the sensitivity of theirperformance to the lengths of the charged and neutral zones. We also show that abipolar diode offers more asymmetric current–voltage curves than a unipolar diode.