All Solid‐State Flexible Electrochromic‐Organic Light‐Emitting Diode Devices on Single‐Plastic Substrate for See‐Through Display Technologies

Abstract

modulation of its transmittance states. The basic unit of an EC device consists of an electrolyte layer and two symmetric EC electrodes: cathodic and/or anodic EC film deposited on a conductive and transparent substrate. Upon application of an external potential the EC materials can undergo reversible changes of their optical absorption by redox processes and the simultaneous insertion/extraction (coloration/ decoloration) of charge-balancing ions. [10] With regard to the fabrication methods, the most part of the EC devices are typically assembled according to a "sandwichtype" structure, in which a liquid or gel electrolyte is interposed between the two EC electrodes. These systems however suffer from strong limitations, mainly due to defects in homogeneity of coloration, dark spots, and pinholes for the inhomogeneous distribution of the electric field applied, peripheral leakage for inefficient sealing, and, especially, a limited durability and lifetime. [1,11,12] Furthermore their use poses safety problems, requires a more complex sealing procedures and an additional lamination step of the two glass electrodes, limiting the speed of manufacturing process, and increasing costs. Therefore, a huge effort has been devoted to replace liquid and gel electrolytes with solid-state ones and at the same time design new and simplified device architectures. In this context, solid polymer electrolytes (SPEs) have gained great attention due their potential advantages, including electrochemical stability (e.g., wide electrochemical window), low-cost, and ease of processability. [13][14][15] In addition, they have high flexibility, are lightweight, have no leakage, and have good compatibility with electrode materials, making them suitable for scale-up to large area and the realization of multifunctional EC systems with integrative functionalities, such as for example photoelectrochromics or EC electroluminescent devices. [1,2,16] However, suitable ion conduction for EC application is achieved at the expense of their structural and mechanical properties, by adding organic solvents or plasticizing agents that can strongly affect the device stability. Furthermore, SPEs can be degraded by parasitic side reactions with air or moisture, and photo oxidative processes with consequent discoloration of the surface and mechanical damages, thus jeopardizing both the aesthetical and functional characteristics. Recently, two differentThe development of solid-state electrochromics (EC) represents an emerging challenge towards effective integration with other optoelectronic units, such as the EC-organic light-emitting diode devices (EC-OLEDs). By a simultaneous or independent control of optical contrast (EC function) and OLED emission upon electrical activation, these fascinating systems are capable of adaptively modulating solar radiation and display lighting. Here, we report a flexible ECOLED on a single-plastic substrate demonstrating how the rational design of a highly efficient and durable solid-state EC cell enables an increase of overa...

Enhanced Durability of an All-Solid-State WO3 Based Electrochromic Device on a Single Substrate by Using a Complementary Anodically Coloring Poly(o-ethoxyaniline)

“…Interestingly, we observed that direct vacuum deposition of WO 3 on a soft polymer substrate (Nafion) enabled the random packing of the WO 3 clusters playing a key role in the WO 3 pillar-like growth and the consequent structuring of the hybrid nanocomposite film. Recently, apart from demonstrating the integration of such a novel device with other optoelectronic units on a single substrate , and the scale-up on a large area, , we contextually observed that the introduction of different buffer layers at the anode consisting of ultrathin films of TiO 2 or SiO 2 , respectively, can effectively result in the cycling stability of this monolithic single-substrate device. , …”

“…Another fundamental and critical aspect for the realization of highly durable solid-state devices lies in the choice of the electrolyte component because it plays a pivotal role in the structural features and the overall stability of the device. − Among the different types, solid polymer electrolytes (SPEs) have gained major expectations for their potential advantages, among which are the wide electrochemical window, ease of processability, low cost, and low interfacial resistance over inorganic ceramic electrolytes. They also guarantee outstanding features of no leakage, high flexibility, light weight, and good compatibility with electrode materials, making them suitable for scale-up to a large area and for the integration with other optoelectronic units, such as a photovoltaic cell or organic light-emitting diode . However, SPEs generally suffer from lower conductivity than the liquid or gel counterparts, and most SPEs and gel electrolytes can be involved in degradative processes promoted by parasitic side reactions with air or moisture or subjected to photo-oxidative degradation by UV radiation or catalytic processes with the consequent discoloration of the surface and extensive mechanical damages, thus compromising their aesthetic and functional requirements.…”

“…They also guarantee outstanding features of no leakage, high flexibility, light weight, and good compatibility with electrode materials, making them suitable for scale-up to a large area and for the integration with other optoelectronic units, such as a photovoltaic cell or organic light-emitting diode. 26 However, SPEs generally suffer from lower conductivity than the liquid or gel counterparts, and most SPEs and gel electrolytes can be involved in degradative processes promoted by parasitic side reactions with air or moisture 27 or subjected to photo-oxidative degradation by UV radiation or catalytic processes with the consequent discoloration of the surface and extensive mechanical damages, thus compromising their aesthetic and functional requirements. To address these issues related to gel and liquid electrolytes, two main methodological approaches have been recently proposed.…”

“…Interestingly, we observed that direct vacuum deposition of WO 3 on a soft polymer substrate (Nafion) enabled the random packing of the WO 3 clusters playing a key role in the WO 3 pillar-like growth and the consequent structuring of the hybrid nanocomposite film. Recently, apart from demonstrating the integration of such a novel device with other optoelectronic units on a single substrate 26,42 and the scale-up on a large area, 39,40 we contextually observed that the introduction of different buffer layers at the anode consisting of ultrathin films of TiO 2 or SiO 2 , respectively, can effectively result in the cycling stability of this monolithic single-substrate device. 26,40 Herein, we developed a new EC anodic material and demonstrate how its use can reduce costs and further increase not only the EC performance and durability but also the processability if compared to other solid-state systems or similar devices with a buffer layer at the anode, such as SnO 2 , which requires a more complicated process and high production costs.…”

“…Recently, apart from demonstrating the integration of such a novel device with other optoelectronic units on a single substrate 26,42 and the scale-up on a large area, 39,40 we contextually observed that the introduction of different buffer layers at the anode consisting of ultrathin films of TiO 2 or SiO 2 , respectively, can effectively result in the cycling stability of this monolithic single-substrate device. 26,40 Herein, we developed a new EC anodic material and demonstrate how its use can reduce costs and further increase not only the EC performance and durability but also the processability if compared to other solid-state systems or similar devices with a buffer layer at the anode, such as SnO 2 , which requires a more complicated process and high production costs. A derivative of PANI, poly(o-ethoxyaniline) (POEA), was chosen because, apart from the fascinating EC coloration and the extraordinary anticorrosive and protective properties typical of PANI-based materials, it possesses easier processability, offering increased solubility in organic solvents and, in some cases, even in aqueous media and overcoming the main problems for practical applications of PANI, i.e., inadequate processability and insolubility in common organic solvents.…”