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Optimizing bendability of flexible electronic devices using a neutral layer strategy

Majiaqi Wu, Maoliang Jian, Jianhua Zhang, Lianqiao Yang

2025, 1(4): 300-317. doi:10.1007/s44275-024-00019-8

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The neutral layer (NL) strategy is a key technique for improving the bendability of flexible electronic devices. In this study, by considering a three-layer structure as an example, the results obtained by finite element analysis (FEA) showed that the NL gradually moved to the top surface of the film as the film thickness and Young’s modulus increased, which are similar to the results produced by theoretical calculations. Subsequently, we optimized the thickness of a single NL structure and the failure bending radius of an indium tin oxide (ITO) electrode was reduced by 50% after optimization. In order to address the problems that affect the design of a single NL, we used optical clear adhesive (OCA) to generate multiple NLs. The FEA method was again applied to the structure and the results showed that decreasing the elastic modulus of the OCA and film thickness could reduce the maximum strain in the film. Finally, the effects of the OCA parameters on the protection of a multiple-layer ITO electrode structure were verified in bending experiments, which showed that the strain on ITO could be reduced from 5.6% to almost 0 in the two-electrode structure. The proposed strategies for designing single and multiple NLs can provide some guidance to facilitate optimizing the electronic infrastructure of flexible devices.

Flower-like GO-MoS₂ SERS platform for sensitive quantification of cortisol

Wenmiao Yu, Xuan Xu, Tingting Zheng

2025, 1(4): 318-326. doi:10.1007/s44275-024-00024-x

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Mental stress is a dangerous factor for the health of living beings, which can lead to various diseases. However, currently, there is a lack of diagnostic tools that can quickly and accurately quantify levels of mental stress. Cortisol is an important stress hormone that is widely present in bodily fluids; its concentration can reflect the level of mental stress in organisms. Here, we report a surface-enhanced Raman spectroscopy (SERS) probe based on flower-like graphene oxide-molybdenum disulfide composite material functionalized with cortisol DNA recognition element and tetracyanoquinodimethane of Raman label, with a remarkable enhancement factor value of 7.38 × 10⁵, which exhibits excellent cortisol detection ability in a wide range of concentrations from 1 nM to 1 000 nM, with the limit of detection down to 0.773 nM. The whole detection takes only 20 min. In addition, the SERS probe can selectively detect cortisol in other substances with similar chemical structures, which makes the probe applicable to complex biological systems with good reproducibility and stability. This designed SERS probe has been successfully employed in the detection of mouse serum cortisol, with high accuracy compared with enzyme-linked immunosorbent assay (ELISA) results, demonstrating great potential in actual biological sample detection.

Rationally tailored passivation molecules to minimize interfacial energy loss for efficient perovskite solar cells

Taoran Geng, Jike Ding, Zuolin Zhang, Mengjia Li, Hongjian Chen, Thierry Pauporté, Rundong Wan, Jiangzhao Chen, Cong Chen

2025, 1(4): 327-338. doi:10.1007/s44275-025-00026-3

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Labor-intensive, trial-and-error methods are frequently employed for modifying the perovskite surface to mitigate trap defects. There is an urgent need for rationally designed and efficient molecular passivators. To address the performance and stability challenges caused by defects in polycrystalline perovskite, we have rationally designed and tailored passivation molecules, 4-(trifluoromethyl)benzoic anhydride (TFBA), ethyl 4-(trifluoromethyl)benzoate (TFB), and 4-(trifluoromethyl)benzoic acid (PTF), to minimize interfacial energy loss and modulate the bandgap alignment for achieving efficient perovskite solar cells (PSCs). These molecules could target the perovskite surface defects, particularly Pb–I antisite defects, with the –COOH and trifluoromethyl functional groups at the edges. Among them, PTF exhibited superior passivation performance by coordinating its carboxyl group with Pb²⁺, effectively suppressing non-radiative recombination. Additionally, the fluorine sites in these molecules corrected lattice distortions and stabilized the perovskite structure through hydrogen bonding with MA/FA cations, reducing ion migration, and enhancing moisture resistance. As a result, PTF-modified PSCs achieved an efficiency of 25.57% and maintained over 85% of their initial efficiency after 1 600 h of aging. This study provides a clear pathway for optimizing passivation strategies through rational molecular design.

Low-dimensional organic semiconductor crystals for advanced photonics

Linqing Qiu, Qiang Lv, Xuedong Wang

2025, 1(4): 339-355. doi:10.1007/s44275-024-00010-3

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In the domain of information processing, communication technology, and computation, the utilization of photons as vectors for information is a critical innovation. Photonic integrated circuits (PICs) are specifically designed to control and transmit light, thereby facilitating the conveyance of data. The recent surge in interest in low-dimensional organic semiconductor crystals is attributed to their unique size-tunable properties and customizable physicochemical characteristics. These features position them as prime candidates for constructing the next generation of high-performance optoelectronic devices. The discourse presented elaborates on the progress in four pivotal areas concerning low-dimensional organic semiconductor crystals: optical generation, optical transportation, optical signal conversion and optical detection. These facets are integral to PICs because they underpin the fundamental mechanisms through which information is transmitted and manipulated via photons. Despite the promising attributes associated with these low-dimensional organic semiconductors, there remain considerable challenges to integrating these materials into the photonic constituents of PICs in a manner that is both effective and scalable. The text culminates with a concise summary and a forward-looking perspective on the potential applications and future development of low-dimensional organic semiconductor crystals within the sphere of advanced photonics. This outlook considers ongoing research and the anticipated breakthroughs that could further enhance the role of these materials in the evolution of photonic technologies.

Wearable self-powered devices based on polymer thermoelectric materials

Yi Yang, Hui Li, Zhen Xu, Siyi Luo, Lidong Chen

2025, 1(4): 356-369. doi:10.1007/s44275-024-00020-1

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Driven by rapid advances in the thermoelectric (TE) performance of organic materials, conjugated polymer thermoelectric (PTE) materials are considered ideal candidates for flexible self-powered devices because of their intrinsic flexibility, tailored molecular structure, large-area solution processability, and low thermal conductivity. One promising application is the flexible and wearable TE devices used on the human body to convert human energy (human motion or body heat) into electricity. The self-powered character with extended functions allows PTE devices to monitor human activity or health status. In this review, we first introduce existing high-performance PTE materials and the architectures of PTE devices. Then, we focus on the progress of research on flexible self-powered devices based on PTE materials, including TE generators, TE sensors, and Peltier coolers. Finally, possible challenges in the development of PTE devices are discussed.

GaN-on-diamond technology for next-generation power devices

Kangkai Fan, Jiachang Guo, Zihao Huang, Yu Xu, Zengli Huang, Wei Xu, Qi Wang, Qiubao Lin, Xiaohua Li, Hezhou Liu, Xinke Liu

2025, 1(4): 370-394. doi:10.1007/s44275-024-00022-z

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Gallium nitride (GaN)-based power devices have attracted significant attention due to their superior performance in high-frequency and high-power applications. However, the high-power density in these devices often induces severe self-heating effects (SHEs), which degrade their performance and reliability. Traditional thermal management solutions have struggled to efficiently dissipate heat, thereby leading to suboptimal real-world performance compared with theoretical predictions. To address this challenge, diamond has emerged as a highly promising substrate material for GaN devices, primarily due to its exceptional thermal conductivity and mechanical stability. GaN-on-diamond technology has a thermal conductivity of 2 200 W/m/K and it significantly enhances heat dissipation at the chip level. In this review, we provide a systematic overview of the two main integration methods for GaN and diamond: bonding and epitaxial growth techniques. Moreover, we elaborate on the impact of thermal boundary resistance (TBR) at the interface. According to the diffuse mismatch model, the TBR of GaN-on-diamond interfaces can be as low as 3 m²K/GW, which is markedly superior to silicon carbide substrates. In addition, novel techniques such as patterned growth, nanocrystalline diamond (NCD) capping films, and diamond passivation layers have been explored to further enhance thermal management capabilities. We also consider the roles of intermediate dielectric layers in reducing TBR, promoting diamond nucleation, and protecting the GaN layer. Thus, in this review, we summarize the current state of research into GaN-on-diamond technology, highlighting its revolutionary impact on thermal management for power devices and providing new pathways for the development of high-power GaN devices in the future.

Advanced growth techniques and challenges in ferroelectric AlScN thin films for next-generation electronic devices

Xiaoxi Li, Yuan Fang, Yuchun Li, Zhifan Wu, Shuqi Huang, Yingguo Yang, Bitao Dong, Gengsheng Chen, Yue Hao, Genquan Han

2025, 1(4): 395-409. doi:10.1007/s44275-024-00021-0

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The discovery of ferroelectricity in aluminum scandium nitride (AlScN) thin films has garnered significant research interest, owing to the large remnant polarization, tunable coercive field, excellent thermal stability, high breakdown field, and compatibility with back-end-of-line processes of these thin films. These attributes make AlScN a highly promising candidate for next-generation electronic device applications. Various techniques, such as reactive magnetron sputtering, radiofrequency sputtering, molecular beam epitaxy, metal-organic chemical vapor deposition, and pulsed laser deposition, have been employed to grow ferroelectric AlScN thin films. Critical growth parameters, including deposition atmosphere, precursor selection, and Sc concentration, strongly influence the ferroelectric properties, playing a crucial role in achieving high crystalline quality. This review critically examines the fabrication techniques used for producing ferroelectric AlScN thin films, focusing on the impact of different growth methods and process conditions on their properties. We aim to provide comprehensive guidance to assist future researchers in optimizing their process parameters to achieve the desired ferroelectric characteristics in AlScN thin films.

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