Solution Deposition Of Thin Films Research Articles

A Combinatorial Approach for the Solution Deposition of Thin Films

Optimization of thin film deposition is often the limiting step in the discovery of new materials and device development. Over the years, high-throughput combinatorial methods were developed for the deposition of thin films from the gas phase. However, very few reports focused on combinatorial thin film deposition from solution. Here, we introduce a combinatorial approach for the deposition of thin films from solution. The flow deposition setup allows for simultaneously studying the effect of two critical parameters, deposition time and deposition temperature, on a single sample. As a proof of concept, we demonstrate the solution deposition of PbS thin films, which resulted in a library of 25 deposition condition combinations on a single GaAs (100) substrate. X-ray diffraction and scanning electron microscopy combined with focused ion beam cross-sectional sample preparation confirmed the formation of high-quality PbS films and showed the morphology evolution as a function of these two deposition parameters. This method can be easily adapted for cost-effective and rapid combinatorial studies of a large variety of solution-deposited thin film materials.

Photovoltaic devices employing vacuum-deposited perovskite layers

Abstract

Chemical solution deposition of thin films for protonic ceramic fuel cells

Chemical solution deposition (CSD) offers the opportunity to fabricate very thin electrolyte films at lower temperatures than traditional powder-based methods. CSD methods have not been used much in production of protonic ceramic fuel cells (PCFC) until now. In this contribution we describe thin film deposition of the two proton-conducting materials BaZr0.9Y0.1O3 − δ (BZY) and La28 − xW4 + xO54 + δ (LWO) by spin coating. BZY films deposited on single-crystalline MgO grew epitaxially on the substrate. On a realistic PCFC cermet anode, 800 nm thick BZY films could be fabricated with a columnar structure which is promising to circumvent the low conductivity at grain boundaries of BZY. LWO films with some porosity were deposited on platinized Si from an aqueous solution.

Design and Synthesis of Molecular Donors for Solution-Processed High-Efficiency Organic Solar Cells

Organic semiconductors incorporated into solar cells using a bulk heterojunction (BHJ) construction show promise as a cleaner answer to increasing energy needs throughout the world. Organic solar cells based on the BHJ architecture have steadily increased in their device performance over the past two decades, with power conversion efficiencies reaching 10%. Much of this success has come with conjugated polymer/fullerene combinations, where optimized polymer design strategies, synthetic protocols, device fabrication procedures, and characterization methods have provided significant advancements in the technology. More recently, chemists have been paying particular attention to well-defined molecular donor systems due to their ease of functionalization, amenability to standard organic purification and characterization methods, and reduced batch-to-batch variability compared to polymer counterparts. There are several critical properties for efficient small molecule donors. First, broad optical absorption needs to extend towards the near-IR region to achieve spectral overlap with the solar spectrum. Second, the low lying highest occupied molecular orbital (HOMO) energy levels need to be between -5.2 and -5.5 eV to ensure acceptable device open circuit voltages. Third, the structures need to be relatively planar to ensure close intermolecular contacts and high charge carrier mobilities. And last, the small molecule donors need to be sufficiently soluble in organic solvents (≥10 mg/mL) to facilitate solution deposition of thin films of appropriate uniformity and thickness. Ideally, these molecules should be constructed from cost-effective, sustainable building blocks using established, high yielding reactions in as few steps as possible. The structures should also be easy to functionalize to maximize tunability for desired properties. In this Account, we present a chronological description of our thought process and design strategies used in the development of highly efficient molecular donors that achieve power conversion efficiencies greater than 7%. The molecules are based on a modular D(1)-A-D(2)-A-D(1) architecture, where A is an asymmetric electron deficient heterocycle, which allowed us to quickly access a library of compounds and develop structure-property-performance relationships. Modifications to the D1 and D2 units enable spectral coverage throughout the entire visible region and control of HOMO energy levels, while adjustments to the pendant alkyl substituents dictate molecular solubility, thermal transition temperatures, and solid-state organizational tendencies. Additionally, we discuss regiochemical considerations that highlight how individual atom placements can significantly influence molecular and subsequently device characteristics. Our results demonstrate the utility of this architecture for generating promising materials to be integrated into organic photovoltaic devices, call attention to areas for improvement, and provide guiding principles to sustain the steady increases necessary to move this technology forward.

Structural evolution of the KTa0.6Nb0.4O3 alkoxide-based solutions: probing the transition metals local environment by X-ray absorption spectroscopy

The KTa0.6Nb0.4O3 sols for chemical solution deposition of thin films were prepared from potassium acetate and transition metal ethoxides by the 2-methoxyethanol based route. The local environment of both transition metals after reflux times 1, 4, 24, and 48 h, whereby the crystallization behavior of the films was strongly affected, was monitored by extended X-ray absorption fine structure spectroscopy, at Ta L3 and Nb K edges. The Ta species existed in the sols as monomers, remaining stable even with prolonged reflux time. The Ta–O–K correlations were confirmed in all cases. In contrast, the Nb-alkoxide formed dimers, with a gradual formation of oligomeric species with prolonged refluxing. The Nb–O–K correlations were present after all reflux times. The number of K neighbours around Nb increased upon refluxing, saturating at 24 h.

Ink‐Jet Printing of In2O3/ZnO Two‐Dimensional Structures from Solution

In2O3–ZnO two‐dimensional (2D) structures were processed by ink‐jet printing and heating at 150°C and 450°C with the aim for implementation in transparent electronics. The In–Zn‐solution precursor, based on In‐alkoxide and Zn‐acetate in 2‐methoxyethanol, was originally designed for chemical solution deposition of thin films. To adapt it for piezoelectric ink‐jet printing, the viscosity and surface tension were adjusted by the addition of a more viscous 1,3‐propanediol. The optimum values were obtained for the ink consisting of 55 vol% of 1,3‐propanediol. The printing parameters including the temperatures of the cartridge and the substrate, and the drop spacing were adjusted to allow patterning with a 40 μm resolution on SiOx/Si and glass substrates. The ink‐jet‐printed 2D structures heated at 150°C were amorphous and according to infrared spectroscopy organics‐free, and upon heating at 450°C they crystallized without any preferential orientation, similarly as the spin‐coated thin films, which were studied as a reference.