“n-type” vs. “p-type” semiconductor structure in solar cells

The conductivity of semiconductors (Silicon & Germanium) can be adjusted by putting a small number of impurities into their crystal structures. This impurity leads to better conductivity among semiconductors. Impurities based on the number of valence electrons could be n-type (5) or p-type (3). 

The n-type tends is a better choice due to reducing LID (Light Induced Degradation) & increase durability and performance compared to p-type.

n-type: Silicon with 5 valence electrons impurities produces n-type semiconductors in which one extra electron contributes to increase the electrical conductivity of the semiconductor. 

p-type: However, in p-type semiconductor or 3 valence electrons impurities doped in silicon, remained one hole, deficiency of electrons in the valence band of the semiconductor.

Examples of elements with 5 valence electrons in the valence band are antimony, arsenic or phosphorus and with 3 valence electrons are boron, aluminum or gallium.

What are semiconductors? Semiconductors are a type of elements that have special properties such as electrical conductivity and falling resistance when exposed to rising temperatures. As a result of these properties, they placed between two main kinds of elements, conductors and insulators. Conductors have great electrical conductivity, copper for instance, and their resistance increases when their temperatures rise. Contrary to conductors, insulators, such as glass, have low resistance when their temperatures go up but they are not good at electrical conductivity.



Photo:@hyperphysics & @Solar_Edition


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