What is the structure of a typical photovoltaic cell? The structure of photovoltaic cells, taking monocrystalline silicon photovoltaic cells as an example, is mainly composed of a layer of N-type silicon and a layer of P-type silicon. A PN junction is formed at the interface of the two layers of silicon, and the outer sides of the two layers of silicon can conduct electricity. electrode.
When sunlight hits the silicon wafers of photovoltaic cells, new electron-hole pairs are formed, resulting in a dramatic increase in the number of charge carriers in the silicon wafers. The positively charged holes in the N-type semiconductor move to the P-type region, while the negatively charged electrons in the P-type region move to the N-type region. In this way, the positively charged holes on the P-type side of the PN junction become more and more The more; there are more and more negatively charged electrons on one side of the N-type region of the PN junction, thus forming a potential difference on both sides of the PN junction. If the photovoltaic cell and the electric light are connected with wires in the way shown in Figure 1, under the sunlight, the photovoltaic cell will emit electricity and the electric light will be lit.
From the above examples, it can be found that the mystery of photovoltaic cells lies in this “PN junction”. The PN junction is like a wall that hinders the movement of electrons and holes. When the photovoltaic cell is irradiated by sunlight, the electrons receive light energy and move to the N-type region, making the N-type region negatively charged, while the holes move to the P-type region, making the P-type region positively charged. In this way, a potential difference is generated across the PN junction, which is commonly referred to as a voltage.