Effect of Yttrium-Incorporated TiO2 Electron Transport Layer on the Photovoltaic Performance of Triple-Cation Perovskite Solar Cells

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Achieving an excellent electron transport layer is significant for high-performance perovskite solar cells. A TiO 2 compact film is extensively applied as an electron transport layer. However, some limiting issues, such as unfavorable band offset, unsatisfactory electrical conductivity, low electron mobility, and high-density defects, remain in the TiO 2 electron transport layer. In this work, yttrium (Y) is proposed as a dopant in the TiO 2 electron transport layer. It is revealed that the incorporation of Y promotes the Fermi energy level of TiO 2 shift upward, bringing about more favorable energy-level alignment for the transport of photogenerated carriers. In addition, the device assembled with a Y-TiO 2 electron transport layer exhibits an increased built-in potential, suggesting a more powerful driving force for charge separation and transport. Eventually, the triple-cation perovskite solar cell equipped with a Y-TiO 2 electron transport layer acquires an efficiency of 20.09%. It is superior to that of the TiO 2 -based device (17.28%). The results indicate that Y-ion doping is a promising method to fabricate highly efficient perovskite solar cells.