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- ItemSymmetry‐Induced Selective Excitation of Topological States in Su–Schrieffer–Heeger Waveguide Arrays(Weinheim : Wiley-VCH, 2023) Tang, Min; Wang, Jiawei; Valligatla, Sreeramulu; Saggau, Christian N.; Dong, Haiyun; Saei Ghareh Naz, Ehsan; Klembt, Sebastian; Lee, Ching Hua; Thomale, Ronny; van den Brink, Jeroen; Fulga, Ion Cosma; Schmidt, Oliver G.; Ma, LiboThe investigation of topological state transition in carefully designed photonic lattices is of high interest for fundamental research, as well as for applied studies such as manipulating light flow in on-chip photonic systems. Herein, the topological phase transition between symmetric topological zero modes (TZM) and antisymmetric TZMs in Su–Schrieffer–Heeger mirror symmetric waveguides is reported. The transition of TZMs is realized by adjusting the coupling ratio between neighboring waveguide pairs, which is enabled by selective modulation of the refractive index in the waveguide gaps. Bidirectional topological transitions between symmetric and antisymmetric TZMs can be achieved with proposed switching strategy. Selective excitation of topological edge mode is demonstrated owing to the symmetry characteristics of the TZMs. The flexible manipulation of topological states is promising for on-chip light flow control and may spark further investigations on symmetric/antisymmetric TZM transitions in other photonic topological frameworks.
- ItemPerovskite Origami for Programmable Microtube Lasing(Weinheim : Wiley-VCH, 2021) Dong, Haiyun; Saggau, Christian Niclaas; Zhu, Minshen; Liang, Jie; Duan, Shengkai; Wang, Xiaoyu; Tang, Hongmei; Yin, Yin; Wang, Xiaoxia; Wang, Jiawei; Zhang, Chunhuan; Zhao, Yong Sheng; Ma, Libo; Schmidt, Oliver G.Metal halide perovskites are promising materials for optoelectronic and photonic applications ranging from photovoltaics to laser devices. However, current perovskite devices are constrained to simple low-dimensional structures suffering from limited design freedom and holding up performance improvement and functionality upgrades. Here, a micro-origami technique is developed to program 3D perovskite microarchitectures toward a new type of microcavity laser. The design flexibility in 3D supports not only outstanding laser performance such as low threshold, tunable output, and high stability but also yields new functionalities like 3D confined mode lasing and directional emission in, for example, laser “array-in-array” systems. The results represent a significant step forward toward programmable microarchitectures that take perovskite optoelectronics and photonics into the 3D era. © 2021 The Authors. Advanced Functional Materials published by Wiley-VCH GmbH.
- ItemFast-Response Micro-Phototransistor Based on MoS2/Organic Molecule Heterojunction(Basel : MDPI, 2023) Andleeb, Shaista; Wang, Xiaoyu; Dong, Haiyun; Valligatla, Sreeramulu; Saggau, Christian Niclaas; Ma, Libo; Schmidt, Oliver G.; Zhu, FengOver the past years, molybdenum disulfide (MoS2) has been the most extensively studied two-dimensional (2D) semiconductormaterial. With unique electrical and optical properties, 2DMoS2 is considered to be a promising candidate for future nanoscale electronic and optoelectronic devices. However, charge trapping leads to a persistent photoconductance (PPC), hindering its use for optoelectronic applications. To overcome these drawbacks and improve the optoelectronic performance, organic semiconductors (OSCs) are selected to passivate surface defects, tune the optical characteristics, and modify the doping polarity of 2D MoS2. Here, we demonstrate a fast photoresponse in multilayer (ML) MoS2 by addressing a heterojunction interface with vanadylphthalocyanine (VOPc) molecules. The MoS2/VOPc van der Waals interaction that has been established encourages the PPC effect in MoS2 by rapidly segregating photo-generated holes, which move away from the traps of MoS2 toward the VOPc molecules. The MoS2/VOPc phototransistor exhibits a fast photo response of less than 15 ms for decay and rise, which is enhanced by 3ordersof magnitude in comparison to that of a pristine MoS2-based phototransistor (seconds to tens of seconds). This work offers a means to realize high-performance transition metal dichalcogenide (TMD)-based photodetection with a fast response speed.
- ItemImperceptible Supercapacitors with High Area-Specific Capacitance(Weinheim : Wiley-VCH, 2021) Ge, Jin; Zhu, Minshen; Eisner, Eric; Yin, Yin; Dong, Haiyun; Karnaushenko, Dmitriy D.; Karnaushenko, Daniil; Zhu, Feng; Ma, Libo; Schmidt, Oliver G.Imperceptible electronics will make next-generation healthcare and biomedical systems thinner, lighter, and more flexible. While other components are thoroughly investigated, imperceptible energy storage devices lag behind because the decrease of thickness impairs the area-specific energy density. Imperceptible supercapacitors with high area-specific capacitance based on reduced graphene oxide/polyaniline (RGO/PANI) composite electrodes and polyvinyl alcohol (PVA)/H2SO4 gel electrolyte are reported. Two strategies to realize a supercapacitor with a total device thickness of 5 µm—including substrate, electrode, and electrolyte—and an area-specific capacitance of 36 mF cm−2 simultaneously are implemented. First, the void volume of the RGO/PANI electrodes through mechanical compression is reduced, which decreases the thickness by 83% while retaining 89% of the capacitance. Second, the PVA-to-H2SO4 mass ratio is decreased to 1:4.5, which improves the ion conductivity by 5000% compared to the commonly used PVA/H2SO4 gel. Both advantages enable a 2 µm-thick gel electrolyte for planar interdigital supercapacitors. The impressive electromechanical stability of the imperceptible supercapacitors by wrinkling the substrate to produce folds with radii of 6 µm or less is demonstrated. The supercapacitors will be meaningful energy storage modules for future self-powered imperceptible electronics.