Spectrum-Dependent
Spiro-OMeTAD Oxidization Mechanism in Perovskite Solar Cells
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Abstract
We propose a spectrum-dependent mechanism
for the oxidation of 2,2′,7,7′-tetrakis(<i>N</i>,<i>N</i>-di-<i>p</i>-methoxyphenylamine)-9,9′-spirobifluorene
(Spiro-OMeTAD) with bis(trifluoromethane)sulfonimide lithium salt
(LiTFSI), which is commonly used in perovskite solar cells as the
hole transport layer. The perovskite layer plays different roles in
the Spiro-OMeTAD oxidization for various spectral ranges. The effect
of oxidized Spiro-OMeTAD on the solar cell performance was observed
and characterized. With the initial long-wavelength illumination (>450
nm), the charge recombination at the TiO<sub>2</sub>/Spiro-OMeTAD
interface was increased due to the higher amount of the oxidized Spiro-OMeTAD.
On the other hand, the increased conductivity of the Spiro-OMeTAD
layer and enhanced charge transfer at the Au/Spiro-OMeTAD interface
facilitated the solar cell performance