What are Intrinsic Semiconductors and Impurity Semiconductors - Why are semiconductor materials necessary for photovoltaic cell fabrication?

Photovoltaic Cells – What are Intrinsic and Impurity Semiconductors? How are they different?

Photovoltaic cells are made of semiconductors. Therefore, semiconductors are the main body of photovoltaic cells. It can be said that there is no photovoltaic cell without semiconductors. Semiconductors are the soul of photovoltaic cells. Therefore, if you want to understand photovoltaic cells, you should first understand semiconductors, what is semiconductors, and what are the characteristics of semiconductors. Mastering these basic knowledge is extremely beneficial to understanding the manufacture of photovoltaic cells. If you are also interested in other battery knowledge, you can visit tycorun.com.

  1. Why are photovoltaic cells made of semiconductor materials?
Using semiconductor photovoltaic effect to convert light energy into electricity
Using semiconductor photovoltaic effect to convert light energy into electricity

Because photovoltaic cells are devices that directly convert solar energy into electrical energy, that is, rely on the photovoltaic effect of materials to generate electricity, therefore, the main material for the production of photovoltaic cells must have photovoltaic effect characteristics. When solar energy is converted into electricity, photovoltaic cells cannot be produced. Semiconductor materials are materials with photovoltaic effect properties, so they can be used to make photovoltaic cells.

In fact, not all semiconductor materials can be used to make photovoltaic cells. There are many kinds of semiconductor materials, but some semiconductor materials are not suitable for manufacturing photovoltaic cells due to high price, difficult processing, pollution, resource shortage, and weak photovoltaic effect characteristics.

The semiconductors that can really be used as photovoltaic cell materials include monocrystalline silicon, polycrystalline silicon, amorphous silicon, GaAs, GaAlAs, InP, CdS, CdTe, etc. Among them, single crystal silicon, GaAs, InP are used for space; single crystal silicon, polysilicon, and amorphous silicon are used for mass production on the ground. Others are still in development. At present, the photovoltaic industry is working on reducing material costs and improving conversion efficiency, so that the electricity price of solar cells can be competitive with that of thermal power generation, thereby creating favorable conditions for wider and larger-scale applications.

  1. What is an intrinsic semiconductor? What is an impurity semiconductor?
Intrinsic semiconductor structure characteristics
Intrinsic semiconductor structure characteristics

There are semiconductors in our daily mobile phones, computers, TVs, air conditioners, and cars. Therefore, it seems that everyone knows what semiconductors are now, but if you ask what intrinsic semiconductors are, not many people know about them. .

What is an intrinsic semiconductor?
Intrinsic means having original characteristics. The so-called intrinsic semiconductor refers to a single crystal semiconductor that is completely pure, does not contain any impurities, and has a very complete structure and no lattice defects. Since the English of intrinsic semiconductor is intrinsic semiconductor or proper semiconductor, intrinsic semiconductor is also called I-type semiconductor.

In fact, semiconductors cannot be absolutely pure, and intrinsic semiconductors are generally pure semiconductors whose electrical conductivity is mainly determined by the intrinsic excitation of the material. Both silicon and thread are tetravalent elements with four valence electrons in the outermost shell of their nucleus. They are all “single crystals” composed of the same atoms and belong to intrinsic semiconductors.

Impurity semiconductors, as the name suggests, are semiconductors that contain a certain amount of impurities. However, it should be noted that impurity semiconductors do not refer to ordinary semiconductors containing a certain trace amount of impurities, but to those intrinsic semiconductors artificially doped with trace impurities in proportion. According to the different doped elements, impurity semiconductors can be divided into two types: one is N-type semiconductor; the other is P-type semiconductor.
In semiconductors, both electrons and holes are carriers, and the type of carriers with a larger number is called the majority carrier, and on the contrary, the type of carriers with a smaller number is called the minority carrier.

N is the abbreviation of English negative, which means negative. An N-type semiconductor is a semiconductor in which the number of negatively charged free electrons is much greater than the number of positively charged holes. That is, in an N-type semiconductor, the negatively charged free electrons are the majority carriers.

P is the abbreviation of positive in English, which means positive. A P-type semiconductor is a semiconductor in which the number of positively charged holes is much greater than the number of negatively charged free electrons. That is, in a P-type semiconductor, the positively charged holes are the majority carriers.

The difference between intrinsic semiconductors and impurity semiconductors is that the number of free electrons and holes in intrinsic semiconductors are equal, and they have extremely high resistance at room temperature, but only show lower resistance at high temperatures; The number of free electrons and holes in the impurity semiconductor is not equal, and it has a lower resistance at room temperature. After adding a voltage, the semiconductor will have a current flow. The size of the impurity semiconductor resistance is related to the type of impurity and the concentration of the impurity.
Read more: Why do photovoltaic cells have to use polysilicon with a purity higher than 6N?

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