image: Strategy for the development of intrinsically stretchable optoelectronics, based on intrinsically stretchable materials and novel fabrication techniques. view more
Credit: OEA
A new publication from Opto-Electronic Advances; DOI 10.29026/oea.2022.210131 consider translating futuristic device concepts into practical applications.
Optoelectronic devices in stretchable formats have been extensively investigated to realize novel applications such as soft robotics, wearable optical sensors, wearable smart displays, and bio-integrated healthcare systems, which are difficult to achieve with the conventional rigid optoelectronic devices. The key technological advance required for this goal is to impart stretchability to the optoelectronic devices, and two approaches have been developed. The first approach takes advantage of the conventional, well-established inorganic materials by adopting “structures” that can be deformed, which resulted in the fabrication of stretchable optoelectronic devices with high performances.
The second approach is aimed at developing intrinsically-stretchable optoelectronic devices, using intrinsically-stretchable materials. Intrinsically-stretchable optoelectronic devices can endure mechanical deformations without additional structural engineering, and thus the device density can be preserved. Furthermore, the elimination of rigid device components is beneficial for bio-integrated optoelectronic applications, since the mechanical mismatch between the biological tissues and optoelectronic devices is minimized. However, the research on intrinsically-stretchable optoelectronic devices is still at its infancy, and significant improvements are required in terms of material synthesis for higher optical/electronic performance, and design/fabrication/integration technique for device/system development. The synthesis of novel soft optoelectronic materials is now being actively investigated, along with their application to device fabrication and system integration. For example, elastomeric composites composed of conducting/semiconducting fillers and elas Their processing techniques for the large-area fabrication of intrinsically-stretchable optoelectronic devices with high pixel density, large-areal coverage, and facile bio-integration with the human body are also being investigated with high interest.
In this review, the authors discuss the recent research efforts in developing intrinsically-stretchable optoelectronic devices ranging from materials synthesis to device fabrication. The basic building blocks of the intrinsically-stretchable optoelectronic devices are firstly described, with a focus on introducing functional elastomeric composites with intrinsic stretchability. Namely, the electronic fillers, elastomers, and surfactants used to develop the functional elastomeric composites are reviewed, along with their processing methods which are used to fabricate various devices. Then, the application of the functional elastomeric composites as the device components of the intrinsically-stretchable optoelectronic devices are described, while providing representative examples of intrinsically-stretchable optoelectronic devices, including light-emitting and light-absorbing devices, and some examples of intrinsically-stretchable integrated systems. Finally, the remaining challenges of intrinsically-stretchable optoelectronic devices are also presented.
The authors of this article review the recent advances in intrinsically-stretchable optoelectronic devices and systems, from the materials used to develop these devices to the fabrication techniques and integration strategies. Optoelectronic devices refer to electronic devices that can either convert light into electrical energy or emit light using electrical energy. Representative examples in real life include displays used in TVs/mobile devices/computers, image sensors used in cameras, and energy harvesting panels such as those used in solar photovoltaic power stations. Recently, optoelectronic devices in stretchable formats have been highlighted for their versatile applications, particularly for human-friendly applications such as wearable and/or implantable devices. For instance, personal biometric information can be continuously monitored with high accuracy by using wearable and/or implantable optical sensing systems. The measured physiological information can be used for real-time health monitoring and on-site diagnosis, which will be helpful for the early-diagnosis of many critical symptoms and the prevention of fatal health damages in the emergency situations. Such novel bio-integrated optoelectronic systems would provide new opportunities for remote diagnosis and ubiquitous healthcare.
To realize such applications, the stretchable optoelectronic devices must exhibit performance comparable to those of non-stretchable optoelectronic devices, especially in terms of key performance factors such as high areal coverage, high-quality light-emission, high-sensitivity photodetection, and high pixel resolution. However, stretchable optoelectronic devices based on inorganic rigid materials suffer from low device density, since the stretchability should be imparted by the space-consuming wavy-structured interconnects that effectively protect the active device against mechanical fractures. Furthermore, in the case of bio-integrated optoelectronic applications, the rigid device components can cause severe user discomfort owing to the mechanical mismatch with the soft biological tissues. On the other hand, stretchable optoelectronic devices fabricated from relatively soft materials, i.e., organic and polymeric materials, suffer from inferior device performances such as low photosensitivity. In this regard, substantial research efforts are now being devoted to developing intrinsically-stretchable materials with high optical/electrical performances, along with novel processing techniques for the device fabrication.
In this review, the recent efforts for developing intrinsically-stretchable optoelectronic devices and integrated systems are described. A special emphasis is given to functional elastomeric composites, which are used as the basic building blocks of intrinsically-stretchable optoelectronic device components such as the active layers (light-absorbing and light-emitting), charge-transport layers, and electrodes/interconnects. In specific, strategies for controlling the electrical, mechanical, and optical properties of the functional elastomeric composites are described, which is mainly achieved by varying characteristics of the filler material (e.g., dimension, electronic type, weight percent, and etc). The strategies for processing these materials for large-area fabrication, patterning for high device density and resolution, and integration with other stretchable devices for system development are also discussed. Actual examples of intrinsically-stretchable optoelectronic devices are reviewed, along with state-of-the-art system-level applications such as mobile healthcare systems. In all, the methods and strategies described in this review will be helpful in suggesting a new way for technological translation of intrinsically-stretchable optoelectronic device technology from academia to industry.
Article reference: Koo JH, Yun HW, Lee WC, Sunwoo SH, Shim HJ et al. Recent advances in soft electronic materials for intrinsically stretchable optoelectronic systems. Opto-Electron Adv 5, 210131 (2022). doi: 10.29026/oea.2022.210131
Keywords: stretchable optoelectronics / light-emitting capacitors / light-emitting diodes / photodetectors / photovoltaics / intrinsically stretchable devices
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Prof. Dae-Hyeong Kim’s group aims at developing high performance soft bio-integrated and bio-inspired electronic devices based on high-quality nanomaterials, which enable novel multifunctional biomedical and optoelectronic systems. The group’s first mission is to achieve significant improvement in current biomedical devices and/or to invent new unprecedented medical systems that innovate clinical procedures and surgeries with a purpose to help patients. Our devices can be integrated with the human body via fully-implantable, minimally-invasive, and skin-laminated modes, pursuing capabilities of high-resolution/-sensitivity health monitoring, real-time data storage/analysis/diagnosis, and feedback therapeutic stimulation/targeted drug delivery. The development of ultrathin and efficient power supply modules is another key technological interest. The second mission is to develop high-performance soft optoelectronic devices using quantum dot nanocrystals, perovskite thin films, two dimensional nanomaterials, and unconventional processing technologies. Device examples include the ultrathin and transparent display, curved image sensor array, and highly efficient photovoltaic devices.
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Opto-Electronic Advances (OEA) is a high-impact, open access, peer reviewed monthly SCI journal with an impact factor of 8.933 (Journal Citation Reports for IF2021). Since its launch in March 2018, OEA has been indexed in SCI, EI, DOAJ, Scopus, CA and ICI databases over the time and expanded its Editorial Board to 36 members from 17 countries and regions (average h-index 49).
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