Triplet-sensitization by lead halide perovskite thin films for near-infrared-to-visible upconversion

Lead halide-based perovskite thin films have attracted great attention due to the explosive increase in perovskite solar cell efficiencies. The same optoelectronic properties that make perovskites ideal absorber materials in solar cells are also beneficial in other light-harvesting applications and make them prime candidates as triplet sensitizers in upconversion via triplet-triplet annihilation in rubrene. In this contribution, we take advantage of long carrier lifetimes and carrier diffusion lengths in perovskite thin films, their high absorption cross sections throughout the visible spectrum, as well as the strong spin-orbit coupling owing to the abundance of heavy atoms to sensitize the upconverter rubrene. Employing bulk perovskite thin films as the absorber layer and spin-mixer in inorganic/organic heterojunction upconversion devices allows us to forego the additional tunneling barrier owing from the passivating ligands required for colloidal sensitizers. Our bilayer device exhibits an upconversion efficiency in excess of 3% under 785 nm illumination

Homogenization of Halide Distribution and Carrier Dynamics in Alloyed Organic-Inorganic Perovskites

Perovskite solar cells have shown remarkable efficiencies beyond 22%, through organic and inorganic cation alloying. However, the role of alkali-metal cations is not well-understood. By using synchrotron-based nano-X-ray fluorescence and complementary measurements, we show that when adding RbI and/or CsI the halide distribution becomes homogenous. This homogenization translates into long-lived charge carrier decays, spatially homogenous carrier dynamics visualized by ultrafast microscopy, as well as improved photovoltaic device performance. We find that Rb and K phase-segregate in highly concentrated aggregates. Synchrotron-based X-ray-beam-induced current and electron-beam-induced current of solar cells show that Rb clusters do not contribute to the current and are recombination active. Our findings bring light to the beneficial effects of alkali metal halides in perovskites, and point at areas of weakness in the elemental composition of these complex perovskites, paving the way to improved performance in this rapidly growing family of materials for solar cell applications.Comment: updated author metadat

Kulturen des Entscheidens

Der Band thematisiert Entscheiden als eine soziale Praxis, die keineswegs selbstverständlich sondern in hohem Maße voraussetzungsvoll ist und die mit unterschiedlichen Zumutungen einhergeht. Entscheiden nimmt je nach sozialen Umständen ganz unterschiedliche Formen an und unterliegt demnach dem historischen Wandel. Die Beiträge des Bandes gehen anhand ausgewählter Fallbeispiele, die vom mittelalterlichen Europa bis hin zum gegenwärtigen Indien reichen, unterschiedlichen Aspekten von Kulturen des Entscheidens nach. Sie nehmen Narrative und Praktiken des Entscheidens ebenso in den Blick wie den Einsatz von Ressourcen in Prozessen des Entscheidens und diskutieren Ansätze, Entscheiden in einer geistes- und kulturwissenschaftlichen Perspektive zu analysieren. Der Band zeigt so die vielfältigen Möglichkeiten auf, wie Entscheiden untersucht werden kann, wenn dieses als eine historisch wandelbare soziale Praxis und als kulturell diverses Phänomen begriffen wird

Literary Prizes. History, Theory and Practice

Nienhaus SA. Dennis Borghardt, Sarah Maaß, Alexandra Pontzen (Hg.): Literaturpreise. Geschichte, Theorie und Praxis. Würzburg, Königshausen & Neumann, 2020. Zeitschrift für Deutsche Philologie. 2022;141(4):622-626

Correction: Engineering 3D perovskites for photon interconversion applications.

[This corrects the article DOI: 10.1371/journal.pone.0230299.]

Engineering 3D perovskites for photon interconversion applications.

In this review, we highlight the current advancements in the field of triplet sensitization by three-dimensional (3D) perovskite nanocrystals and bulk films. First introduced in 2017, 3D perovskite sensitized upconversion (UC) is a young fast-evolving field due to the tunability of the underlying perovskite material. By tuning the perovskite bandgap, visible-to-ultraviolet, near-infrared-to-visible or green-to-blue UC has been realized, which depicts the broad applicability of this material. As this research field is still in its infancy, we hope to stimulate the field by highlighting the advantages of these perovskite nanocrystals and bulk films, as well as shedding light onto the current drawbacks. In particular, the keywords toxicity, reproducibility and stability must be addressed prior to commercialization of the technology. If successful, photon interconversion is a means to increase the achievable efficiency of photovoltaic cells beyond its current limits by increasing the window of useable wavelengths

Precharging Photon Upconversion: Interfacial Interactions in Solution-Processed Perovskite Upconversion Devices

Recent advances in perovskite-sensitized photon upconversion via triplet-triplet annihilation (TTA) in rubrene have yielded several unanswered questions about the underlying mechanism and processes occurring at the interface. In particular, the near-infrared perovskite emission is not significantly quenched and a rapid reversible photobleach of the upconverted emission can be observed under fairly low excitation densities of 3.2 mW/cm2. In this contribution, we investigate the perovskite/organic interface in more detail and conclude that non-covalent interactions between the organic layer and perovskite result in surface trap passivation. In addition, band bending results in a charge space region at the perovskite/rubrene interface, which precharges the rubrene interface with holes. Upon initial illumination, electrons can rapidly transfer to the excited triplet state of rubrene, followed by efficient TTA upconversion. As the device is continuously illuminated, the precharged holes are consumed and a new equilibrium is reached, resulting in the previously investigated steady-state upconversion efficiency.</p