2.7 Ionic movement

Both \(\mathtt{\require{color}{\color[rgb]{0.000000000000000,0.500000000000000,0.500000000000000} SimSS}}\) and \(\mathtt{\require{color}{\color[rgb]{0.000000000000000,0.500000000000000,0.500000000000000} ZimT}}\) include the effects of ionic species. Their motion is described by the same drift-diffusion equations that are used for electrons and holes, yet without the possibility of leaving or entering the device through the electrodes, or via generation/recombination processes. In other words, their total number is conserved throughout the simulation.

The properties that define ionic movement are specified per layer. The concentrations and mobilities of anions and cations are set via \(\mathtt{\require{color}{\color[rgb]{0.000000000000000,0.500000000000000,0.500000000000000} N\_ anion}}\), \(\mathtt{\require{color}{\color[rgb]{0.000000000000000,0.500000000000000,0.500000000000000} N\_ cation}}\) and \(\mathtt{\require{color}{\color[rgb]{0.000000000000000,0.500000000000000,0.500000000000000} mu\_ anion}}\), \(\mathtt{\require{color}{\color[rgb]{0.000000000000000,0.500000000000000,0.500000000000000} mu\_ cation}}\), respectively. Whether ions can move into adjacent layers or not is set by \(\mathtt{\require{color}{\color[rgb]{0.000000000000000,0.500000000000000,0.500000000000000} IonsMayEnter}}\). As there can be multiple (adjacent) layers where ions can or cannot enter, we define ionic regions. This is a group of adjacent layers that can accept ions. Different ionic regions are separated by layers that cannot accept ions or by the contacts. An example is illustrated in figure 2.3.