Studies reveal the dynamic mechanism of ultra-fast exciton removal kinetics of two-dimensional calcium titanium ore
Affected by light, the semiconductor produces carrier electronics and holes, the two are bundled with opposite charges to be bundled with electrostatic attraction, forming an excitor. Compared to free electrons and holes, the excitons have higher luminous efficiency thus having potential value in the field of illumination and display devices; however, in photovoltaic applications such as solar cells, a large amount of excitons are not conducive to positive and negative charge. Separate extraction so that the solar cell efficiency is significantly reduced.
Therefore, it is important to guide the dynamic process of mutual transformation between the exciton and the free carrier in the semiconductor, which has important guiding significance for the rational application of materials and devices.
Recently, Jin Sheng, a research institute of Dalian Chemical Physics, Chinese Academy of Sciences, has made a new progress in the study of (quasi) two-dimensional calcium titanium ore excitement. The team first observed the fast dynamic exciton dissociation process in the two-dimensional calcium titanium mine through ultra-fast time resolution spectroscopy techniques, and thus proposed to demonstrate the new mechanism of exciton reduction induced by polarized sub-shielding effects. The relevant research results were published in "American Chemical Members".
As a type of natural quantum well material, high-quality semiconductor media, two-dimensional calcium-titanium-state exciton can increase significantly compared to traditional three-dimensional calcium titanium ore, reaching hundreds of millivotic fluvine, so that excitons are difficult to at room temperature Dissociation.
Previously, traditional views believe that the photovoltaic carriers in the two-dimensional calcium-titanium mine mainly exist in the form of excitons, and it is difficult to dissociate to form a free carrier at room temperature to speculate that two-dimensional calcium titanium mine is not suitable for photovoltaic devices such as solar cells. . However, some recent studies have found the results of the opposite. The research team speculates that the previous research may, because ignore the interaction between the photosensome and the lattice, thereby overestimating the exciton binding energy of the two-dimensional calcium titanium ore.
In order to verify, the team passed the femtosecond super fast spectroscopy technology, etc. The state is mainly present in the form of a free carrier. This has a large difference in higher excites that have been previously reported by steady-state absorption spectroscopy. In order to explain this abnormal physical phenomenon, the team further passes low temperature spectroscopy, etc., proposes the exciton cleavage mechanism induced by excitement polarization, that is, the exciton is formed by strong coupling between the phoracic. Sub-polarized, due to the masking of polarizes, the excited state binding can significantly decrease significantly, thereby promoting the rapid dissociation of excitons. In addition, it is also proved that exciton dissociation and subsequent free carrier non-radiation composite process are the main factors that limit the fluorescence quantum efficiency of two-dimensional calcium titanium ore.
This finding revealed that polarized exciton removal characteristics in two-dimensional calcium titanium mine materials, providing theoretical guidance for applications in photovoltaic and photodetects such as photovoltaic and photovoltaic probe.