Tissue-Electronics Interfaces

Tissue-electronics interfaces provide a two-way communication between biological tissue and external electronics devices to record electrophysiological signals and stimulation of the living organs. This Chapter presents an overview of significant progresses in tissue-electronics interfaces. At first, we evaluate principal properties of the living tissue microenvironment important for tissue-specific equipment design. Next, we study charge transfer mechanisms in the biological tissues, bulk electrode materials, and tissue-electronics interfaces. After that, we highlight the current developing and promising advanced biomaterials for the neural electrodes, significantly leading to the development of bionanoelectronics and bionic organs. Finally, the challenges and future outlook of the neural interfaces will be discussed

Low‐Temperature Processing Methods for Tin Oxide as Electron Transporting Layer in Scalable Perovskite Solar Cells

Perovskite solar cell (PSC) technology experiences a remarkably rapid growth toward commercialization with certified efficiency of over 25%, along with the outstanding breakthrough in the development of SnO2. Owing to the wide bandgap, high electron mobility, chemical stability, and low photocatalytic activity, SnO2 has been the rising star to serve as electron transporting layer (ETL). More importantly, the low-temperature fabrication process (<200 °C) enables SnO2 a promising candidate for the industry, making it compatible with the plastic substrates and large-scale production, which is crucial for the flexible and scalable devices fabrication. In this review, the processing methods (solution-based, vacuum-based, and vapor-based deposition) of low-temperature SnO2 (LT-SnO2) and the pros and cons of them with a focus on their scalability are discussed. Additionally, the morphologies of obtained LT-SnO2 are investigated to guide the design and performance improvement of devices. The modification strategies to reduce undesired nonradiative recombination and passivate the defects in the bulk or at the interface of LT-SnO2, influencing the quality of perovskite films, together with the efficiency and stability of cells are summarized. This review is a comprehensive overview of the studies on low-temperature SnO2 ETL and provides detailed instructions for scalable PSCs

When photoluminescence, electroluminescence, and open-circuit voltage diverge : light soaking and halide segregation in perovskite solar cells

Perovskite solar cells suffer from various instabilities on all time scales. Some of them are driven by light, in particular when employing compounds with mixed halides. Such light soaking effects have been observed in performance changes of solar-cell devices. They have also been spectroscopically investigated in detail on films, where the formation of a low-gap iodine rich phase, seen in a red shift of the PL has been made responsible for a reduced open-circuit voltage. However, studies synchronously examining device performance and its relation to spectroscopy data, are scarce. Here, we perform an in-operandum study, where we investigate changes of open-circuit voltage (Voc) and photocurrent during light soaking and complement it with photo- (PL) and electroluminescence (EL) data on devices, which allow analysis of the Voc-limiting processes using optical and optoelectronic reciprocity relations. We find that changes in the Voc for stable single halide compositions are quantitatively correlated with changes in the PL intensity, showing that the Voc follows changes in the quasi-Fermi level splitting. In contrast, changes in Voc for the mixed halide composition are not correlated to the emergence of the low-gap phase, confirming that this phase is not the sole culprit for a low and instable Voc. Instead, non-radiative voltage losses influenced by mobile ions are dominant in devices containing compositions with high Br content. Interestingly, the low-gap phase contributes less to photocurrent, as seen by a wavelength-dependent PL quenching at short circuit. This observation might be explained by the formation of emissive but partially insulated iodine-rich regions in the film. Such an effect is also possible for single halide systems, when the perovskite composition is not stable, seen in an increase of PL at short circuit during light soaking. This indicates that ion migration in general causes photovoltaically inactive regions, without enhancing non-radiative recombination. EL measurements confirm that Rau’s reciprocity relation between external EL quantum efficiency and Voc cannot readily be applied to absorbers with such different phases.Perovskite solar cells suffer from various instabilities on all time scales. Some of them are driven by light, in particular when employing compounds with mixed halides. Such light soaking effects have been observed in performance changes of solar-cell devices. They have also been spectroscopically investigated in detail on films, where the formation of a low-gap iodine rich phase, seen in a red shift of the PL has been made responsible for a reduced open-circuit voltage. However, studies synchronously examining device performance and its relation to spectroscopy data, are scarce. Here, we perform an in-operandum study, where we investigate changes of open-circuit voltage (Voc) and photocurrent during light soaking and complement it with photo- (PL) and electroluminescence (EL) data on devices, which allow analysis of the Voc-limiting processes using optical and optoelectronic reciprocity relations. We find that changes in the Voc for stable single halide compositions are quantitatively correlated with changes in the PL intensity, showing that the Voc follows changes in the quasi-Fermi level splitting. In contrast, changes in Voc for the mixed halide composition are not correlated to the emergence of the low-gap phase, confirming that this phase is not the sole culprit for a low and instable Voc. Instead, non-radiative voltage losses influenced by mobile ions are dominant in devices containing compositions with high Br content. Interestingly, the low-gap phase contributes less to photocurrent, as seen by a wavelength-dependent PL quenching at short circuit. This observation might be explained by the formation of emissive but partially insulated iodine-rich regions in the film. Such an effect is also possible for single halide systems, when the perovskite composition is not stable, seen in an increase of PL at short circuit during light soaking. This indicates that ion migration in general causes photovoltaically inactive regions, without enhancing non-radiative recombination. EL measurements confirm that Rau’s reciprocity relation between external EL quantum efficiency and Voc cannot readily be applied to absorbers with such different phases

Comparison of Trap-state Distribution and Carrier Transport in Nanotubular and Nanoparticulate TiO2 Electrodes for Dye-Sensitized Solar Cells

Dye-sensitized solar cells (DSCs) with nanotubular TiO2 electrodes of varying thicknesses are compared to DSCs based on conventional nanoparticulate electrodes. Despite the higher degree of order in one-dimensional nanotubular electrodes, electron transport times and diffusion coeffs., detd. under short-circuit conditions, are comparable to those of nanoparticulate electrodes. The quasi-Fermi level, however, is much lower in the nanotubes, suggesting a lower concn. of conduction band electrons. This provides evidence for a much higher diffusion coeff. for conduction band electrons in nanotubes than in nanoparticulate films. The electron lifetime and the diffusion length are significantly longer in nanotubular TiO2 electrodes than in nanoparticulate films. Nanotubular electrodes have a trap distribution that differs significantly from nanoparticulate electrodes; they possess relatively deeper traps and have a characteristic energy of the exponential distribution that is more than two times that of nanoparticulate electrodes

Enhancing air filtration efficiency with triboelectric nanogenerators in face masks and industrial filters

The removal efficiency of traditional air filters decreases with decreasing particle size, requiring the use of highly compact filter layers to achieve high efficiency, resulting in high-pressure drops and power consumption. To address this issue, this study proposes a novel approach by combining triboelectric nanogenerator (TENG) properties with industrial air filters and face masks to improve removal efficiency while maintaining low-pressure drop. The study investigates the impacts of key parameters, such as airflow velocity, particle size, and applied voltage, on filter performance through a developed mathematical model. The optimal voltage range required to remove specific particle sizes is also modeled, and suitable triboelectric materials for producing the optimal voltage are suggested. Results show that the use of the suggested triboelectric-based filter, generated using a polypropylene (PP)-polyurethane (PU) TENG pair, with a 300 \ub5m filter thickness, 30 \ub5m pore size, and 30 \ub5m fiber diameter, enhances the removal efficiency of particles from 23.0 % to 99.0 %. Specifically, a 10 V voltage on the fiber surface enables the removal of particles in the range of 10 nm to 100 \ub5m with an efficiency of 99.0 %, which is 4 times higher than a traditional filter. The study demonstrates the potential of utilizing various antibacterial and polymer-based triboelectric materials in different applications, including self-powered smart face masks and industrial air filters

Investigation on the dynamics of electron transport and recombination in TiO2 nanotube/nanoparticle composite electrodes for dye-sensitized solar cells

In this work, the fabrication and characterization are reported of dye-sensitized solar cells based on TiO2 nanotube/nanoparticle (NT/NP) composite electrodes. TiO2 nanotubes were prepd. by anodization of Ti foil in an org. electrolyte. The nanotubes were chem. sepd. from the foil, ground and added to a TiO2 nanoparticle paste, from which composite NT/NP electrodes were fabricated. In the composite TiO2 films the nanotubes existed in bundles with a length of a few micrometers. By optimizing the amt. of NT in the paste, dye-sensitized solar cells with an efficiency of 5.6% were obtained, a 10% improvement in comparison to solar cells with pure NP electrodes. By increasing the fraction of NT in the electrode the c.d. increased by 20% (from 11.1-13.3 mA cm-2), but the open circuit voltage decreased from 0.78-0.73 V. Electron transport, lifetime and extn. studies were performed to investigate this behavior. A higher fraction of NT in the paste led to more and deeper traps in the resulting composite electrodes. Nevertheless, faster electron transport under short-circuit conditions was found with increased NT content, but the electron lifetime was not improved. The electron diffusion length calcd. for short-circuit conditions was increased 3-fold in composite electrodes with an optimized NT fraction. The charge collection efficiency was more than 90% over a wide range of light intensities, leading to improved solar cell performance

Origin of apparent light-enhanced and negative capacitance in perovskite solar cells

So-called negative capacitance seems to remain an obscure feature in the analysis of the frequency-dependent impedance of perovskite solar cells. It belongs to one of the puzzling peculiarities arising from the mixed ionic-electronic conductivity of this class of semiconductor. Here we show that apparently high capacitances in general (positive and negative) are not related to any capacitive feature in the sense of a corresponding charge accumulation. Instead, they are a natural consequence of slow transients mainly in forward current of the diode upon ion displacement when changing voltage. The transient current leads to a positive or negative 'capacitance' dependent on the sign of its gradient. The 'capacitance' appears so large because the associated resistance, when thinking of a resistor-capacitor element, results from another physical process, namely modified electronic charge injection and transport. Observable for a variety of devices, it is a rather universal phenomenon related to the hysteresis in the current-voltage curve