Atomic-Layer-Deposited SiOx/SnOx Nanolaminate Structure for Moisture and Hydrogen Gas Diffusion Barriers

Advancements in atomic-scale interface engineering for flexible electronics: enhancing flexibility and durability

Flexible electronics, such as wearable displays, implantable electronics, soft robots, and smart skin, have garnered increasing attention. Despite notable advancements in research, a bottleneck remains at the product level due to the prevalent use of polymer-based materials, requiring encapsulation films for lifespan extension and reliable performance. Multilayer composites, incorporating thin inorganic layers to maintain low permeability towards moisture, oxygen, ions, etc, exhibit potential in achieving highly flexible barriers but encounter challenges stemming from interface instability between layers. This perspective offers a succinct review of strategies and provides atomic-scale interface modulation strategy utilizing atomic layer integration technology focused on enhancing the flexibility of high-barrier films. It delves into bendable multilayers with atomic-scale interface modulation strategies, encompassing internal stress and applied stress modulation, as well as stretchable composite structural designs such as gradient/hybrid, wavy, and island. These strategies showcase significant improvements in flexibility from bendable to stretchable while maintaining high barrier properties. Besides, optimized manufacturing methods, materials, and complex structure design based on atomic-scale interface engineering are provided, better aligning with the future development of flexible electronics. By laying the groundwork for these atomic-scale strategies, this perspective contributes to the evolution of flexible electronics, enhancing their flexibility, durability, and functionality.

Electron Transport Layer Engineering Induced Carrier Dynamics Optimization for Efficient Cd-Free Sb2 Se3 Thin-Film Solar Cells

Antimony selenide (Sb2 Se3 ) is a highly promising photovoltaic material thanks to its outstanding optoelectronic properties, as well as its cost-effective and eco-friendly merits. However, toxic CdS is widely used as an electron transport layer (ETL) in efficient Sb2 Se3 solar cells, which largely limit their development toward market commercialization. Herein, an effective green Cd-free ETL of SnOx is introduced and deposited by atomic layer deposition method. Additionally, an important post-annealing treatment is designed to further optimize the functional layers and the heterojunction interface properties. Such engineering strategy can optimize SnOx ETL with higher nano-crystallinity, higher carrier density, and less defect groups, modify Sb2 Se3 /SnOx heterojunction with better interface performance and much desirable "spike-like" band alignment, and also improve the Sb2 Se3 light absorber layer quality with passivated bulk defects and prolonged carrier lifetime, and therefore to enhance carrier separation and transport while suppressing non-radiative recombination. Finally, the as-fabricated Cd-free Mo/Sb2 Se3 /SnOx /ITO/Ag thin-film solar cell exhibits a stimulating efficiency of 7.39%, contributing a record value for Cd-free substrate structured Sb2 Se3 solar cells reported to date. This work provides a viable strategy for developing and broadening practical applications of environmental-friendly Sb2 Se3 photovoltaic devices.

Complete stress release in monolayer ALD-Al2O3 films based on mechanical equilibrium homeostasis to realize a bending radius of 1 mm

Low-temperature-deposited, transparent, high-barrier-performance atomic layer deposition (ALD) Al₂O₃ films are widely utilized to protect organic optoelectronic devices. However, because the internal compression residual stresses result in poor mechanical properties, these films are unable to realize independent encapsulation. In this work, we propose a pre-bending and substrate thermal expansion process to fabricate low-residual-stress ALD-Al₂O₃ films by multistep adjustment of mechanical equilibrium homeostasis, compare and analyze the key properties of the films to determine the optimal processing conditions, and adjust the surface area differences between the film and the substrate to acquire a flat-bottom encapsulation substrate. Therefore, fewer cracks form in ALD-Al₂O₃ deposited at 40 °C, and no significant increase in the water-vapor-transmission rate (WVTR) occurred after multiple bending processes at a 3 mm radius. Furthermore, both the bending radius for the first crack generation and crack saturation density were optimal, resulting in excellent mechanical stability, and a bending radius of 1 mm was achieved. Finally, we confirm the feasibility of the monolayer ALD-Al₂O₃ prepared by our process for applications in OLEDs. The encapsulated OLED maintained 94% of its initial efficiency after 10 days of bending in a harsh environment at 30 °C and 90% relative humidity.