Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userThe Effect of Shallow vs. Deep Level Doping on the Performance of Thermoelectric Materials
292
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
It is well known that the efficiency of a good thermoelectric material should be optimized with respect to doping concentration. However, much less attention has been paid to the optimization of the dopants energy level. Thermoelectric materials doped with shallow levels may experience a dramatic reduction in their figures of merit at high temperatures due to the excitation of minority carriers that reduces the Seebeck coefficient and increases bipolar heat conduction. Doping with deep level impurities can delay the excitation of minority carriers as it requires a higher temperature to ionize all dopants. We find through modeling that, depending on the material type and temperature range of operation, different impurity levels (shallow or deep) will be desired to optimize the efficiency of a thermoelectric material. For different materials, we further clarify where the most preferable position of the impurity level within the band gap falls. Our research provides insights in choosing the most appropriate dopants for a thermoelectric material in order to maximize the device efficiency.
rate research
Read More
Thermoelectric properties of the chemically-doped intermetallic narrow-band semiconductor FeGa3 are reported. The parent compound shows semiconductor-like behavior with a small band gap (Eg = 0.2 eV), a carrier density of ~ 10(18) cm-3 and, a large n-type Seebeck coefficient (S ~ -400 mu V/K) at room temperature. Hall effect measurements indicate that chemical doping significantly increases the carrier density, resulting in a metallic state, while the Seebeck coefficient still remains fairly large (~ -150 mu V/K). The largest power factor (S2/{rho} = 62 mu W/m K2) and corresponding figure of merit (ZT = 0.013) at 390 K were observed for Fe0.99Co0.01(Ga0.997Ge0.003)3.
In this letter, a new approach to chemically dope black phosphorus (BP) is presented, which significantly enhances the device performance of BP field-effect transistors for an initial period of 18 h, before degrading to previously reported levels. By applying 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4-TCNQ), low ON-state resistance of 3.2 ohm.mm and high field-effect mobility of 229 cm2/Vs are achieved with a record high drain current of 532 mA/mm at a moderate channel length of 1.5 {mu}m.
Thermoelectric properties of graphene nanoribbons with periodic edge vacancies and antidot lattice are investigated. The electron-phonon interaction is taken into account in the framework of the Hubbard-Holstein model with the use of the Lang-Firsov unitary transformation scheme. The electron transmission function, the thermopower and the thermoelectric figure of merit are calculated. We have found that the electron-phonon interaction causes a decrease in the peak values of the thermoelectric figure of merit and the shift of the peak positions closer to the center of the bandgap. The effects are more pronounced for the secondary peaks that appear in the structures with periodic antidot.
Whether porosity can effectively improve thermoelectric performance is still an open question. Herein we report that thermoelectric performance can be significantly enhanced by creating porosity in n-type Mg3.225Mn0.025Sb1.5Bi0.49Te0.01, with a ZT of ~0.9 at 323 K and ~1.6 at 723 K, making the average ZT much higher for better performance. The large improvement at room temperature is significant considering that such a ZT value is comparable to the best ZT at this temperature in n-type Bi2Te3. The enhancement was mainly from the improved electrical mobility and multi-scale phonon scattering, particularly from the well-dispersed bismuth nano-precipitates in the porous structure. We further extend this approach to other thermoelectric materials such as half-Heuslers Nb0.56V0.24Ti0.2FeSb and Hf0.25Zr0.75NiSn0.99Sb0.01 and Bi0.5Sb1.5Te3 showing similar improvements, further advancing thermoelectric materials for applications.
We present a study of the electronic properties of Tl5Te3, BiTl9Te6 and SbTl9Te6 compounds by means of density functional theory based calculations. The optimized lattice constants of the compounds are in good agreement with the experimental data. The band gap of BiTl9Te6 and SbTl9Te6 compounds are found to be equal to 0.589 eV and 0.538 eV, respectively and are in agreement with the available experimental data. To compare the thermoelectric properties of the different compounds we calculate their thermopower using Motts law and show, as expected experimentally, that the substituted tellurides have much better thermoelectric properties compared to the pure compound.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
