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Poly (3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is widely used to build optoelectronic devices. However, as a hygroscopic waterbased acidic material, it brings major concerns for stability and degradation, resulting in an intense effort to replace it in organic photovoltaic (OPV) devices. In this work, we focus on the perfluorinated ionomer (PFI) polymeric additive to PEDOT:PSS. We demonstrate that it can reduce the relative amplitude of OPV device burn-in, and find two distinct regimes of influence. At low concentrations there is a subtle effect on wetting and work function, for instance, with a detrimental impact on the device characteristics, and above a threshold it changes the electronic and device properties. The abrupt threshold in the conducting polymer occurs for PFI concentrations greater than or equal to the PSS concentration and was revealed by monitoring variations in transmission, topography, work-function, wettability and OPV device characteristics. Below this PFI concentration threshold, the power conversion efficiency (PCE) of OPVs based on poly(3-hexylthiophene-2,5-diyl):[6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PCBM) are impaired largely by low fill-factors due to poor charge extraction. Above the PFI concentration threshold, we recover the PCE before it is improved beyond the pristine PEDOT:PSS layer based OPV devices. Supplementary to the performance enhancement, PFI improves OPV device stability and lifetime. Our degradation study leads to the conclusion that PFI prevents water from diffusing to and from the hygrosopic PEDOT:PSS layer, which slows down the deterioration of the PEDOT:PSS layer and the aluminum electrode. These findings reveal mechanisms and opportunities that should be taken into consideration when developing components to inhibit OPV degradation. 35-38 whilst oxidation, delamination and interfacial effects may occur at the electrodes. 39-45 Metal ion diffusion from the electrodes and changes in morphology have also been reported in both the active and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) layers. C. T. Howells et al. 2/14organic optoelectronics between indium tin oxide (ITO) anodes and active layers. [54][55][56][57] With its metal properties, 58-62 PEDOT:PSS and similar conducting layers are part of the contact and are sometimes called hole injection layers in light emitting devices. By analogy, in this solar cell work, PEDOT:PSS is then referred to as a hole extraction layer (HEL) rather than a hole transport layer or interlayer. The large ionisation potential promotes an Ohmic contact and improves the built-in electric field, whilst high conductivity and transparency ensure minimal resistive and optical losses, respectively. 53,63,64 The HEL also helps to prevent metal ion diffusion from the ITO into the active layer and the cathode from short-circuiting the anode. 50 The PSS is a water-soluble polyelectrolyte that serves as a charge balancing dopant during the polymerisation of EDOT monomers. It oxidises and stabi...

This study investigates the resistive switching (RS) behavior of Ag/HfO 2 (3 nm-thick)/SiO x (interfacial-layer)/Si devices. The findings are drawn from a systematic electrical and material characterization of the fabricated devices. Based on the current-time (I-t) and current-voltage (I-V) measurements, it is inferred that both metal and oxygen ion migration play a significant role in the switching events, leading to bipolar and unipolar switching modes depending on the biasing scheme. The results demonstrate two competing switching mechanisms taking place when the biasing voltage is increased beyond the RESET voltage in the bipolar mode. The devices are also shown to exhibit self-rectifying characteristics when the bias is applied to the Ag electrode. The proposed method of investigating the total charge passed through the device within the time to SET, during the I-t characterization, is particularly useful for identifying the current transport models governing the high-resistance state. The results reported in this manuscript provide useful insights into the control of RS behavior in this scientifically and technologically important material system. Developing a thorough understanding of the fundamental physics governing the observed RS behavior is a substantial step for the growing progress in the memristor device research, as well as for its potential exploitation in diverse CMOS-compatible applications.

This paper presents a deep learning-driven portable, accurate, low-cost, and easy-to-use device to perform Reverse-Transcription Loop-Mediated Isothermal Amplification (RT-LAMP) to facilitate rapid detection of COVID-19. The 3D-printed device—powered using only a 5 Volt AC-DC adapter—can perform 16 simultaneous RT-LAMP reactions and can be used multiple times. Moreover, the experimental protocol is devised to obviate the need for separate, expensive equipment for RNA extraction in addition to eliminating sample evaporation. The entire process from sample preparation to the qualitative assessment of the LAMP amplification takes only 45 min (10 min for pre-heating and 35 min for RT-LAMP reactions). The completion of the amplification reaction yields a fuchsia color for the negative samples and either a yellow or orange color for the positive samples, based on a pH indicator dye. The device is coupled with a novel deep learning system that automatically analyzes the amplification results and pays attention to the pH indicator dye to screen the COVID-19 subjects. The proposed device has been rigorously tested on 250 RT-LAMP clinical samples, where it achieved an overall specificity and sensitivity of 0.9666 and 0.9722, respectively with a recall of 0.9892 for Ct < 30. Also, the proposed system can be widely used as an accurate, sensitive, rapid, and portable tool to detect COVID–19 in settings where access to a lab is difficult, or the results are urgently required.

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