Triboelectric nanogenerators (TENGs) offer an emerging market of self-sufficient power sources, converting the mechanical energy of the environment to electricity. Recently reported high power densities for the TENGs provide new applications opportunities, such as self-powered sensors. Here in this research, a flexible graphene oxide (GO) paper was fabricated through a straightforward method and utilized as the electrode of TENGs. Outstanding power density as high as 1.3 W.m⁻², an open-circuit voltage up to 870 V, and a current density of 1.4 µA.cm⁻² has been extracted in vertical contact-separation mode. The all-flexible TENG has been employed as a self-powered humidity sensor to investigate the effect of raising humidity on the output voltage and current by applying mechanical agitation in two forms of using a tapping device and finger tapping. Due to the presence of superficial functional groups on the GO paper, water molecules are inclined to be adsorbed, resulting in a considerable reduction in both generated voltage (from 144 V to 14 V) and current (from 23 µA to 3.7 µA) within the range of relative humidity of 20% to 99%. These results provide a promising applicability of the first suggested sensitive self-powered GO TENG humidity sensor in portable/wearable electronics.

Recently, organic–inorganic perovskites have manifested great capacity to enhance the performance of photovoltaic systems, owing to their impressive optical and electronic properties. In this simulation survey, we employed the Solar Cell Capacitance Simulator (SCAPS-1D) to numerically analyze the effect of different hole transport layers (HTLs) (Spiro, CIS, and CsSnI₃) and perovskite active layers (ALs) (FAPbI₃, MAPbI₃, and CsPbI₃) on the solar cells’ performance with an assumed configuration of FTO/SnO₂/AL/HTL/Au. The influence of layer thickness, doping density, and defect density was studied. Then, we trained a machine learning (ML) model to perform predictions on the performance metrics of the solar cells. According to the SCAPS results, CsSnI₃ (as HTL) with a thickness of 220 nm, a defect density of 5 × 10¹⁷ cm⁻³, and a doping density of 5 × 10¹⁹ cm⁻³ yielded the highest power conversion efficiency (PCE) of 23.90%. In addition, a 530 nm-FAPbI₃ AL with a bandgap energy of 1.51 eV and a defect density of 10¹⁴ cm⁻³ was more favorable than MAPbI₃ (1.55 eV) and CsPbI₃ (1.73 eV) to attain a PCE of >24%. ML predicted the performance matrices of the investigated solar cells with ~75% accuracy. Therefore, the FTO/SnO₂/FAPbI₃/CsSnI₃/Au structure would be suitable for experimental studies to fabricate high-performance photovoltaic devices.

Carbon nanotubes (CNTs) coatings have been shown over the past few years as a promising material for neural interface applications. In particular, in the field of nerve implants, CNTs have fundamental advantages due to their unique mechanical and electrical properties. In this study, carbon nanotubes multi-electrode arrays (CNT-modified-Au MEAs) were fabricated based on gold multi-electrode arrays (Au-MEAs). The electrochemical impedance spectra of CNT-modified-Au MEA and Au-MEA were compared employing equivalent circuit models. In comparison with Au-MEA (17 Ω), CNT-modified-Au MEA (8 Ω) lowered the overall impedance of the electrode at 1 kHz by 50%. The results showed that CNT-modified-Au MEAs have good properties such as low impedance, high stability and durability, as well as scratch resistance, which makes them appropriate for long-term application in neural interfaces.

In this research, we employed transient photo-voltage rise and decay measurements to investigate the origin of slow unsymmetrical rise and decay profiles in single and triple cation perovskite solar cells. Drastic changes in photo-voltage decay profile were observed upon insertion of Br⁻, Cs⁺ and FA⁺ ions into perovskite structures. In order to explain our observations, the activation energy for ionic defects was measured and an equivalent circuit model was proposed containing both electrical and ionic components. The electrical branch consists of a diode, the bulk capacitance and resistances for charge transport and recombination. In parallel we introduced an ionic branch describing the ionic response by a resistance for ionic charge transport and a capacitance describing ion accumulation at the interface to the charge transport layer. To reproduce the asymmetry of photo-voltage rise and decay, a diode with a parallel resistor is introduced leading to a belayed backflow of the accumulated ions. The results revealed that the activation energy of ionic defects became larger upon insertion of either halides or cations. There is larger amount of ionic defects in the case of MAPbI₃ while the de-accumulation process of ions happens in much larger time scale in triple cation perovskite. The presence of ions at the interfaces results in band bending generating a potential barrier restraining electrons and holes from recombination; so the loss of built-in potential is delayed until de-accumulation of ionic double layer happens. Our model proposes that the loss of built-in potential depends on electrostatic potential drop, suggesting coupled electronic-ionic phenomenon in perovskite solar cells.