Superior photo-carrier diffusion dynamics in organic-inorganic hybrid perovskites revealed by spatiotemporal conductivity imaging

The outstanding performance of organic-inorganic metal trihalide solar cells benefits from the exceptional photo-physical properties of both electrons and holes in the material. Here, we directly probe the free-carrier dynamics in Cs-doped FAPbI(3) thin films by spatiotemporal photoconductivity imaging. Using charge transport layers to selectively quench one type of carriers, we show that the two relaxation times on the order of 1 mu s and 10 mu s correspond to the lifetimes of electrons and holes in FACsPbI(3), respectively. Strikingly, the diffusion mapping indicates that the difference in electron/hole lifetimes is largely compensated by their disparate mobility. Consequently, the long diffusion lengths (3 similar to 5 mu m) of both carriers are comparable to each other, a feature closely related to the unique charge trapping and de-trapping processes in hybrid trihalide perovskites. Our results unveil the origin of superior diffusion dynamics in this material, crucially important for solar-cell applications.

Automated summary

The study directly probes the free-carrier dynamics in Cs-doped FAPbI(3) thin films using spatiotemporal photoconductivity imaging, revealing that the lifetimes of electrons and holes in the material are compensated by their disparate mobility, resulting in comparable long diffusion lengths for both carriers. This unique charge trapping and de-trapping processes in hybrid trihalide perovskites play a crucial role in determining the superior diffusion dynamics of the material, which is vital for solar-cell applications.