As a low-cost, high-efficiency solar cell material, perovskite based on lead has been widely concerned. However, the inherent instability and toxicity of lead (Pb) has caused serious concern about the feasibility of lead-based perovskites as solar cell materials, which has hindered the large-scale commercialization of solar cells and similar devices based on these materials. Although lead-free perovskite can be used as an alternative to compensate for the toxicity of lead-based perovskite, it is not very useful due to its low efficiency.
A recent study led by Tae-Hyuk Kwon, a professor at the Natural Science Institute of Ulsan University of Science and Technology (UNIST) in South Korea, took an important step in the development of a new generation of solar cells. This study used lead-free perovskite. This new perovskite material has good electrical properties and can be used as a charge regenerator for dye-sensitized solar cells, thereby improving the overall efficiency and stability of the battery.
The research results were published in the November 2018 issue of Advanced Materials, and this discovery will open up new possibilities for the application of lead-free perovskites in solar cells.
In various alternatives to lead, the research team used blank sequence double perovskite (Cs2SnI6). Despite the promising outlook, the surface state and function of Cs2SnI6 are still unclear. Therefore, it is necessary to conduct a comprehensive study of these characteristics of Cs2SnI6, in order to provide a reference for the design of Cs2SnI6-based devices in the future.
To clarify the function of the surface state of Cs2SnI6, the team studied the charge transfer mechanism and developed a three-electrode system to observe the charge transfer in the surface state of Cs2SnI6. In addition, cyclic voltammetry and Mott-Schottky (Mott-Schottky) analysis were also used to detect the surface state of Cs2SnI6 and found that the electric potential was related to its band gap.
The analysis shows that the surface state of Cs2SnI6 has a high redox activity and can be effectively charged / discharged in the presence of iodine redox medium. In addition, the preparation of a charge regeneration system based on Cs2SnI6 confirmed that charge transfer occurs through the surface state of Cs2SnI6.
Researcher HyeonOh Shin of Ulsan University of Science and Technology in South Korea pointed out that the study found that charge transfer occurs through the surface state of Cs2SnI6, which will help design future electronic and energy equipment using lead-free perovskite materials.
Based on this strategy, the research team designed a hybrid solar cell using a charge regenerator based on Cs2SnI6 for organic dye-sensitized solar cells (DSSCs). This type of solar cell generates current during the process of oxidizing the organic dye to its original state.
Byung-Man Kim, the other main founder of the study, also pointed out that due to the high charge in the organic dyes and the high surface state of Cs2SnI6, it generates more current. Therefore, Cs2SnI6 has a good thermodynamic charge acceptance level, and its photocurrent density is increased by 79% compared with the traditional liquid electrolyte.
In this study, the Cs2SnI6 charge transfer mechanism was studied to clarify the function of its surface state, which attracted wide attention in the research session. The results of this study indicate that in the presence of redox mediators, the surface state of Cs2SnI6 is the main charge transfer route, which should be considered in future Cs2SnI6-based device design.
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