Scalable thin‐film deposition methods are increasingly important for hybrid lead halide perovskite thin films. Understanding the structure evolution during non‐equilibrium processes helps to find suitable materials and processing parameters to produce films with well‐performing optoelectronic properties. Here, spin‐cast and slot‐die coated bilayers of lead iodide (PbI2) and methylammonium iodide (MAI) are investigated by in situ grazing‐incidence wide‐angle X‐ray scattering during the thermal annealing process, which converts the bilayer into methylammonium lead iodide (MAPI). Photoluminescence (PL) and UV/Vis measurements show increasing crystallinity during the annealing process and a slight PL red‐shift of the spin‐cast film, attributed to crystallite coalescence that is not prominent for the slot‐die coated film. The disintegration of the solvent‐precursor complex (MA)2(Pb3I8) ⋅ 2 DMSO and conversion into perovskite are followed in situ and differences in the morphology and time evolution are observed. In both, spin‐cast and slot‐die coated thin‐films, the isotropic orientation is dominant, however, in the slot‐die coated films, the perovskite crystallites have an additional face‐on orientation ((110) parallel to substrate) that is not detected in spin‐cast films. An Avrami model is applied for the perovskite crystal growth that indicates reduced dimensionality of the growth for the printed thin films.

The superlattice in a quantum dot (QD) film on a flexible substrate deformed by uniaxial strain shows a phase transition in unit cell symmetry. With increasing uniaxial strain, the QD...

Thermocapillary convection on gasbubbles caused by temperature gradientsAbstract. The thermocapillary convection on free surfaces is an important mechanism for heat transfer, it is demonstrated in two experiments. Silicon-oil of various viscosity is used as experimental liquid. In the thermal stable stratified liquid air bubbles were injected. Around the bubbles velocity profiles, induced by the thermocapillary force against the buoyancy force were measured. In the second experiment the enhancement of heat transfer induced by air bubbles touching a heated wire is investigated in various liquids. In spite of the small contact area between the bubble and the wire the increase of heat transfer was more than twice of the wire without bubble which is attributed to the Marangoni convection. Using water this enhancement could not be observed. At the bubble the free convection from the wire was hindered and the heat reduced by 30%.Kurzfassung. Bei freien Grenzfl~chen spielt die thermokapillare Konvektion eine nicht zu vernachl/issigende Rolle auf den WS_rme-transport. In zwei Experimenten wird deren Einflul3 aufgezeigt. In SilikonSlen verschiedener Viskosit/it mit thermisch stabiler Schichtung werden Luftblasen eingebracht und das durch die thermokapillaren Kr/ifte gegen den Auftrieb erzeugte Geschwindigkeitsfeld vermessen. In einem zweiten Experiment wird die Erh6hung des W/irmefibergangs durch eine Luftbtase an einem beheizten Draht gemessen. Trotz kleiner Berfihrungsfl/iche kann der W/irme/ibergang gegenfiber dem Draht ohne Blase verdoppelt werden, was der zus/itzlichen Marangoni-Konvektion zuzuschreiben ist. In Wasser wurde dieser Effekt nicht beobachtet, hier wurde dutch die Luftblase der W/irmetibergang um 30% reduziert.