Perovskite-sensitized upconversion
(UC) has resulted
in near-infrared-to-visible
UC at solar-relevant fluxes. However, the successful implementation
of UC devices into operating solar cells will result in exposure to
similar environmental stressors as for the commercial photovoltaics
(PVs), mainly elevated temperatures, and continuous irradiation. In
this article, we investigated the effects of these two stressors,
heat and light, on the triplet generation process at the perovskite/rubrene
interface. Following exposure to both stressors, local discrepancies
across the upconversion device were discovered. The first region showed
changes to the morphology, and no detectable upconverted emission
was observed. Through the combination of optical microscopy and spectroscopy,
crystallization of the organic semiconductor layer, degradation of
dibenzotetraphenylperiflanthene, and concurrent degradation
of the perovskite sensitizer were found. These effects culminate in
a reduction in both triplet generation and triplet–triplet
annihilation. In the second region, no changes to the morphology were
present and visible UC emission was observed following exposure to
both stressors. To probe the triplet sensitization process at elevated
temperatures, transient absorption spectroscopy was performed. The
presence of the excited spin-triplet state of rubrene at 60 °C
highlighted successful triplet generation even at elevated temperatures.
This work emphasizes the challenges and continued potential for the
integration of perovskite-sensitized UC into commercial photovoltaic
devices.