Large scale commercialization of perovskite solar cells requires to replace Pb with other element to improve the stability and reduce the toxicity. By employing laser initialized X-ray transient absorption spectroscopy, we have investigated the fate (relaxation, trapping, recombination etc.) of photoexcited charger carriers ~ 4 nm Cs3Bi2Br9 nanocrystals, a representative lead free perovskite. By selectively probing the Bi L3 edge and Br K X-ray absorptions, we have revealed that photoexcited electrons are mainly delocalized in the conduction band while the photogenerated holes are localized at Br 4p orbitals in the valence band, forming strong self-trapped exciton-polarons lasting for tens of ns. The kinetics study revealed that the detrapping of holes exhibits multiple mechanisms with different lifetimes.

Decipher electronic and structural evolution of lead-free perovskite using transient X-ray absorption spectroscopy

256th National Meeting (2018)

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