All the Rechargeable work light, portable camping light and multifunctional headlamp use the LED bulb type. To understand the principle of diode led, first to understand the basic knowledge of semiconductors. The conductive properties of semiconductor materials are between conductors and insulators. Its unique features are: when the semiconductor is stimulated by external light and heat conditions, its conductive ability will change significantly; Adding small amounts of impurities to a pure semiconductor significantly increases its ability to conduct electricity. Silicon (Si) and germanium (Ge) are the most commonly used semiconductors in modern electronics, and their outer electrons are four. When silicon or germanium atoms form a crystal, neighboring atoms interact with each other, so that the outer electrons become shared by the two atoms, which forms the covalent bond structure in the crystal, which is a molecular structure with little constraint ability. At room temperature (300K), thermal excitation will make some outer electrons get enough energy to break away from the covalent bond and become free electrons, this process is called intrinsic excitation. After the electron is unbound to become a free electron, a vacancy is left in the covalent bond. This vacancy is called a hole. The appearance of a hole is an important feature that distinguishes a semiconductor from a conductor.
When a small amount of pentavalent impurity such as phosphorus is added to the intrinsic semiconductor, it will have an extra electron after forming a covalent bond with other semiconductor atoms. This extra electron only needs very small energy to get rid of the bond and become a free electron. This kind of impurity semiconductor is called electronic semiconductor (N-type semiconductor). However, adding a small amount of trivalent elemental impurities (such as boron, etc.) to the intrinsic semiconductor, because it has only three electrons in the outer layer, after forming a covalent bond with the surrounding semiconductor atoms, it will create a vacancy in the crystal. This kind of impurity semiconductor is called hole semiconductor (P-type semiconductor). When N-type and P-type semiconductors are combined, there is a difference in the concentration of free electrons and holes at their junction. Both electrons and holes are diffused towards the lower concentration, leaving behind charged but immobile ions that destroy the original electrical neutrality of the N-type and P-type regions. These immobile charged particles are often called space charges, and they are concentrated near the interface of the N and P regions to form a very thin region of space charge, which is known as the PN junction.
When a forward bias voltage is applied to both ends of the PN junction (positive voltage to one side of the P-type), the holes and free electrons move around each other, creating an internal electric field. The newly injected holes then recombine with the free electrons, sometimes releasing excess energy in the form of photons, which is the light we see emitted by leds. Such a spectrum is relatively narrow, and since each material has a different band gap, the wavelengths of photons emitted are different, so the colors of leds are determined by the basic materials used.
Post time: May-12-2023