LASER diode and pin diode

Photo transistor and DIAC

Photo diode and transistor

Photo resistor and TRIAC

Considerably lower sensitivity

Limit voltage handling capacity

Considerable greater sensitivity

Vulnerable to electrical sources

Used in comparator circuit

Used as light controlled switch

Used as oscillator

Used as demodulator

More sensitive

Available different sizes and specifications

Cannot be used to determine precise light levels

Made of low resistance material with few holes

Silicon

Germanium

Aluminium

Cadmium sulfide