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Met eigen ogen download Photoelectric Properties and Applications features with one or more techniques of the Commission. Except above transition metal dopants, other transition metal atoms, including tungsten W [ — ], silver Ag [ — ], copper Cu [ , ], cobalt Co [ — ], tantalum Ta [ — ], molybdenum Mo [ — ], zinc Zn [ — ], manganese Mn [ , ], nickel Ni [ , ], and vanadium V [ , ], are also investigated by many researchers.
Ag is another important dopant in TiO 2 crystals and Ag doping can also cause an obvious shift towards narrowing the bandgap. They found that Ag doping played a great role in the photocatalytic activity. Electron transfer to the Ag sites reduced the carrier recombination rate and allowed a more effective reaction between the surface trapped holes and electrons. However, excessive Ag dopant could also cause a decrease in the activity of TiO 2 because they occupied the active sites on the surface of the TiO 2.
Moreover, the photogenerated electrons on the Ag sites attracted holes and recombined together. Cu, as a kind of transition metal, is also found to be an effective dopant for TiO 2 to enhance the photocatalytic activity. Cai et al. Sengele et al. Recently, many researchers found that transition metal could effectively modulate the crystal face, which could improve photocatalytic performance [ — ]. Saad et al. This approach appears to be a completely new alternative for enhancing the efficiency of the photocatalytic process. Therein, lanthanide La has been widely used and investigated in the field of optical application LED light, laser, photocatalytic, solar cell, etc.
Du et al. The results showed that the content of La was the key factor for hydrophilic and photocatalytic activity. By adding 0. Maddila et al.
Photocatalyzed ozonation with 1at. Among various upconverting nanomaterials, erbium Er can be excited by NIR or visible light [ — ]. Choi et al.
Europium Eu is also a good candidate for upconversion materials and is widely used in the field of photocatalyst, laser, solar cell, etc. Recently, many researchers also attempted to dope Eu into TiO 2 lattice [ — ]. Leroy et al. Correlation of the emission with the photocatalytic activity of the semiconductor for the photodegradation of an organic molecule could also be firmed.
Yttrium Y doping usually shows weak influence on bandgap energy and does not alter the Fermi level. Wu et al. The 2. Recently, many researchers found that lithium Li doping plays an important role in the inhibition of activity in the TiO 2 network acting as an electron trapping or hole trapping [ — ].
Bouattour et al. Results showed that an inhibition of activity is presented in the Li doping network. Long et al. The reduction of the bandgap is 0. However, there were enlargements of 0. Doping with bismuth Bi ions can also decrease the bandgap of TiO 2 and thereby extend its absorption into the visible light region, enhancing its photocatalytic efficiency [ — ].
The impurity energy level from the hybrid of Bi 6s, O 2 p , and Ti 3 d orbitals is the cause of the red shift of the absorption edge. Bi doping caused the formation of Bi x TiO y and reduced bandgap widths. Sn doping is another important supplementary form to improve photocatalytic performance [ , ].
This volume discusses the photoelectric behavior of three semiconducting thin film Photoelectric Properties and Applications of Low-Mobility Semiconductors. Download Citation on ResearchGate | Photoelectric Properties and Applications of Low-Mobility Semiconductors | The book deals with the physics behind the.
Oropeza et al. This was attributed to the narrowing of the bulk bandgap at low doping levels. The Sn surface states laid above the VB top and could therefore act as trapping sites for holes. Although the monodoped nonmetal or metal atoms can obviously enhance photocatalytic performance, they always act as the recombination centers because of the partially occupied impurity bands.
It has been recognized theoretically that codoping using two or more foreign atoms can passivate the impurity bands and decrease the formation of recombination centers by increasing the solubility limit of dopants. Furthermore, codoping can also modulate the charge equilibrium. Consequently, codoping can effectively enhance the photocatalytic activity.
Based on the research of doping effects, two or more elements are introduced into TiO 2 lattice to check the changes of electronic structure and bandgap energy, including nonmetal and nonmetal atoms [ — ], nonmetal and metal atoms [ — ], and metal and metal atoms [ — ]. Therefore, it is a challenge and hot topic to introduce different dopants, which can realize substantial synergistic effects. Consequently, the VB of TiO 2 shifts to a positive direction, which leads to higher oxidative ability and degradation ability towards pollutant under visible light irradiation.
Etacheri et al. Chung et al. They found that the N, S codoped TiO 2 had better visible light photocatalytic activity and adsorptivity than the commercially available P The S dopants effectively assisted the surface reaction by adsorbing cations of organic dyes on the codoped TiO 2 surface. Schematic illustration of the suggested effects of N and S dopants on the enhanced visible light photocatalytic activity of TiO2 [].
It is noteworthy that N, S codoping can also effectively modulate the preferential growth plane of TiO 2 crystals.
Xiang et al. These resulted in stronger absorption with a red shift in the bandgap transition. Recently, Samsudin et al. Subsequently, a great number of experiments and theoretical calculations were carried out to further discuss N, F codoping in TiO 2 crystals [ — ]. Further investigation showed that the enhancement of photocatalytic activity could be attributed to the bandgap scattering effect and the slow photon effect, leading to a significant improvement in solar light harvesting.
N, B codoped TiO 2 is also an effective approach to improve photocatalytic activity [ — ]. Usually, N and B atoms are interstitial species connected to the same O lattice.
Moreover, the presence of N and B species can effectively narrow the bandgap and inhibit the transformation of anatase TiO 2 to rutile phase [ ]. Recently, Wei et al.
The substitutional nonmetal doping of N and H, especially the p states of N, contributed to the bandgap narrowing by mixing with O 2 p states and formed the new VB. The bandgap energy of the samples also decreased substantially, which was narrowed to about 2. Yu et al. The further calculation indicated that B 2 p and C 2 p decreased the bandgap by about 0. Deng et al. The C atoms and F species interacted in the TiO 2 lattice and resulted in the narrowed bandgap 2.
They found that both B and P dopants could also narrow the bandgap of the TiO 2 catalyst. Recently, many researchers found that tridoping in TiO 2 crystals is an effectively supplemental tool. Ramanathan and Bansal synthesized N, C, F tridoped rutile TiO 2 nanorods that not only displayed enhanced photocatalytic performance in UV light but also allowed a significant level of visible light photocatalytic activity [ ]. Although monometal doping can improve the bandgap structure, the serious recombination centers also deteriorate carrier transport due to its partially occupied impurity bands.
Hence, many researchers want to improve carrier transport through codoping with two different metal elements, such as Ti, Ni codoping [ ], Ti, Fe codoping [ ], Ag, W codoping [ ], Ag, Zr codoping [ ], Zn, Mn codoping [ ], Cu, V codoping [ ], and Fe, Ce codoping [ ]. In other words, Ti, Ni codoped porous black anatase TiO 2 resulted higher photocatalytic performance for methyl orange and rhodamine B. Chen et al. The codoped TiO 2 displayed pure anatase phase with strong absorption in visible light region.
Among all the codoped samples, the one with W doping concentration of 3. Benjwal and Kar investigated Zn, Mn codoped TiO 2 photocatalysts through varying dopant concentrations and found that the highest photocatalytic degradation of methyl blue was obtained with 1.
Silicon is a fourfold coordinated atom that is normally tetrahedrally bonded to four neighboring silicon atoms. Ran Kim, Paul S. Dongge Ma Corresponding Author E-mail address: msdgma scut. For most measurement conditions the initial state is thermalized, such that only a few vibrational states are excited. And he sets no Page what aims Addressed. Whereas the processing is performed mostly in purely electronic devices based on mono-crystalline Si, information transfer uses electro-optical processes in III—V and II—VI compound semiconductors. So far, however, these techniques have remained restricted to wafer-size dimensions.
With further increasing codoping concentration, the density of new energy levels also increased, which ultimately enhanced the recombination possibilities of electron and holes because they could be easily trapped on these recombination centers.