Views: 0 Author: Site Editor Publish Time: 07-12-2021 Origin: Site
The excited state of the photoluminescent tape is an important substance that enables it to emit light, but I think most people should not know what is the excited state of the photoluminescent tape. The distribution of excited states in the photoluminescent tape can be divided into three regions based on energy levels. Do you know how they are divided?
Here is the list of contents.
What are the excited states in the photoluminescent tape below the forbidden bandwidth?
What is the excited state of the photoluminescent tape near the forbidden bandwidth?
What are the excited states of electrons in the conduction band?
The excited states in the photoluminescent tape below the forbidden band are mainly the excited states at the discrete centers. The study of the energy spectrum terms of these excited states and their properties involves the interaction between the impurity center and the dot matrix, which can be analyzed using crystal field theory. As this interaction strengthens, both absorption and emission spectral bands become narrower and wider, temperature effects become weaker and stronger, and especially the bursting phenomenon becomes stronger, turning part of the excitation energy into dotted-field vibrations. In the case of stronger interaction, the excited or ground state of the photoluminescent tape can only represent the central and dotted states, which is a unified system. It is usually represented by a bit-shaped coordinate curve. The electron hopping generally occurs near the very small value of the curve. However, recent studies of superheated luminescence have shown that luminescence can also start at relatively high vibrational energy levels, which can be visualized in the time-division spectrum, reflecting the structure of the phonons involved in the jump.
The photoluminescent tape excited states close to the forbidden bandwidth are relatively abundant and include free excitons, bound excitons, and host-host pairs. Exciton molecules also appear when the excitation density is high, and electron-hole droplets can be observed even in indirect band-gap semiconductors. Excitons can be coupled to photons of similar energy to form electromagnetic excitons (exciton-polaritons). The luminescence of bound excitons is a common phenomenon, and small differences in their binding energies are often used to reflect the properties of the binding center. In inorganic molecular crystals, the electronically excited state of the lowest photoluminescent tape is the triplet exciton state, while the single-state exciton has almost twice the energy of the triplet exciton. Due to the presence of similar molecules in the vicinity, two effects occur in molecular crystals." Red-shift" (about a few hundred centimeters) and "Davydov cleavage". These two effects have a greater impact on the single state than on the triplet state.
The high-energy excited states of the photoluminescent tape are the states in which the electrons in the conduction band are located, including the hot carriers. The latter are excited by light at higher energies. The carriers are excited to a thermal equilibrium state above the conduction band (or valence band), and their distribution is usually described by the electron (or hole) temperature (as opposed to the spot temperature). Experiments show that hot carriers do not need to fully exchange energy with the dot matrix until they reach thermal equilibrium with the dot matrix to compound luminescence, although their compound cross-section is smaller than the latter. Hot carriers can also leap to lower energies within the conduction band (or valence band). This type of luminescence can reflect the band structure and associated properties.
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