Solar energy is an inexhaustible renewable energy source for human beings. It is also clean energy and does not cause any environmental pollution. Among the effective utilization of solar energy, solar photovoltaic utilization is the fastest developing and most dynamic research field in recent years, and it is one of the most eye-catching projects.
Solar energy is a form of radiant energy that can only be converted into electricity by means of an energy converter. This energy converter, which converts solar energy (or other light energy) into electricity, is called a solar power battery.
The basic working principle of solar power batterys
The working principle of solar power batterys is based on the "photoluminescence" effect of semiconductor p-n junction. The so-called photovoltaic effect is simply an effect of electromotive force and current caused by the change of charge distribution in the body of an object when it is exposed to light.
When the sun or other light irradiates the PN junction of the semiconductor, electron-hole pairs are generated. The carriers generated near the P-N junction inside the semiconductor are not recombined and reach the space charge region. Attracted by the internal electric field, electrons flow into the N region and holes flow into the P region, resulting in the storage of excess electrons in the n region and excess holes in the p region. They form a photogenerated electric field near the p-n junction in the direction opposite to the barrier.
In addition to partially canceling the barrier electric field, the photogenerated electric field also makes the p region positively charged and the n region negatively charged. The thin layer between the n region and the p region generates electromotive force, which is the photogenerated volt effect. When energy is added to pure silicon (in the form of heat, for example), it causes several electrons to break away from their covalent bonds and leave the atom.
Every time an electron leaves, it leaves a hole. The electrons then wander around the lattice, looking for another hole to take up residence in. These electrons are called free carriers, and they can carry current.
This electric field is equivalent to a diode, allowing (and even pushing) electrons to flow from the p side to the n side, rather than the other way around. When light hits a solar power battery in the form of photons, its energy releases pairs of electron holes. Each photon carrying enough energy usually releases exactly one electron, creating a free hole.
If this happens close enough to the electric field, or if the free electron and the free hole are just within its sphere of influence, the electric field will send the electron to the N side and the hole to the P side. This leads to further destruction of the electrical neutrality, and if we provide an external current path, the electrons will pass through that path to their original side (the p-side), where they will merge with the hole sent by the electric field and do work as they flow. This creates an electric current from the N-type region to the P-type region. A potential difference is then formed in the PN junction, which forms the power supply.
Since the semiconductor is not a good conductor of electricity, if the electrons flow in the semiconductor after passing through the p-n junction, the resistance is very large, and the loss is very large. However, if the upper layer is fully coated with metal, the sunlight cannot pass through and the current cannot be generated, so the p-n junction is generally covered with a metal mesh (as shown in the comb electrode) to increase the area of incident light.
In addition, the silicon surface is so bright that it reflects a lot of sunlight and cannot be used by batteries. To do this, the scientists coated it with a protective coating with a very small reflection coefficient, reducing the reflection loss to 5 percent or less. After all, a battery can only provide a limited amount of current and voltage, so many batteries are connected in parallel or in series to form solar photovoltaic panels.
solar power batterys produce electricity according to the photoelectric properties of specific materials. Black bodies (like the sun) emit electromagnetic waves of different wavelengths (corresponding to different frequencies), such as infrared, ultraviolet, visible light, and so on. When these rays hit a different conductor or semiconductor, the photons interact with the free electrons in the conductor or semiconductor to generate an electric current.
The shorter the wavelength and the higher the frequency, the higher the energy. For example, the energy of ultraviolet ray is much higher than that of infrared ray. However, not all wavelengths of ray energy can be converted into electricity, it is worth noting that the photoelectric effect is independent of the intensity of the ray, only when the frequency reaches or exceeds the threshold of photoelectric effect, the current can be generated.
solar power battery power generation is a renewable and environmentally friendly way of power generation, which will not produce greenhouse gases such as carbon dioxide and pollute the environment.