Time: 2019/1/28 15:01:15 Source: Phoenix Network Technology Author: Views: 2 times

As solar cell materials, lead-based perovskites have received extensive attention. However, the inherent instability and toxicity of lead (Pb) have raised serious concerns about the viability of lead-based perovskites as solar cell materials, hindering the large-scale commercialization of solar cells and similar devices based on these materials.

Although lead-free perovskites can be used as an alternative to compensate for the toxicity of lead-based perovskites, they are less useful due to their lower efficiency.

A recent study led by Professor Tae-Hyuk Kwon of the Faculty of Natural Sciences at Ulsan University of Science and Technology (UNIST) in South Korea has taken a major step forward in developing a new generation of solar cells using lead-free perovskites. This novel perovskite material has excellent electrical properties and can serve as a charge regenerator for dye-sensitized solar cells, thereby improving the overall efficiency and stability of the cells.

The findings, published in the November 2018 issue of Advanced Materials, will open up new possibilities for the use of lead-free perovskites in solar cells.

Among various alternatives to lead, the research team used a blank-order double perovskite (Cs2SnI6). Despite promising prospects, the surface state of Cs2SnI6 and its function remain unclear. Therefore, it is necessary to conduct a comprehensive study on these characteristics of Cs2SnI6 to provide a reference for the design of Cs2SnI6-based devices in the future.

To elucidate the function of the Cs2SnI6 surface state, the group investigated its charge transfer mechanism and developed a three-electrode system to observe the charge transfer under the Cs2SnI6 surface state. In addition, loop voltammetry and Mott-Schottky analysis were also used to probe the surface states of Cs2SnI6 and found that the potential is related to its band gap.

The analysis shows that the surface state of Cs2SnI6 is highly redox active and can be efficiently charged/discharged in the presence of an iodine redox mediator. Furthermore, the preparation of a Cs2SnI6-based charge regeneration system confirmed that the charge transfer occurs through the surface states of Cs2SnI6.

Hyeon Oh Shin, a researcher at Ulsan University of Science and Technology in South Korea, pointed out that the study found that charge transfer occurs through the surface states of Cs2SnI6, which will help design future electronic and energy devices using lead-free perovskite materials.

Based on this strategy, the research team designed hybrid solar cells using a Cs2SnI6-based charge regenerator for organic dye-sensitized solar cells (DSSCs). This solar cell generates electrical current in the process of oxidizing organic dyes back to their original shape.

Byung-Man Kim, another lead founder of the study, also noted that more current is generated due to the high connectivity of the large amount of charges in the organic dye to the surface state of Cs2SnI6. Therefore, Cs2SnI6 has a good level of charge acceptance in thermodynamics, and its photocurrent density is increased by 79% compared with the traditional liquid electrolyte.

This study, through the study of the charge transfer mechanism of Cs2SnI6, elucidated the function of its surface state, which attracted widespread attention in the research field. The results of this study suggest that in the presence of redox mediators, the surface state of Cs2SnI6 is the dominant charge transfer pathway, which should be considered in the design of future Cs2SnI6-based devices.