We report on an experiment with perovskite and organic solar cells on board of a rocket flight, reaching satellite altitudes for the first time. The electrical characterization during flight demonstrated in situ their functionality and power generation under space conditions. Perovskite and organic solar cells exceeded power densities of 14 and 7 mW cm À2 , respectively, highlighting their potential for an application in space.

Extensive studies have focused on improving the operational stability of perovskite solar cells but few surveyed the fundamental degradation mechanisms. One aspect overlooked in earlier works is the effect of the atmosphere on the device performance during operation.Here, we investigate the degradation mechanisms of perovskite solar cells operated under vacuum and a nitrogen atmosphere using synchrotron radiation-based operando grazingincidence X-ray scattering methods. Unlike what was seen in previous reports, we find that light-induced phase segregation, lattice shrinkage, and morphology deformation occur under vacuum. Under nitrogen, only lattice shrinkage appears during the operation of solar cells resulting in a better device stability. The different behavior in nitrogen is attributed a larger energy barrier for lattice distortion and phase segregation. Finally, we find that the migration of excessive PbI2 to the interface between the perovskite and the hole transport layer degrade the performance of devices either under vacuum or nitrogen.3 Solution-processed hybrid halide perovskite materials have attracted strong interest for next-generation thin-film photovoltaic applications due to their high power conversion efficiency (PCE) and low fabrication costs compared to silicon photovoltaics 1 . With solvent engineering, compositional tuning, and surface passivation 2-4 , the highest PCE of perovskite solar cells (PSCs) has reached 25.5 % 5 . Moreover, possibility of fabricating PSCs on flexible substrates opens up promising manufacturing routes, and novel application fields are explored, such as lightweight photovoltaic devices for space applications. Previous studies showed that PSCs were successfully operated in space with low vacuum conditions such as on a highaltitude balloon and a suborbital rocket [6][7][8] . Although these pioneers confirmed the possibility of operating PSCs in space, the operational stability of PSCs is unknown under such conditions.In terrestrial studies, vacuum conditions play a major role in the performance loss of PSCs during operation. Thus, although there is such a rapid increase in the PCE, very significant challenges remain. More research is required to increase the stability of the materials and the longevity of the devices, as long-term operational stability remains the main challenge for realworld applications of hybrid halide perovskite materials. Therefore, investigating the performance degradation mechanism of PSCs under different atmospheric conditions is one key approach to further improving the long-term operational stability of PSCs 9 .Exposure to above-bandgap illumination can cause a loss of phase and structure stability for perovskite materials. For instance, phase segregation introduced by lattice distortion, halide migration, and crystalline reorganization can cause an open-circuit voltage penalty arising from halide segregation 10 . In addition, several studies have indicated that a lattice distortion under illumination originates from light excitation or therm...

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.

Slot‐die coating is a powerful method for upscaling the production of organic solar cells (OSCs) with low energy consumption print processes at ambient conditions. Herein, chlorobenzene (CB) and chloroform (CF) are compared as host solvents for printing films of the neat novel fused‐ring unit based wide‐bandgap donor polymer (PDTBT2T‐FTBDT), the small molecule nonfullerene acceptor based on a fused ring with a benzothiadiazole core (BTP‐4F) as well as the respective PDTBT2T‐FTBDT:BTP‐4F blend films at room temperature in air. Using CF printing of the PDTBT2T‐FTBDT:BTP‐4F active layer, OSCs with a high power conversion efficiency of up to 13.2% are reached in ambient conditions. In comparison to CB printed blend films, the active layer printed out of CF has a superior morphology, a smoother film surface and a more pronounced face‐on orientation of the crystallites, which altogether result in an enhanced exciton dissociation, a superior charge transport, and suppressed nonradiative charge carrier recombination. Based on in situ studies of the slot‐die coating process of PDTBT2T‐FTBDT, BTP‐4F, and PDTBT2T‐FTBDT:BTP‐4F films, the details of the film formation kinetics are clarified, which cause the superior behavior for CF compared to CB printing due to balancing the aggregation and crystallization of donor and acceptor.

In situ printing gives insight into the evolution of morphology and optical properties during slot-die coating of active layers for application in organic solar cells and enables an upscaling and optimization of the thin film deposition process and the photovoltaic performance. Active layers based on the conjugated polymer donor with benzodithiophene units PBDB-T-2Cl and the non-fullerene small-molecule acceptor IT-4F are printed with a slot-die coating technique and probed in situ with grazing incidence small-angle X-ray scattering, grazing incidence wide-angle X-ray scattering, and ultraviolet/visible light spectroscopy. The formation of the morphology is followed from the liquid state to the final dry film for different printing conditions (at 25 and 35 °C), and five regimes of film formation are determined. The morphological changes are correlated to changing optical properties. During the film formation, crystallization of the non-fullerene small-molecule acceptor takes place and polymer domains with sizes of some tens of nanometers emerge. A red shift of the optical band gap and a broadening of the absorbance spectrum occurs, which allow for exploiting the sun spectrum more efficiently and are expected to have a favorable effect on the solar cell performance.