411 pn Junction

As explained earlier, an n-type material has some impurity atoms with more electrons than the rest of the semiconductor atoms. If those excess electrons are removed, the impurity atoms will fit more uniformly in the structure formed by the main semiconductor atoms; however, the atoms will be left with positive charges. On the other hand, a p-type material has some impurity atoms with fewer electrons than the rest of the semiconductor atoms. Therefore, these atoms seem to have holes that could accommodate excess electrons, even though the atoms are electrically neutral. If additional electrons could be brought to fill the holes, the impurity atoms would fit more uniformly in the structure formed by the main semiconductor atoms, however, the atoms would be negatively charged.

The above scenario occurs at the junction when p- and n-type materials are joined together, as shown in Figure 4.5. As soon as the two materials are joined, excess electrons from the n layer jump to fill the holes in the p layer. Therefore, close to the junction, the material has positive charges on the n side and negative charges on the p side. The p-n junction behaves like a diode. This diode character of a p-n junction is utilized in PV cells as explained below.

FIGURE 4.5

Schematic diagram of p-n junction in silicon.

Solar Stirling Engine Basics Explained

Solar Stirling Engine Basics Explained

The solar Stirling engine is progressively becoming a viable alternative to solar panels for its higher efficiency. Stirling engines might be the best way to harvest the power provided by the sun. This is an easy-to-understand explanation of how Stirling engines work, the different types, and why they are more efficient than steam engines.

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