How solar cells work, some unique designs of solar cells

How Solar Cells Work

    Solar cells are semiconductor devices that efficiently absorb solar radiation and convert it into electrical energy. They are also called photovoltaic cells because they utilize the photovoltaic effect of various potential barriers. At the heart of these devices are electron-releasable semiconductors.

    The most commonly used semiconductor material is silicon. Since silicon is abundant in the earth's crust, it can be said to be inexhaustible. When sunlight shines on the surface of the semiconductor, the valence electrons of the atoms in the N and P regions of the semiconductor are excited by solar photons and obtain energy beyond the forbidden bandwidth through light irradiation. Therefore, the conduction band generates many electron-hole pairs in an unbalanced state in the semiconductor material. These photoexcited electrons and holes collide freely or recombine to a balanced state in the semiconductor.

    The recombination process does not show an external conductive effect. It is part of the automatic loss of energy in solar cells. The minority carriers in the photoexcited carriers can move to the PN junction area and drift to the opposite area through the PN junction minority carrier pull effect, forming a PN junction barrier photoelectric field in the opposite direction.

    After connecting to an external circuit, power output can be obtained. When a large number of such small solar photovoltaic cells are combined in series and parallel to form a photovoltaic cell module, a sufficiently large amount of power can be output under the action of solar energy. The semiconductor material used for solar cells must have a suitable bandgap width.

    Semiconductors with different band gaps absorb only part of the solar radiation energy to generate electron-hole pairs. The smaller the band gap width, the larger the part of the solar spectrum that can be absorbed. At the same time, the energy wasted near the peak of the solar spectrum will be greater. It can be seen that only by selecting semiconductor materials with suitable band gap width can the solar spectrum be used more efficiently. Since direct transfer semiconductors have higher light absorption efficiency than indirect transfer types, they should be direct transfer semiconductors.

Some unique designs of solar cells

    1. Electronic energy-saving batteries

    The energy-saving battery strikes a perfect balance between solar cell area (power generation efficiency) and portability. The product doesn't look much different from the usual portable power bank. It still has a cylindrical shape and outputs through a USB port - but it has a flexible solar cell built in, and when needed, hold the back of the pole and pull out the solar cell like a scroll to get the maximum light area, thereby improving power generation efficiency. In peacetime, you can also put the panel away, which is convenient and not occupied.

    2. Foldable solar cells

    In energy-saving batteries, we mentioned a flexible solar cell that can be rolled up. So, can solar cells be rolled up? As early as 2009, an American named Frederik Krebs created a solar film that can be rolled up or straightened, which even has ultra-thin lithium batteries and LEDs attached to it. During the day, you can straighten it and stick it to the wall, and it will be able to convert solar energy into electricity and store it. At night, you can put it in the house as room lighting. If necessary, you can also roll it into a tube like a flashlight. According to Krebs's vision, in the final mass production of this solar LED film, the cost of each piece will be less than $7.

    3. Sun Cat

    SunCats are a design by Knut Karlsen. In fact, it is more like a solar sticker than a solar cell, equivalent to a solar cell attached to the surface of a normal rechargeable battery. So when it is out of power, just throw it on the windowsill and let it catch some sunlight.

    4. Sunlight

    sunLight was designed by German designer Hermann Eske. The main body of sunLight is a solar panel that can be rolled together. In addition to directly charging electronic devices like most solar devices, it also has other special features. If you have a close-up view, you will find that it looks a little different. There are six hollow small cylinders on the back. All the mystery lies inside these cylinders, any of which can be considered a small LED flashlight powered by two AAAA rechargeable batteries built in and rolled up as a powerful flashlight with six LEDs.