Abstract
Element doping is commonly used to adjust the carrier concentrations in semiconductors such as thermoelectric materials. However, the doping process unavoidably brings in defects or distortions in crystal lattices, which further strongly affects the physical properties of the materials. In this work, high energy photons have been used to activate the carriers in Cu2S thermoelectric films. As a result, the carrier concentrations, and the respective electrical conductivity as well as Seebeck coefficient are further changed. The photon-induced electrical transport properties are further analyzed utilizing a Parallel circuit model. Due to the realization of optimized carrier concentrations by photon activation, the power factor of Cu2S film is improved more than 900 times as compared with the dark data. As compared to the traditional doping process, the approach using photon activation can realize the tuning of carrier concentrations without affecting crystal lattice. This method provides an opportunity to investigate the intrinsic physical properties of semiconductor materials without involving traditional element doping process that usually brings in additional lattice defects or distortions.
Highlights
When photons surpass band gap of materials, photo-induced carriers are generated, leading to enhanced carrier concentrations in semiconductors or insulators[11]
The respective changes in Seebeck coefficient and electrical conductivity are defined as photo-Seebeck and photo-conductivity, respectively[9,10]
The phenomenon of photo-Seebeck has been observed in many semiconductor materials, such as Ge12, Si13, GaAs14, ZnO9 and PbO10 for their relatively large band gaps as compared with classic thermoelectric materials[3,15] that usually have narrow band gaps
Summary
This leads to a significant enhancement in the electrical conductivity and reduction in the Seebeck coefficient. Due to the optimization of carrier concentration, the photo-induced power factors are enhanced more than 900 times as compared with the dark data without changing the crystal structures This method provides an additional opportunity to investigate the intrinsic physical properties of thermoelectric semiconductors that excludes the contributions from those unexpected defects or impurities when using other approaches or methods
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