posted on 2024-02-06, 15:48authored byGregory Moller, Colette M. Sullivan, Andrew P. Cantrell, Masoud Mardani, Alexander S. Bieber, Theo Siegrist, Lea Nienhaus
Perovskite-sensitized photon upconversion (UC) has the
potential
to improve a wide range of technologies including photocatalysis and
photovoltaics, by converting two low energy photons into a single
photon of higher energy. To date, perovskite-sensitized UC has been
studied by using nanocrystals in solution and solid-state thin film
bilayers using polycrystalline perovskite films. While efficient UC
has been achieved in thin film bilayers, surface inhomogeneities and
defects due to individual perovskite crystal grains and grain boundaries
may limit the overall performance. However, one of the main issues
in solid-state UC is a limited number of viable triplet annihilators
in the solid-state due to unfavorable intermolecular interactions
and competing relaxation pathways. Here, we investigate the properties
of mixed cation methylammonium formamidinium lead triiodide perovskite
single crystals using X-ray diffraction and optical spectroscopy and
their subsequent incorporation and performance as triplet sensitizers
for triplet–triplet annihilation in solution-based rubrene.
With the hybrid solid-state/solution approach presented here, a wide
number of potential annihilators can be rapidly be screened. In addition,
the higher surface homogeneity and orders of magnitude lower defect
densities and higher stability of perovskite single crystals allow
for potential improvements to interfacial charge transfer processes
and increases in UC performance due to reduced carrier trapping.