24.8%! Huadian refreshes the tiO2-based plane perovskite solar cell efficiency record

On August 3, 2022, the team of Professor Li Meicheng of North China Electric Power University published a research result entitled “24.8%-efficient planar perovskite solar cells via ligand-engineered TiO2 deposition” in the journal Joule.

This result proposes a TiO2 deposition strategy based on ligand engineering, which controls the water bath sedimentation process of TiO2 by introducing organic ligands in the TiO2 chemical water bath precursor, so as to achieve the preparation of TiO2 electron transport layer effectively applied to high-performance perovskite solar cells, and obtain a battery conversion efficiency of 24.8%, which is the highest value of the reported TiO2 base plane perovskite solar cell efficiency. The corresponding author of the paper is Professor Li Meicheng; The first authors are Huang Hao and Cui Peng.

In recent years, metal halide perovskite solar cells have developed rapidly and have received widespread attention. Among them, compared with mesoporous perovskite solar cells, planar perovskite solar cells have the advantages of simple structure and low temperature preparation, and show outstanding application potential in stacked cells and flexible batteries. In planar perovskite solar cells, as electron transport layers, titanium dioxide, tin oxide and zinc oxide have been deeply studied for their excellent photoelectric properties.

At present, planar perovskite solar cells based on tin oxide electron transport layers have achieved a certified efficiency of more than 25%. However, for titanium dioxide materials with earlier and richer reserves than tin oxide, the certification efficiency of the corresponding planar perovskite solar cells is still below 24%, far below the Shockley-Quisel limit. The above efficiency gap may be related to the quality of the titanium dioxide film and its interfacial contact with the perovskite film. Therefore, it is necessary to develop a strategy to precisely regulate the deposition process of titanium dioxide films to improve the quality of titanium dioxide films and their interfacial properties, thereby improving the efficiency of planar perovskite solar cells.

Professor Li Meicheng’s team proposed a TiO2 deposition strategy based on ligand engineering to achieve precise regulation of titanium dioxide deposition. Taking tartaric acid as an example, the ligand engineering deposition strategy can effectively inhibit the particle agglomeration on the surface of the TiO2 film and obtain a dense and flat electron transport layer. The smooth and smooth TiO2 surface ensures close contact with the perovskite film. In addition, the tartaric acid molecules attached to the surface of the TiO2 film can be bonded to the lead atoms at the bottom of the perovskite, thereby forming an interfacial crosslinking structure. The reliable interface contact and crosslinking structure effectively reduces the interface contact resistance and enhances the interface charge transmission. The further prepared planar perovskite solar cells obtained a photoelectric conversion efficiency of 24.8%, which is the highest value of the reported TiO2-based perovskite solar cell efficiency. In addition, the ultraviolet stability and humidity stability of TiO2-based perovskite solar cells have been effectively enhanced. The battery is placed in ambient air for 2000 h and can still maintain ~95% of its initial efficiency.

Figure 1: Study on the influence of ligand engineering deposition strategy on the surface micromorphology of TiO2.

Figure 2: Performance characterization of TiO2 films based on ligand engineering deposition.

Figure 3: Study on the effect of TiO2 on the growth of perovskite thin films and the study of interfacial structure.

Figure 4: Photoelectric conversion efficiency characterization of TiO2 base plane perovskite solar cells.

Figure 5: TiO2-based plane perovskite solar cell interface charge transfer characterization.

Figure 6: Battery device stability characterization.

This study proposes a ligand engineering deposition strategy to accurately adjust the TiO2 film and its interface structure, reduce the interfacial contact resistance of the battery, enhance the interfacial charge extraction, and achieve a significant improvement in the performance of TiO2-based perovskite solar cells, while effectively enhancing the ultraviolet stability and humidity stability. In addition, the ligand engineering deposition strategy proposed in this study can also be well applied to the preparation of other inorganic electron transport layers, such as tin oxide and zinc oxide, which provides more possibilities for promoting the development of photoelectric devices such as planar perovskite solar cells. (Source: Science Network)

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