7.3 Characteristics of photoresistor
Before doing the experiment, we should understand the properties and principle of photoresistor. So, in the section, we will focus on the introduction to the characteristics of photoresistor.
It is also called as photoelectronic effect, or photosensitive effect, and introduced by the Semiconductor materials conductivity change. That is, when the material absorbs the photon energy, which can generate the intrinsic absorption or impurity absorption. This would cause the change of the carrier concentration, and thus make the material conductivity change. This phenomenon is called the photoelectronic effect.
express of photo resistor
The photoresistor is a resistor, whose value would be changed by the change of the strength of the incident light by use of the photoelectronic effect. Thus, it is also named as the photoconductive detector. More stronger of the incident light, the resistor value decreases; while weaker, the value of resistor increases. In addition, there exists another contrary change resistor, as shown in Figure 7-1. Generally speaking, its letter label can be written as “RL”, “RG”, or “R”.
photoresistor (b) express of photoresistor
Figure 7-1 photoresistor and its express
Some materials have the photoconductive effect, such as Si, Ge, CdS, CdSe, PbS, and so on. The products generated from these materials can change the electrical conductivity along with the strength of the incident light.