High-Performance Perovskite Solar Cells and Modules Fabricated by Slot-Die Coating with Nontoxic Solvents.

Energy shortage has become a global issue in the twenty-firt century, as energy consumption grows at an alarming rate as the fossil fuel supply exhausts. Perovskite solar cells (PSCs) are a promising photovoltaic technology that has grown quickly in recent years. Its power conversion efficiency (PCE) is comparable to that of traditional silicon-based solar cells, and scale-up costs can be substantially reduced due to its utilization of solution-processable fabrication. Nevertheless, most PSCs research uses hazardous solvents, such as dimethylformamide (DMF) and chlorobenzene (CB), which are not suitable for large-scale ambient operations and industrial production. In this study, we have successfully deposited all of the layers of PSCs, except the top metal electrode, under ambient conditions using a slot-die coating process and nontoxic solvents. The fully slot-die coated PSCs exhibited PCEs of 13.86% and 13.54% in a single device (0.09 cm2) and mini-module (0.75 cm2), respectively.

The influence on surface characteristic and biocompatibility of nano-SnO2-modified titanium implant material using atomic layer deposition technique.

BACKGROUND/PURPOSE: To investigate the surface characteristics of titanium (Ti) implant materials, which were coated with different thicknesses of nanoscale tin oxide (SnO2) using the atomic layer deposition technique, and evaluated its biological performance on human embryonic palatal mesenchyme (HEPM) cells. METHODS: The thickness of the coating layer on Ti was 0 (Ti0), 20 nm (Ti20), 50 nm (Ti50), and 100 nm (Ti100), respectively. The surface morphology was observed with an SEM and AFM. The root mean square roughness of micron-scale (mRq) and nanoroughness (nRq) of Ti discs' surface were measured. The Alamar blue (AB) assay and F-actin fluorescence staining were used to evaluate the biocompatibility, and the osteocalcin (OCN) was measured to clarify the differentiation of HEPM cells on materials. RESULTS: In the coating groups, the mRq was decreased, but the nRq was increased. The spreading and polygonal morphology of HEPMs was apparent in coating groups. On Day 4, the survival rate of HEPM cells on Ti0 was higher than on Ti20 and Ti50. There was no significant difference on Day 7, Day 10, and Day 14. The OCN was significantly higher on Day 14 in all the coating groups than Ti0. CONCLUSION: The results showed that the cell growth was intensified with rough surfaces. However, the OCN and morphology change was prominent when the nanoroughness was increased, which meant the increased nanoroughness might enhance OCN production and improve the tendency of osseointegration. The nanoscale SnO2 coating could increase the ability of bone formation but not cell growth.

Nano-Laminated Metal Oxides/Polyamide Stretchable Moisture- and Gas-Barrier Films by Integrated Atomic/Molecular Layer Deposition.

Stretchable barrier films capable of maintaining high levels of moisture- and gas-barrier performance under significant mechanical strains are a critical component for wearable/flexible electronics and other devices, but realization of stretchable moisture-barrier films has not been possible due to the inevitable issues of strain-induced rupturing compounded with moisture-induced swelling of a stretched barrier film. This study demonstrates nanolaminated polymer/metal oxide stretchable moisture-barrier films fabricated by a novel molecular layer deposition (MLD) process of polyamide-2,3 (PA-2,3) integrated with atomic layer deposition (ALD) metal oxide processes and an in situ surface-functionalization technique. The PA-2,3 surface upon in situ functionalization with H2O2 vapor offers adequate surface chemisorption sites for rapid nucleation of ALD oxides, minimizing defects at the PA-2,3/oxide interfaces in the nanolaminates. The integrated ALD/MLD process enables facile deposition and precise structural control of many-layered oxide/PA-2,3 nanolaminates, where the large number of PA-2,3 nanolayers provide high tolerance against mechanical stretching and flexing thanks to their defect-decoupling and stress-buffering functions, while the large number of oxide nanolayers shield against swelling by moisture. Specifically, a nanolaminate with 72 pairs of alternating 2 nm (5 cycles) PA-2,3 and 0.5 nm HfO2 (five cycles) maintains its water vapor transmission rate (WVTR) at the 10-6 g/m2 day level upon 10% tensile stretching and 2 mm-radius bending, a significant breakthrough for the wearable/flexible electronics technologies.

Validated Analysis of Component Distribution Inside Perovskite Solar Cells and Its Utility in Unveiling Factors of Device Performance and Degradation.

Time-of-flight secondary-ion mass spectrometry (ToF-SIMS) has been used for gaining insights into perovskite solar cells (PSCs). However, the importance of selecting ion beam parameters to eliminate artifacts in the resulting depth profile is often overlooked. In this work, significant artifacts were identified with commonly applied sputter sources, i.e., an O2+ beam and an Ar-gas cluster ion beam (Ar-GCIB), which could lead to misinterpretation of the PSC structure. On the other hand, polyatomic C60+ and Ar+ ion beams were found to be able to produce depth profiles that properly reflect the distribution of the components. On the basis of this validated method, differences in component distribution, depending on the fabrication processes, were identified and discussed. The solvent-engineering process yielded a homogeneous film with higher device performance, but sequential deposition led to a perovskite layer sandwiched by methylammonium-deficient layers that impeded the performance. For device degradation, it was found that most components remained intact at their original position except for iodide. This result unambiguously indicated that iodide diffusion was one of the key factors governing the device lifetime. With the validated parameters provided, ToF-SIMS was demonstrated as a powerful tool to unveil the structure variation amid device performance and during degradation, which are crucial for the future development of PSCs.

Fabrication, Mechanisms, and Properties of High-Performance Flexible Transparent Conductive Gas-Barrier Films Based on Ag Nanowires and Atomic Layer Deposition.

Thin films of Ag nanowires (NWs) offer many advantages as transparent electrodes for flexible electronics, but their applications are hindered by issues including poor stability/durability of Ag NWs, high processing temperatures, heterogeneity of surfaces, and lack of gas-barrier function. This study reports novel mechanisms through which a conductive Hf:ZnO (HZO) film by atomic layer deposition (ALD) can be integrated with a sprayed Ag NWs film to address the issues of Ag NWs. First, the ALD surface reactions can induce fusing of the Ag NWs into a connected network without the need for a thermal sintering process. Second, the ALD process can in situ functionalize the Ag NWs to yield defect-free (in terms of blocking gas permeation) coverage of the ALD HZO over the entire nanowire surfaces, which also enhances the ALD-induced fusing of Ag NWs. The composite HZO/Ag NWs films exhibit low sheet resistance (15 Ω sq-1), low water vapor transmission rate (WVTR) (5.1 × 10-6 g m-2 day-1), high optical transmission (92%), excellent flexibility (12.5 mm bending radius), high stability/durability (against an extensive set of degradation modes and photolithographic patterning processes), and low processing temperature (90 °C) and can be used in perovskite solar cells to obtain high power conversion efficiency (14.46%).

Low-temperature gas-barrier films by atomic layer deposition for encapsulating organic light-emitting diodes.

Dependences of gas-barrier performance on the deposition temperature of atomic-layer-deposited (ALD) Al2O3, HfO2, and ZnO films were studied to establish low-temperature ALD processes for encapsulating organic light-emitting diodes (OLEDs). By identifying and controlling the key factors, i.e. using H2O2 as an oxidant, laminating Al2O3 with HfO2 or ZnO layers into AHO or AZO nanolaminates, and extending purge steps, OLED-acceptable gas-barrier performance (water vapor transmission rates ∼ 10-6 g m-2 d-1) was achieved for the first time at a low deposition temperature of 50 °C in a thermal ALD mode. The compatibility of the low-temperature ALD process with OLEDs was confirmed by applying the process to encapsulate different types of OLED devices, which were degradation-free upon encapsulation and showed adequate lifetime during accelerated aging tests (pixel shrinkage <5% after 240 h at 60 °C/90% RH).

Stable and High-Performance Flexible ZnO Thin-Film Transistors by Atomic Layer Deposition.

Passivation is a challenging issue for the oxide thin-film transistor (TFT) technologies because it requires prolonged high-temperature annealing treatments to remedy defects produced in the process, which greatly limits its manufacturability as well as its compatibility with temperature-sensitive materials such as flexible plastic substrates. This study investigates the defect-formation mechanisms incurred by atomic layer deposition (ALD) passivation processes on ZnO TFTs, based on which we demonstrate for the first time degradation-free passivation of ZnO TFTs by a TiO2/Al2O3 nanolaminated (TAO) film deposited by a low-temperature (110 °C) ALD process. By combining the TAO passivation film with ALD dielectric and channel layers into an integrated low-temperature ALD process, we successfully fabricate flexible ZnO TFTs on plastics. Thanks to the exceptional gas-barrier property of the TAO film (water vapor transmission rate (WVTR)<10(-6) g m(-2) day(-1)) as well as the defect-free nature of the ALD dielectric and ZnO channel layers, the TFTs exhibit excellent device performance with high stability and flexibility: field-effect mobility>20 cm2 V(-1) s(-1), subthreshold swing<0.4 V decade(-1) after extended bias-stressing (>10,000 s), air-storage (>1200 h), and bending (1.3 cm radius for 1000 times).

Atomic layer deposition of NiO hole-transporting layers for polymer solar cells.

NiO is an attractive hole-transporting material for polymer solar cells (PSCs) owing to its excellent stability and electrical/optical properties. This study demonstrates, for the first time, fabrication of uniform, defect-free, and conformal NiO ultra-thin films for use as hole-transporting layers (HTLs) in PSCs by atomic layer deposition (ALD) through optimization of the ALD processing parameters. The morphological, optical, and electrical properties of ALD NiO films were determined to be favorable for their HTL application. As a result, PSCs containing an ALD NiO HTL with an optimized thickness of 4 nm achieved a power conversion efficiency (PCE) of 3.4%, which was comparable to that of a control device with a poly(3,4-ethylenedioxy-thiophene):poly(styrene-sulfonate) HTL. The high quality and manufacturing scalability of ALD NiO films demonstrated here will facilitate the adoption of NiO HTLs in PSCs.

Air-stable flexible organic light-emitting diodes enabled by atomic layer deposition.

Organic light-emitting diodes (OLED) are an energy-efficient light source with many desirable attributes, besides being an important display of technology, but its practical application has been limited by its low air-stability. This study demonstrates air-stable flexible OLEDs by utilizing two atomic-layer-deposited (ALD) films: (1) a ZnO film as both a stable electron-injection layer (EIL) and as a gas barrier in plastics-based OLED devices, and (2) an Al2O3/ZnO (AZO) nano-laminated film for encapsulating the devices. Through analyses of the morphology and electrical/gas-permeation properties of the films, we determined that a low ALD temperature of 70 °C resulted in optimal EIL performance from the ZnO film and excellent gas-barrier properties [water vapor transmission rate (WVTR) <5 × 10(-4) g m(-2) day(-1)] from both the ZnO EIL and the AZO encapsulating film. The low-temperature ALD processes eliminated thermal damage to the OLED devices, which were severe when a 90 °C encapsulation process was used, while enabling them to achieve an air-storage lifetime of >10,000 h.

Transparent conductive gas-permeation barriers on plastics by atomic layer deposition.

A mixed-deposition atomic layer deposition process produces Hf:ZnO films with uniform dopant distribution and high electrical conductivity (resistivity = 4.5 × 10(-4) W cm), optical transparency (>85% from 400-1800 nm), and moisture-barrier property (water vapor transmission rate = 6.3 × 10(-6) g m(-2) day(-1)).

Interfacial energy levels and related properties of atomic-layer-deposited Al2O3 films on nanoporous TiO2 electrodes of dye-sensitized solar cells.

Low-temperature (approximately 150 degrees C), atomic-layer-deposited Al(2)O(3) films on nanoporous TiO2 electrodes of dye-sensitized solar cells (DSSCs) were investigated using electron spectroscopy. The power conversion efficiency (PCE) of the DSSCs was increased from 5.7% to 6.5%, an improvement of 14%, with one monolayer of Al(2)O(3) with a thickness of approximately 0.2 nm. The formation of Ti-O-Al(OH)(2) and interfacial dipole layers exhibited a strong influence on the work function of the Al(2)O(3) over-layers, while the thicker Al(2)O(3) over-layers caused the values of valence band maximum and band gap to approach the values associated with pure Al(2)O(3). A work function difference (Delta Phi(A-T)) of 0.4 eV and a recombination barrier height (epsilon(RB)) of 0.1 eV were associated with the highest PCE achieved by the first monolayer of the Al(2)O(3) layer. Thicker Al(2)O(3) over-layers, however, caused significant reduction of PCE with negative Delta Phi(T-A) and increased interfacial energy barrier height ((*)epsilon(IB)) between the N719 dyes and TiO2 electrodes. It was concluded that the PCE of the DSSCs may correlate with Delta Phi(A-T), epsilon(RB), and (*)epsilon(IB) resulting from various thicknesses of the Al(2)O(3) over-layers and that interfacial reactions, such as the formation of Ti-O-Al(OH)(2) and dipole layers, play an important role in determining the interfacial energy levels required to achieve optimal performance of dye-sensitized TiO2 solar cells.