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"One Arrow and Double Eagle" Strategy for Improving the Efficiency and Stability of Perovskite Solar Cells

2019-05-27 来源:亚科官网
 
Organic cations and halogen anion vacancy defects are the main factors that restrict the high efficiency and long-term stability of perovskite solar cells. How to eliminate these two defects at the same time is a difficult problem. Based on this, the research team of the researcher Zhou Huaiping of Peking University School of Engineering proposed a new elimination mechanism, which is to introduce fluoride into the active layer of perovskite, and to use the extremely high electronegativity of fluorine to achieve fluoride and form strong hydrogen with organic cations. The double effect of the bond and the formation of strong ionic bonds with lead ions. Thereby, the vacancy defects of the organic cation and the halogen anion are effectively eliminated, and the photoelectric conversion efficiency and long-term stability of the battery are greatly improved.
As an inexhaustible clean energy, solar energy has attracted the attention of researchers, and solar cells that convert solar energy into electric energy are also the research direction favored by many research groups in the world. In recent years, organic-inorganic hybrid perovskite solar cells have gained a lot of attention in academia and industry due to their high efficiency and low cost, and their photoelectric conversion efficiency has rapidly increased to 24.2% in just a few years. The most efficient thin film solar cell in a single cell.
However, the poor stability of such batteries is a major factor that seriously hampers their commercial application. Compared with traditional inorganic photovoltaic materials, the organic-inorganic hybrid perovskite material has a soft lattice and is an ionic crystal, which is easy to undergo ion migration under the interference of the external environment, forming a large number of vacancy defects, thereby inducing the lattice. The collapse and the decomposition of the components make it no longer have excellent photoelectric conversion capability.
Among many vacancy defects, halogen anions and organic cation vacancies are ubiquitous on the perovskite surface and grain boundaries due to their low defect formation energy. These two vacancy defects not only affect the solar cell's working efficiency, but also induce Further degradation of the perovskite crystals results in more bulk defects. The work previously reported for these two defects has focused on the passivation of a single defect, namely organic cations or halide vacancies, which cannot be "double-edged". How to eliminate these two defects at the same time and realize the further improvement of the efficiency and stability of the perovskite solar cell is the most difficult problem in the current research of perovskite materials.
In response to the above important issues, Zhou Huanping's group proposed a new elimination mechanism, which is to achieve the formation of strong hydrogen with organic cations by introducing sodium fluoride into the active layer of perovskite and utilizing the extremely high electronegativity of fluorine. The double effect of the bond and the formation of strong ionic bonds with lead ions. Based on the chemical bond modulation of the ionic bond and the hydrogen bond, the organic cation and the halogen anion in the perovskite component can be fixed, thereby eliminating the corresponding vacancy defects, and the battery efficiency and stability are significantly improved. The highest efficiency of the battery device introduced by sodium fluoride reached 21.92% (certified value was 21.7%), and there was no obvious hysteresis. At the same time, the device incorporating sodium fluoride exhibits excellent thermal stability and photostability. After a continuous light irradiation of the sun or heating at 85 °C for 1000 hours, the device can still maintain 95% and 90% of the original efficiency, respectively. Maintaining 90% of the original efficiency after 1000 hours of continuous operation at the maximum power point. The method solves two important factors limiting the stability of titanium ore solar cells: organic cations and halogen anion vacancies, and can be extended to other perovskite optoelectronic devices; and chemical bond modulation methods for other inorganic problems facing similar problems Semiconductor devices also have important reference significance.
Edited by Suzhou Yacoo Science Co., Ltd.