The Importance
of Perovskite Pore Filling in Organometal
Mixed Halide Sensitized TiO<sub>2</sub>‑Based Solar Cells
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Abstract
Emerging from the field of dye-sensitized
solar cells, organometal
halide perovskite-based solar cells have recently attracted considerable
attention. In these devices, the perovskite light absorbers can also
be used as charge transporting materials, changing the requirements
for efficient device architectures. The perovskite deposition can
vary from merely sensitizing the TiO<sub>2</sub> electron transporting
scaffold as an endowment of small nanoparticles, to completely filling
the pores where it acts as both light absorber and hole transporting
material in one. By decreasing the TiO<sub>2</sub> scaffold layer
thickness, we change the solar cell architecture from perovskite-sensitized
to completely perovskite-filled. We find that the latter case leads
to improvements in device performance because higher electron densities
can be sustained in the TiO<sub>2</sub>, improving electron transport
rates and photovoltage. Importantly, the primary recombination pathway
between the TiO<sub>2</sub> and the hole transporting material is
blocked by the perovskite itself. This understanding helps to rationalize
the high voltages attainable on mesoporous TiO<sub>2</sub>-based perovskite
solar cells