It can be seen that the ON/OFF ratio undergoes a slight decline in the beginning and remains at about 103 during the rest time of the test, indicative of a reliable memory retention performance. MLN0128 The little degradation of the ON/OFF ratio is mainly from the decrease of the ON state current, which is probably associated with the unstable interfacial contact between the surfaces of the organic matrix and Ag2S nanocrystals [5]. To test the reproducibility of the devices, a programmed voltage sequence of 10, −2, −10, −2 V was applied to the device circularly to simulate the write-read-erase-read process, and the result is depicted in the inset of Figure 4. The ON/OFF current ratio is more than two

orders of magnitude and the current changes disciplinarily

and reproducibly during the write-read-erase-read Dabrafenib switching sequence. Figure 4 Retention ability of electrically bistable devices under the sweeping voltage of 1 V. The inset shows switching performance of device during a programmed ‘write-read-erase-read’ sweeping sequence. To clearly understand the carrier transport mechanism in the electrically bistable devices, we have fitted the experimental I-V curves in ON and OFF states by using some theoretical models of organic electronics. Figure 5a,b shows the experimental results and the linear fitting for the OFF state in the positive voltage region. As shown in Figure 5a, the experimental I-V curve in the voltage region of 0 to 7 V can be well

fitted by the thermionic emission model (logI∝V 1/2 ), indicating that the current is dominated by the charge injection from the electrodes [21]. However, else when the applied voltage sweeps from 7 to 10 V, the logI-logV characteristics shown in Figure 5b exhibit a large linear slope of 9.2, which is consistent with a trap-controlled space charge limit (TCLC) model (I∝V α , α > 2) [22]. The fitting result indicates that when the applied voltage surpasses V on, the charges will break the energy barrier and can be captured in the traps by the Ag2S nanospheres with an exponential distribution in the forbidden gap. Figure 5 Experimental results (open cycle) and theoretical linear fitting (solid line) of I-V characteristics in positive voltage region. (a) Linear relationship of logI versus logV 1/2 in the voltage region of 0 to 7 V (OFF state); (b) linear fit in double logarithmic scale in the voltage region of 7 to 10 V (OFF state); (c) linear fit in double logarithmic scale at voltage region of 10 to 0 V (ON state). In contrast, the experimental I-V result in ON state can be well described by an ohmic model, which is depicted in Figure 5c. It can be seen that a distinct linear relationship between logI and logV, with a slope of 1.2 in the positive (10 to 0 V) region. The theoretical fitting illustrates that the current of the device is approximately proportional to the applied voltages, which is close to the Ohmic law (I∝V) [23].