Perovskite solar cells prepared via spray-deposition of the active layer have been realized, advancing this promising technology towards roll-to-roll compatible processing methods.

Spray‐coating is a versatile coating technique that can be used to deposit functional films over large areas at speed. Here, spray‐coating is used to fabricate inverted perovskite solar cell devices in which all of the solution‐processible layers (PEDOT:PSS, perovskite, and PCBM) are deposited by ultrasonic spray‐casting in air. Using such techniques, all‐spray‐cast devices having a champion power conversion efficiency (PCE) of 9.9% are fabricated. Such performance compares favorably with reference devices spin‐cast under a nitrogen atmosphere that has a champion PCE of 12.8%. Losses in device efficiency are ascribed to lower surface coverage and reduced uniformity of the spray‐cast perovskite layer.

These materials were fi rst explored in solar cells as recently as 2006 [ 1,2 ] and in solidstate solar cells as recently as 2012, [ 3,4 ] and have since seen an unprecedented increase in power conversion effi ciency (PCE). Building upon the initial results through device optimization and materials purifi cation, perovskite solar cells (PSCs) can now exhibit unstabilized PCEs in excess of 20%, signifi cantly outperforming competing classes of next generation photovoltaics. [ 5 ] In parallel with these developments, there has been a signifi cant improvement in the understanding of the physical properties of these materials. This not only includes the operating principles of different PSC architectures, but also fabrication methods compatible with large scale and low cost manufacturing. [6][7][8] Combining these factors, it is clear that organometal halide perovskites have signifi cant promise as a family of semiconductors for solar energy harvesting in commercial applications.To fabricate PSCs, a range of techniques have been employed for the deposition and formation of the light harvesting perovskite layer. These include vacuum deposition of the perovskite components [ 9 ] and solution deposition of perovskite precursor inks. [ 10 ] Two approaches can be adopted for solution deposition, commonly referred to as either "one-step" or "two-step" processing. In the one-step process, blends of a lead salt and an organic component (e.g., lead (II) chloride and methylammonium iodide) are dissolved in a common solvent such as dimethylformamide (DMF) or dimethyl sulfoxide and cast to form a thin fi lm, typically having a thickness of a few hundred nanometers. Following solution casting, thermal annealing is then used to create the perovskite structure. The simplicity of this approach has afforded the straightforward transfer of one-step processing from small area deposition methods (e.g., spin-casting) to techniques that are compatible with large-area substrates such as spray-coating [ 6,11 ] and inkjet printing. [ 12 ] In contrast, in the two-step process, a perovskite fi lm is formed via the initial deposition of a fi lm of a lead salt followed by its exposure to an organic halide, either in a vapor or a solution phase. [ 8,[13][14][15][16] Because both one-step and two-step procedures have been used to produce high performance PSCs, [16][17][18][19][20][21][22] both continue to be investigated in order to understand the basic mechanisms of perovskite formation and thus identify routes for further improvements in PSC effi ciency.Here, we characterize the formation of CH 3 NH 3 PbI 3− x Cl x via thermal annealing in air of a precursor fi lm prepared using the one-step procedure. A combination of 2D grazing incidence IntroductionIn recent years organometal halide perovskites have become the hot topic of solar cell research within the academic community. Grazing incidence wide and small angle X-ray scattering (GIWAXS and GISAXS) measurements have been used to study the crystallization kinetics of the organolead halide pero...

We review recent progress in the development of organometal halide perovskite solar cells. We discuss different compounds used to construct perovskite photoactive layers, as well as the optoelectronic properties of this system. The factors that affect the morphology of the perovskite active layer are explored, e.g. material composition, film deposition methods, casting solvent and various post-treatments. Different strategies are reviewed that have recently emerged to prepare high performing perovskite films, creating polycrystalline films having either large or small grain size. Devices that are constructed using meso-superstructured and planar architectures are summarized and the impact of the fabrication process on operational efficiency is discussed. Finally, important research challenges (hysteresis, thermal and moisture instability, mechanical flexibility, as well as the development of lead-free materials) in the development of perovskite solar cells are outlined and their potential solutions are discussed.

Synchrotron grazing incidence WAXS is used to track CH3NH3PbI3 precursor and perovskite crystallites rotation in situ during solution-deposition and thermal annealing.

Scanning nanofocus X-ray diffraction (nXRD) performed at a synchrotron is used to simultaneously probe the morphology and the structural properties of spin-coated CH 3 NH 3 PbI 3 (MAPI) perovskite films for photovoltaic devices. MAPI films are spin-coated on a Si/SiO 2 /poly(3,4-ethylenedioxythiophene): polystyrene sulfonate (PEDOT:PSS) substrate held at different temperatures during the deposition in order to tune the perovskite film coverage. The films are then investigated using nXRD and scanning electron microscopy (SEM). The advantages of nXRD over SEM and other techniques are discussed. A method to visualize, selectively isolate, and structurally characterize single perovskite grains buried within a complex, polycrystalline film is developed. The results of nXRD measurements are correlated with solar cell device measurements, and it is shown that spin-coating the perovskite precursor solution at elevated temperatures leads to improved surface coverage and enhanced solar cell performance.

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On page 8221, S. Lilliu and co‐workers show how synchrotron nXRD can be used to simultaneously probe the morphology and the structural properties of spin‐coated CH3NH3PbI3 perovskite films for photovoltaic devices. A method to visualize, selectively isolate, and structurally characterize single perovskite grains buried within a complex, polycrystalline film is developed.