光敏元件

光敏元件，又称光敏电阻或光敏电阻器（LDR），是一种被动半导体器件，其电阻随入射光强度的增加而减小。它基于光电导原理工作，即具有足够能量的光子将电子从价带激发到导带，增加载流子数量，从而降低电阻。在工业光电传感器中，它作为主要传感元件，用于检测自动化系统中的存在、位置或光照水平。

工作原理基于光电导效应。当光子照射到半导体材料（通常是硫化镉或硒化镉）上时，它们提供足够的能量将电子从价带激发到导带，产生电子-空穴对。这增加了自由载流子的数量，从而按比例降低材料的电阻。在黑暗中，电阻很高（通常为兆欧级），而在光照下，电阻显著下降（至千欧或更低）。通过电路测量这种电阻变化，产生输出信号。

The working principle is based on photoconductivity. When photons strike the semiconductor material (typically cadmium sulfide or cadmium selenide), they provide enough energy to excite electrons from the valence band to the conduction band, creating electron-hole pairs. This increases the number of free charge carriers, which lowers the electrical resistance of the material proportionally to the light intensity. In darkness, the resistance is high (typically megaohms), while under illumination, it drops significantly (to kiloohms or less). This resistance change is measured by a circuit to produce an output signal.