In the past few decades, great attention has been paid to the development of IV–VI semiconductor colloidal quantum dots, such as PbSe, PbS and PbSSe, in infrared (IR) photodetectors due to their high photosensitivity, solution-processing and low cost fabrication. IR photodetectors based on field-effect transistors (FETs) showed high detectivity since the transconductance can magnify the drain–source current under certain applied gate voltages. However, traditional lateral FETs usually suffer from low photosensitivity and slow responsivity, which restricts their widespread commercial applications. In this work, therefore, novel vertical FET (VFET) based photodetectors are presented, in which the active layer is sandwiched between porous source electrode and planar drain electrode, resulting to ultrashort channel length. In this way, enhanced photoresponsivity and specific detectivity of 291 A W ⁻¹ and 1.84 × 10 ¹⁴ Jones, respectively, can be obtained at low drain–source voltage ( V _DS ) of −1 V and gate voltage ( V _g ) of −2 V under 100 μ W cm ⁻² illumination intensity, which was better than that of the traditional lateral FET based photodetectors. Therefore, it is promising to fabricate broadband photodetectors with high performance and good stability by this easy approach.

Recently, great attention has been paid to IV–VI colloidal quantum dots (CQDs) for their high photosensitivity, solution processability and low cost. Also, metal halide perovskites are very promising materials to realize the high-performance solution-processed visible-light photodetectors due to their cost-effective manufacturing, tunable absorption and photoluminescence in whole visible spectrum. In this paper, we present solution-processed CQDs-based tandem broadband photodetectors with low dark-current and high-sensitivity by inserting dielectric Polymethyl methacrylate (PMMA) interlayer between two sub-detectors. Our experimental data showed that the tandem broadband photodetector ITO/PEDOT:PSS/CsPbBr ₃ :PbS _0.4 Se _0.6 /ZnO/PVK/CsPbBr ₃ :PbS _0.4 Se _0.6 /ZnO/Au showed a maximum specific detectivity of 6.8 × 10 ¹³ Jones with a responsivity of 27 A W ⁻¹ under 57.8 μ W cm ⁻² 980 nm illumination. The device performance can be further enhanced by inserting a 50 nm dielectric PMMA layer between the two sub-photodetectors. As the result, the tandem photodetector ITO/PEDOT:PSS/CsPbBr ₃ :PbS _0.4 Se _0.6 /ZnO/PMMA(50 nm)/PVK/CsPbBr ₃ :PbS _0.4 Se _0.6 /ZnO/Au exhibits a maximum specific detectivity of 1.32 × 10 ¹⁴ Jones with a responsivity of 27.72 A W ⁻¹ under 57.8 μ W cm ⁻² of 980 nm laser. Further, the physical mechanisms for the enhanced performance are discussed in detail.

Implanted devices have important applications in biomedical monitoring, diagnosis and treatment, where intra-body communication (IBC) has a decent prospect in wireless implant communication technology by using the conductive properties of the human body to transmit a signal. Most of the investigations on implant IBC are focused on galvanic coupling type. Capacitive coupling IBC device seems hard to implant, because the ground electrode of it seemingly has to be exposed to air. Zhang et al. previously proposed an implantable capacitive coupling electrode, which can be totally implanted into the human body [1], but it lacks an overall characteristic investigation. In this paper, a comparable investigation of characteristics for implant intra-body communication based on galvanic and capacitive coupling is conducted. The human arm models are established by finite element method. Meanwhile, aiming to improve the accuracy of the model, electrode polarization impedance (EPI) is incorporated into the model, and the influences of electrode polarization impedance on simulation results are also analyzed. Subsequently, the corresponding measurements using porcine are conducted. We confirm good capacitive coupling communication performances can be achieved. Moreover, some important conclusions have been included by contrastive analysis, which can be used to optimize implant intra-body communication devices performance and provide some hints for practical IBC design. The conclusions also indicate that the implant IBC has promising prospect in healthcare and other related fields.

Wireless power transfer (WPT) is a crucial enabler for the long-term powering of existing implantable medical devices (IMDs). This article proposes a new design and analysis methodology for a tunable metasurface (MTS) based near-field magnetic WPT system. A near-field magnetic WPT system using a multi-coil topology creates stable power with a low specific absorption rate. However, maintaining the optimal performance of a system under misalignment conditions continues to be a challenging issue. To address this issue, the proposed design method enables the optimal coupling of the WPT system by tuning the system capacitances at a fixed frequency. Moreover, it is undefined to accurately determine the effective permeability of the MTS in the near-field range. Therefore, based on optimized results, a method is proposed to retrieve effective permeability in near-field scenarios. The effective permeability results are distinct from the typical response of the Lorentz oscillator. As a result, the specific connection between the optimization method and retrieval of effective permeability has been established. The methodology is applied to an exemplified system, where the maximal simulated and measured power transfer efficiencies at an implant depth of 8 cm are 2.32% and 2.60%, respectively. In addition, the planar MTS exhibits a high lateral misalignment tolerance, thereby enabling the development of a reliable WPT system for continuous power supply to IMDs.