Week 3: Meeting supervisor, calculating and understanding

 Today we met our supervisor at her office, and she gave us a review of the structure of organic Schottky carrier diode and a graph of the relationship between voltage V and current I. Figure 1 and figure 2 show the details about the relationship between voltage and the logarithm of current with organic semiconductor of Schottky barrier diode. Also it is necessary to do some related calculations to learn more about this kind of  materials.

Figure 1: The relationship between current and voltage

 For the first graph,the x-axis represents the voltage in volts, and the y-axis represents the logarithm of the current in amperes. It can be seen that this graph can be divided into two parts, there is a decrease line on the left of the y-axis which at on current condition, and there is a increase line on the right side when it is at the off current condition.
The second picture describes the change of exponential current when adding the reverse voltage bias to the terminals of organic Schottky barrier diode. It was supposed to be a smooth curve in ideal condition, however the data given by the supervisor shows that this organic Schottky barrier diode is not perfect. It is clear that the value of exponential current increasing slowly when the value of reverse voltages bias is between -1 to 0. This may because the interface of the material is not perfect to stop the electrons cross it quickly.
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 Finally, we should calculate the value of To according to the equation:

Figure 2: The relationship between current and reverse voltage bias

  The plot shown in the picture 3 was quite successful. According to the given data and the picture, it can be seen that the diode is not ideal. There is a part of folding line instead of the smooth exponential line. On the whole, the plot is quite similar to the ideal graph shown by the supervisor.

 Figure 3. The relationship between current density and voltage

  As a result, different students got different answers. However, because of choosing the inappropriate variables, all of the students calculate the wrong value of To , about 10 times of the right range of answer. Then it was calculated again, there is a table shown the correct results of the To. Different region got the different value of To.

Table 1: The values of To