Perovskite-Sensitized Upconversion under Operando Conditions

Perovskite-sensitized upconversion (UC) has re-sulted 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 degrees 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.

Automated summary

This article investigates the effects of heat and light on the triplet generation process at the perovskite/rubrene interface. Exposure to these stressors resulted in local discrepancies across the upconversion device. Changes in morphology, degradation of organic layers, and reduction in triplet generation were observed in the first region, while no morphology changes and visible upconverted emission were observed in the second region. Transient absorption spectroscopy confirmed successful triplet generation even at elevated temperatures. This work emphasizes the challenges and potential of integrating perovskite-sensitized upconversion into commercial photovoltaic devices.