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One of the major bottlenecks of perovskite photovoltaic modules fabrication is the homogeneous deposition of perovskite material on large-area substrates. Here, we show that slot-die coating technique combined with synergistic gas quenching and substrate heating can produce compact, homogenous and reproducible Cs0.16FA0.84Pb(I0·88Br0.12)3 perovskite films. We demonstrate the fabrication of perovskite solar cells (PSCs) in a planar (n-i-p) device configuration and attain power conversion efficiency (PCE) of 18% over 0.09 cm2 device active area. The versatility of this crystallization strategy, which eliminates the need for complex solvents or additive engineering, was studied using planar SnO2- and TiO2-coated FTO substrates. Our study provides greater insights into achieving controlled coating and homogeneous crystallization of perovskite films over large-area substrates (~10 × 10 cm2) necessary for the commercialization of this technology. Ministry of Education (MOE) Nanyang Technological University National Research Foundation (NRF) Submitted/Accepted version This research was supported by NTU start-up grant (M4081866), Ministry of Education (MOE) under AcRF Tier 2 grants (2018-T2-1-075 and 2019-T2-2-106) and National Research Foundation, Prime Minister’s Office, Singapore, under Energy Innovation Research Program (grant numbers: NRF2015EWT-EIRP003-004 and Solar CRP: S18-1176- SCRP). This research was supported by a CEA CTBU funding, under PTC PrintRose project, and by the IDEX Mobility grant from Grenoble Alpes University (Com-UGA).

In this work we study the electrical stability under both gate bias stress and gate and drain bias stress of short channel (L = 5 μm) bottom contact/top gate OTFTs made on flexible substrate with solution-processed organic semiconductor and fluoropolymer gate dielectric. These devices show high field-effect mobility (μFE> 1 cm2V−1s−1) and excellent stability under gate bias stress (bias stress Vds = 0V). However, after prolonged bias stress performed at high drain voltage, Vds, the transfer characteristics show a decreased threshold voltage, degradation of the subthreshold slope and an apparent increase in the field effect mobility. Furthermore, the output characteristics show an asymmetry when measured in forward and reverse mode. These experimental results can be explained considering that the bias stress induces the damage of a small part of the device channel, localized close to the source contact. The analysis of the experimental data through 2D numerical simulations supports this explanation showing that the electrical characteristics after bias stress at high Vds can be reproduced considering the creation of donor-like interface states and trapping of positive charge into the gate dielectric at the source end of the device channel. In order to explain this degradation mechanism, we suggest a new physical model that, assuming holes injection from the source contact into the channel in bounded polarons, envisages the defect creation at the interface near the source end of the channel induced by injection of holes that gained energy from both the high longitudinal electric fields and the polaron dissolution.

The performance of perovskite solar cells is under direct control of the perovskite film quality and controlling the crystalinity and orientation of solution-processed perovskite film is a fundamental challenge. In this study, we present a scalable fabrication process for heteroepitaxial growth of mixed-cation hybrid perovskites (FA(1-x-y)MA(x)Cs(y))Pb(I1-xBrx)(3) in ambient atmospheric condition by using a Crystal Engineering (CE) approach. Smooth and mesoporous thin film of pure crystalline intermediate phase of PbX2 center dot 2DMSO is formed by deposition of supersaturated lead/cesium halides solution. Kinetically fast perovskite nucleation is achieved by rapid intercalation of formamidinium iodide (FAI) and methylammonium bromide (MABr) into the intermediate layer trough solvent assisted S(N)1 ligand exchange. Finally, heteroepitaxially perovskite growth is accomplished via Volmer-Weber crystal growth mechanism. All the layers are deposited under atmospheric condition (relative humidity (RH) 50-75%) with high reproducibility for various device and module dimensions. In particular, perovskite solar modules (Pmax similar to 550 mW) are successfully fabricated by blade coating under atmospheric condition. The CE approach remarkably improves the device performance by reaching a power conversion efficiency of 18.4% for small area (0.1 cm(2)), 16.5% on larger area (1 cm(2)) devices, and 12.7% and 11.6% for blade-coated modules with an active area of 17 and 50 cm(2), respectively. Non-encapsulated triple cation solar cells and modules show promising stability under atmospheric shelf life and light soaking conditions.

We present a multitechnique investigation of the structural and electronic properties of the prototypical system composed by ultra-thin films of magnetic molecules [Co-tetraphenyl-porphyrins (Co-TPP)] grown on a ferromagnetic substrate [oxygen passivated Fe(0 0 1), namely the Fe(0 0 1)-p(1 × 1)O surface]. Low Energy electron diffraction (LEED) and scanning tunneling microscopy (STM), coupled with first-principles calculations, reveal the formation of a commensurate superstructure at monolayer coverage, made by a square array of flat-lying TPP molecules. UV–photoemission and inverse photoemission spectroscopies (UPS and IPES) are used to investigate their electronic structure. Similar to our previous results on the Zn–TPP growth on Fe(0 0 1)–p(1 × 1)O, the passivation of the metallic surface is able to preserve the photoemission features characteristic of quasi-free molecules, opening the route towards an exploitation of single oxide layers as protective films in organic/inorganic junctions. X-ray photoemission (XPS) and near edge X-ray adsorption fine structure spectroscopies (NEXAFS), are used to reveal the details of the Co–TPP interaction with the substrate., We acknowledge the CINECA award under the ISCRA initiative, for the availability of high performance computing resources and support (Application No. HP10C2SVDP).

Reflectance anisotropy spectroscopy (RAS) is a modulation optical spectroscopy that measures the difference in reflectance of two beams of linearly polarized light shining at near-normal incidence on a surface. It exploits the reduced symmetry of the surface or interface structure with respect to the underlying isotropic bulk. It was originally developed for investigating real surfaces in air and clean surfaces in ultrahigh vacuum (UHV), and then it has experienced a remarkable expansion in the last 20 years, being now applied to organic layers (in UHV and in air), in situ monitoring of semiconductor growth, controlled deposition of thin and ultrathin organic films, gas sensing, new carbon-based materials, and solid/liquid interfaces. This article covers a brief presentation of RAS, with instrumental details and interpretation of the experimental data. Some of the most significant and recent applications are reported.

We have grown (Y-Er)BaCuO superconducting thin films on SrTiO3, with thicknesses ranging from 250 to 7500 A. The superconducting films have been obtained from amorphous precursors deposited by rf magnetron sputtering from a single mosaic target made of (Y-Er), BaF2. An ex-situ annealing procedure has been used. The critical temperatures depend on their structural connectivity and thickness. The choice of performing the annealing ex-situ made possible to write, by using the electron beam lithography and the lift-off technique, test lines as narrow as 130. nm for the precursor film and useful bridges in the range of one micron for the annealed sample.