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Separating Electron and Hole Mobility in 3D Metal-Halide Perovskite

Nov. 21, 2019

Using transient reflectance (TR) spectroscopy, we measure the diffusion of carriers. The diffusion of carriers is limited by the slower of the two carriers (that is the ambipolar diffusion). Terahertz (THz) spectroscopy measures the sum of the carrier mobilities. Here we combine these two methods to detect both the electron and hole mobilities.

Scientific Achievement

We show how to extract both the electron and hole photo-induced carrier mobilities in a non-contact, all optical method.

Significance and Impact

Understanding how both the electron and hole mobilities vary with 3D thin-film perovskite processing conditions is essential for designing high-efficiency solar cells, LEDs, and photoelectrochemical cells.

Research Details

  • Perform time-resolved THz spectroscopy and TR spectroscopy and the same samples
  • THz spectroscopy is sensitive to the sum of the carrier mobilities (thus is sensitive to the larger of the two)
  • TR spectroscopy is sensitive to the ambipolar diffusion of the two carriers (thus, is sensitive to the smaller of the two).
  • Combining the two measurements yields both electron and hole mobilities
  • Find that the hole mobility is ~ 10x larger than electron.

DOI: 10.1021/acsenergylett.9b02310

Kai Zhu
National Renewable Energy Laboratory

Matthew Beard
National Renewable Energy Laboratory

Einstein relation equation, in ambipolar semiconductor equation, photconductivity equation, and sum mobility equation