Recently, the research group of Professor Chen Chong of Henan University published a research paper "Multifunctional CNT:TiO2 additives in spiro-OMeTAD layer for highly efficient and stable perovskite" solar cells. EcoMat 2021, 3, e12099", link to the article:
http://doi.org/10.1002/eom2.12099
At present, the efficiency of perovskite solar cells has been increased to 25.5%, but how to increase the efficiency while enhancing the stability of the cell is still a problem. Among high-efficiency perovskite solar cells, the most effective and commonly used hole transport material is spiro-OMeTAD. Because the hole mobility of spiro-OMeTAD is relatively low, in order to improve its conductivity, it is usually doped with lithium salt. However, after a long period of time, lithium salts tend to absorb moisture in spiro-OMeTAD, and lithium ions will undergo ion migration, resulting in a decrease in battery performance and stability. In response to these problems, recently, the Chen Chong research group of Henan University incorporated pure single-walled carbon nanotubes (CNT) and single-walled carbon nanotubes (CNT:TiO2) modified with titanium dioxide nanoparticles as additives into spiro-OMeTAD. The effects of two composite hole transport layers (ie spiro-OMeTAD+ CNT and spiro-OMeTAD+ CNT:TiO2) on battery performance and stability are discussed. The study found that due to the excellent conductivity and hydrophobicity of carbon nanotubes, the doped CNT and CNT:TiO2 can both improve the conductivity and hydrophobicity of the lithium salt-doped spiro-OMeTAD layer. More importantly, compared with CNT, the doped CNT:TiO2 can effectively improve the conductivity of the spiro-OMeTAD layer. This is mainly due to the strong interaction between the carbon atoms in CNT and the titanium atoms in TiO2 nanoparticles. , Resulting in a significant increase in the density of electronic states in CNT:TiO2, which is more conducive to charge transfer. At the same time, the calculation results also found that pure CNT has almost no effect on passivating the crystal defects in the perovskite, but the titanium and oxygen atoms in CNT:TiO2 can interact with the iodine and hydrogen atoms in the perovskite crystal. The formation of titanium-iodine bond and H...O hydrogen bond, thereby passivating the defect state of the perovskite, reducing the charge recombination at the perovskite/spiro-OMeTAD interface. In addition, n-type TiO2 nanoparticles may capture the photogenerated electrons transferred from the perovskite conduction band into the spiro-OMeTAD layer, reducing the leakage current of the battery. Finally, compared with CNT, CNT:TiO2 further optimizes the energy level structure of the perovskite/spiro-OMeTAD interface, and promotes the extraction and transfer of holes at the interface. Finally, due to the above advantages, the perovskite battery based on the spiro-OMeTAD + CNT:TiO2 composite hole transport layer shows better performance than the battery based on the CNT-doped spiro-OMeTAD and the undoped spiro-OMeTAD hole transport layer. High efficiency and stability.
This work was published in EcoMat, the flagship journal of new energy sources of Wiley Press. Qiang Lou, a graduate student of Henan University, is the first author, and Prof. Chong Chen is the only corresponding author of the paper. This work was supported by the research cooperation of Professor Huang Qingsong of Sichuan University, and was funded by the National Natural Science Foundation of China and the scientific and technological innovation talents of universities in Henan Province.
(A) The influence of battery structure and spiro-OMeTAD+CNT:TiO2 hole transport layer on battery performance, (b) the influence of CNT and CNT:TiO2 on battery stability.