• DOI:10.1126/science.1243982
• Corpus ID: 10314803

Electron-Hole Diffusion Lengths Exceeding 1 Micrometer in an Organometal Trihalide Perovskite Absorber

@article{Stranks2013ElectronHoleDL,
  title={Electron-Hole Diffusion Lengths Exceeding 1 Micrometer in an Organometal Trihalide Perovskite Absorber},
  author={Samuel D. Stranks and Giles E. Eperon and Giulia Grancini and Christopher Menelaou and Marcelo J P Alcocer and Tomas Leijtens and Laura M. Herz and Annamaria Petrozza and Henry J. Snaith},
  journal={Science},
  year={2013},
  volume={342},
  pages={341 - 344}
}

• S. Stranks, G. Eperon, +6 authors H. Snaith
• Published 18 October 2013
• Materials Science
• Science

Unrestricted Travel in Solar Cells In the past 2 years, organolead halide perovskites have emerged as a promising class of light-harvesting media in experimental solar cells, but the physical basis for their efficiency has been unclear (see the Perspective by Hodes). Two studies now show, using a variety of time-resolved absorption and emission spectroscopic techniques, that these materials manifest relatively long diffusion paths for charge carriers energized by light absorption. Xing et al. (p. 344) independently assessed (negative) electron and (positive) hole diffusion lengths and found them well-matched to one another to the ~100-nanometer optical absorption depth. Stranks et al. (p. 341) uncovered a 10-fold greater diffusion length in a chloride-doped material, which correlates with the material's particularly efficient overall performance. Both studies highlight effective carrier diffusion as a fruitful parameter for further optimization. Spectroscopy pinpoints facile carrier diffusion as a key factor in the efficiency of perovskite solar cells. [Also see Perspective by Hodes] Organic-inorganic perovskites have shown promise as high-performance absorbers in solar cells, first as a coating on a mesoporous metal oxide scaffold and more recently as a solid layer in planar heterojunction architectures. Here, we report transient absorption and photoluminescence-quenching measurements to determine the electron-hole diffusion lengths, diffusion constants, and lifetimes in mixed halide (CH3NH3PbI3-xClx) and triiodide (CH3NH3PbI3) perovskite absorbers. We found that the diffusion lengths are greater than 1 micrometer in the mixed halide perovskite, which is an order of magnitude greater than the absorption depth. In contrast, the triiodide absorber has electron-hole diffusion lengths of ~100 nanometers. These results justify the high efficiency of planar heterojunction perovskite solar cells and identify a critical parameter to optimize for future perovskite absorber development.