Realizing the commercialization of high-performance and robust perovskite solar cells urgently requires the development of economically scalable processing techniques. Here we report a highthroughput ultrasonic spray-coating (USC) process capable of fabricating perovskite film-based solar cells on glass substrates with power conversion efficiency (PCE) as high as 13%.Perovskite films with high uniformity, crystallinity, and surface coverage are obtained in a single step. Moreover, we report USC processing on TiO 2 /ITO-coated polyethylene terephthalate (PET) substrates to realize flexible perovskite solar cells with PCE as high as 8.1% that are robust under mechanical stress. In this case, a photonic curing technique was used to achieve a highlyconductive TiO 2 layer on flexible PET substrates for the first time. The high device performance and reliability obtained by this combination of USC processing with optical curing appears very promising for roll-to-roll manufacturing of high-efficiency, flexible perovskite solar cells. -halide perovskite solar cells, with power conversion efficiencies (PCEs) rapidly reaching circa 20%, 1-3 are one of the most promising, next-generation photovoltaic technologies due to their excellent material properties, including long carrier diffusion lengths 4 and large absorption coefficients. 5 To achieve high-quality perovskite films, a variety of deposition techniques, such as thermal evaporation, 6-8 single-step spin-coating, 9,10 layer-by-layer or two-step coating, 11,12 and vapor-assisted 13 processes have been developed. However, one major disadvantage of most laboratory-scale techniques is that they are incompatible with lowcost, roll-to-roll processing envisioned for large-scale manufacturing. Existing scalable processing techniques include ink-jet printing, slot-die coating, blade-coating, screen printing, and ultrasonic spray-coating. 14-21Among these cost-effective roll-to-roll compatible processes, ultrasonic spray-coating (USC) is one of the most promising that has been successfully exploited for the fabrication of various organic electronic devices including light emitting diodes, 22 photovoltaics, 23,24 photodetectors, 25 and field-effect transistors. 26 The overall advantage of USC is its ability to simultaneously provide high throughput, better control over directional deposition, efficient use of materials, uniform film coverage, compatibility with variety of substrates, with the potential for the deposition of continuous layers without dissolution of underlying layers. 23,[26][27][28] Recently, the USC process was demonstrated to deposit perovskite thin films on glass substrates, and the resulting devices showed an average PCE of 7. 8%. 29 However, considering the diverse application potential for thin film perovskites, it is highly important to demonstrate the fabrication of high-performance devices on light-weight and flexible substrates using scalable techniques. So far, one major challenge for the fabrication of solar cells on plastic substrates is their ...

We report on the microstructural and electrical properties of Mg-doped Ba0.6Sr0.4TiO3 thin films prepared by the metalorganic solution deposition technique using carboxylate-alkoxide precursors at a postdeposition annealing temperature of 750 °C. The structure and morphology of the films were analyzed by x-ray diffraction and atomic force microscopy studies. The electrical measurements were conducted on metal-ferroelectric-metal capacitors using Pt as the top and bottom electrode. The typical measured small signal dielectric constant and dissipation factor of undoped Ba0.6Sr0.4TiO3 thin films at a frequency of 100 kHz were 450 and 0.013, respectively. The undoped Ba0.6Sr0.4TiO3 thin films exhibited a high tunability of 28.1% and resistivity of 0.4×1012 Ω cm at an applied electric field of 200 kV/cm. The Mg-doped Ba0.6Sr0.4TiO3 thin films exhibited significantly improved dielectric loss and insulating characteristics compared to undoped Ba0.6Sr0.4TiO3 thin films. The effects of Mg doping on the microstructural, dielectric, and insulating properties of Ba0.6Sr0.4TiO3 thin films were analyzed. The high dielectric constant, low dielectric loss, high tunability, and low leakage current show the potential of pure and Mg-doped Ba0.6Sr0.4TiO3 thin films for integrated capacitor and microwave communication devices.

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Pure and La doped Ba0.6Sr0.4TiO3 thin (BST) films were fabricated via the metalorganic solution deposition technique using carboxylate-alkoxide precursors on Pt–Si substrates. The La doping concentration, from 0 to 10 mol %, was found to have a strong influence on the 750 °C postdeposition annealed films material properties. All films possessed a nontextured polycrystalline microstructure with no evidence of secondary phase formation. The pure and 1 mol % La doped films exhibited a uniform microstructure suggestive of a fully developed film at this annealing temperature. Improved dielectric and insulating properties were achieved for the 1 mol % La doped BST thin films with respect to that of undoped BST films. The 1 mol % La doped BST film exhibited a lower dielectric constant, (283 vs 450) and enhanced resistivity (31.4×1013 Ω cm vs 0.04×1013 Ω cm) with respect to that of undoped BST films. The loss tangent and tunability (at 100 kHz) of the 1 mol % La doped BST films were 0.019% and 21% (at E=300 kV/cm), respectively. Films doped at concentrations between 5 and 10 mol % possessed under developed microstructures suggesting that higher annealing temperatures and/or longer annealing times are required. The single phase structure of the 5–10 mol % La doped BST films, combined with the beneficial influence of the 1 mol % La doping on the BST films dielectric and insulating properties, suggest potential for further enhancement of the films material properties after optimization of the thermal treatments for the 5–10 mol % La doped BST thin films.

Polycrystalline SrTiO3 thin films having perovskite structure were prepared by the metallo-organic solution deposition technique on platinum coated silicon and bare silicon substrates. Crack free and crystalline films with uniform composition and thickness were fabricated by spinning and post deposition rapid thermal annealing at a low temperature of 550 °C for 60 s. The films exhibited good structural, dielectric, and insulating properties. The dielectric constant was found to depend on film thickness and annealing temperature. The small signal dielectric constant and dissipation factor at a frequency of 100 kHz were 225 and 0.008, respectively, for a 0.8-μm-thick film annealed at 700 °C for 60 s. The frequency dependence of the dielectric constant and the dielectric loss was also studied. The measurement of the current-voltage (I-V) characteristics on films in metal-insulator-metal configuration indicated the conduction process to be bulk limited. The I-V characteristics were ohmic at low fields and space-charge limited at high fields. Room temperature resistivity of 1013 Ω cm and leakage current density of less than 10−8 A/cm2 were obtained for a 0.8-μm-thick film at an applied electric field of 200 kV/cm, establishing good insulating behavior. The interfacial properties of gold-strontium titanate-silicon structures were studied experimentally by measuring the capacitance-voltage (C-V) characteristics. The C-V curves exhibited anomalous frequency dispersion behavior and a hysteresis phenomenon. The hysteresis in the C-V curve was found to be about 0.8 V and of a charge injection type. The density of interface states recharged during the bias cycle in hysteresis measurement was estimated to be of the order of 8.3×1011 cm−2. The density of interface states at the flatband voltage was found to have a value of 1.38×1012 eV−1 cm−2. For a 0.5-μm-thick SrTiO3 film, a unit area capacitance of 3.5 fF/μm2 and a charge storage density of 36.7 fC/μm2 were obtained at an applied electric field of 200 kV/cm. These measured parameters place SrTiO3 as one of the suitable dielectric material for dynamic random access memory applications.