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Wearable bio-sensing devices are considered promising for ubiquitous heath monitoring. To accurately read out small bio-signals, the development of high-performance flexible front-end circuits is crucial. Oxide semiconductors are considered one of the most promising active channel materials for on-polymeric-foil electronics. In this article, a high-gain flexible complementary metal–oxide–semiconductor (CMOS) inverter with a beta ratio of 1, a desirable feature for device miniaturization, was demonstrated by monolithically integrating a top-gated n-type indium gallium zinc oxide (IGZO) thin-film transistor (TFT) and a bottom-gated p-type SnO TFT on a 5.5- $\mu \text{m}$ -thick polyimide substrate. The influence of atomic layer deposited (ALD)-HfO2 capping layer on the properties of oxide active channels has been analyzed. The flexible inverter exhibited a high static voltage gain of 370 V/V and balanced noise margins (noise margin high of 4.8 V, noise margin low of 4.7 V) for a supply voltage of 10 V. In addition, the voltage transfer characteristics remained virtually unchanged when the device was subjected to an outward or an inward bending radius of 2.5 mm, indicating the complementary oxide-TFT-based inverter is practical for flexible electronics applications.

Reduced graphene oxide (rGO)-SnO2 nanocomposites are fabricated on carbon cloth from screen-printed pastes containing rGO nanoflakes and SnCl2 liquid precursor by using a nitrogen atmospheric-pressure plasma jet (APPJ). RGO-SnO2-coated carbon cloth is then used as the electrode of gel-electrolyte supercapacitors (SCs). Experiments conducted with various APPJ processing times suggest that the optimal APPJ processing time is 300 s. Cyclic voltammetry (CV) measurements indicate that 300-s APPJ processing results in the best areal capacitance of 97.53 mF/cm2. The capacitance retention rate is ~85% after a 10,000-cycle CV test. Further, capacitance increases by 11% after a 1000-cycle bending test under a bending radius of 7.5 mm, possibly owing to the better electrolyte/electrode contact and decrease in the charge transport resistance after mechanical bending. This study also characterized APPJ-processed rGO-SnO2 nanocomposites by scanning electron microscopy with energy dispersive spectroscopy, X-ray photoelectron spectroscopy, X-ray diffractometry, Raman spectroscopy, and water contact angle measurements.

This study demonstrates a method for patterning paper-based microfluidic devices. An octadecyltrichlorosilane (OTS) solution is used to coat a chromatography paper to make it hydrophobic. A low-temperature (~ 32.9 °C) atmospheric-pressure dielectric-barrier-discharge jet with a shadow mask is then used to pattern hydrophilic stripes on the OTS-coated hydrophobic paper. In this manner, 1-mm-wide hydrophilic stripes are patterned successfully. Liquids are demonstrated to be transported and mixed in the hydrophilic stripes. Water contact angle measurement, X-ray photoelectron spectroscopy, surface profiler, optical emission spectroscopy, and scanning electron microscopy are used to characterize effect of pattering.

LiCl + Mn(NO3)2·4H2O pastes are screen-printed on a carbon cloth substrate and then calcined at 400 °C for 6 h in a tube furnace to convert them into LiMn2O4. Ar, Ar+5%H2, or Ar+5%O2 low-pressure plasma is then used to treat the LiMn2O4/carbon cloth. The treated LiMn2O4/carbon cloth is then used as the electrode for a Li-ion hybrid supercapacitors (Li-HSCs) with a three-electrode configuration in 1-M Li2SO4 liquid electrolyte. Ag/AgCl and Pt electrodes were used as reference and counter electrodes, respectively. Li-HSCs are characterized by galvanostatic charging/discharging, cyclic voltammetry, and electrochemical impedance spectroscopy. The results indicate that plasma treatment improves the Li-HSCs performance. In particular, Ar+5%O2 plasma treatment increases the areal capacity by ∼24% to 23.12 μA h cm−2. It also improves the coulomb efficiency and capacity retention rate of LiMn2O4 Li-HSCs.

This study investigates the effect of low-pressure plasma (LPP) processing of a graphite foil as the cathode of a paper-based fluidic Al-air battery. A 10-s plasma treated battery exhibited better discharge performance in terms of the current density, power density, and energy density compared with an untreated battery. Scanning electron microscopy, x-ray photoelectron spectroscopy, and water contact angle measurements were used to investigate the difference in the surface properties of the graphite foil before and after LPP modification. Further, linear sweep voltammetry, constant current discharge measurement, and electrochemical impedance spectroscopy analysis were used to demonstrate the enhancement in discharge performance.

This study fabricated temperature sensors with a mixture of carbon nanotube (CNT) and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). CNT/PEDOT:PSS solutions with three different ratios—1/5, 1/9, and 1/13—prepared and aged for 0, 3, and 6 days. The temperature sensor was fabricated by drop-casting the aged solution onto a flexible polydimethylsiloxane (PDMS) substrate. As the aging time of CNT/PEDOT:PSS solutions with ratios of 1/5, 1/9, and 1/13 increased to 6 days, the temperature coefficient of resistance (TCR) of CNT/PEDOT:PSS decreased from −1.97, −1.99, and −2.15 (%/°C) to −2.80, −2.61, and −2.51 (%/°C) (i.e. temperature sensitivity increased) and temperature index (TI) also increased from 2242.5, 2249.1, and 2503.8 (K) to 3530.1, 3085.7, and 3002.5 (K), respectively. As the aging time of CNT/PEDOT:PSS solution increased to 6 days, its Seebeck coefficient increased from 52.4 to 114.5 μV K−1. These results show that the aging of CNT/PEDOT:PSS solution significantly increased the temperature sensitivity and Seebeck coefficient via the dedoping of PEDOT:PSS. This serves as a facile method to improve the temperature sensitivity of the CNT/PEDOT:PSS composite.

Reduced graphene oxide (rGO)-polyaniline (PANI) supercapacitors (SCs) are tested with 1 M LiCl, Li2SO4, and H2SO4 electrolytes. The SC performance is evaluated by electrical impedance spectroscopy, cyclic voltammetry (CV), and galvanostatic charging/discharging measurements. Electrochemical experiments indicate that rGO-PANI SCs with lithium salt electrolytes show a large pseudocapacitance (PC) effect whereas that with H2SO4 electrolyte shows a large electrical double-layer capacitance (EDLC) effect. The rGO-PANI SC with H2SO4 electrolyte has the largest areal capacitance of 48.83 mF/cm2, whereas those with LiCl and Li2SO4 electrolytes have the areal capacitances of 31.69 mF/cm2 and 22.35 mF/cm2, respectively. After a 10,000-cycle CV stability test, the rGO-PANI SC with Li2SO4 electrolyte shows some ion embedding, resulting in better cycling stability than those of SCs with LiCl and H2SO4 electrolytes.

Reduced graphene oxide (rGO) and/or polypyrrole (PPy) are mixed with chitosan (CS) binder materials for screen-printing supercapacitors (SCs) on arc atmospheric-pressure plasma jet (APPJ)-treated carbon cloth. The performance of gel-electrolyte rGO/CS, PPy/CS, and rGO/PPy/CS SCs processed by a dielectric barrier discharge plasma jet (DBDjet) was assessed and compared. DBDjet processing improved the hydrophilicity of these three nanocomposite electrode materials. Electrochemical measurements including electrical impedance spectroscopy (EIS), cyclic voltammetry (CV), and galvanostatic charging-discharging (GCD) were used to evaluate the performance of the three types of SCs. The Trasatti method was used to evaluate the electric-double layer capacitance (EDLC) and pseudocapacitance (PC) of the capacitance. The energy and power density of the three types of SCs were illustrated and compared using Ragone plots. Our experiments verify that, with the same weight of active materials, the combined use of rGO and PPy in SCs can significantly increase the capacitance and improve the operation stability.

A nitrogen DC-pulse atmospheric-pressure plasma jet (APPJ) is used to convert spin-coated nickel acetate liquid precursor films into continuous and dense NiO compound thin films. Films calcined by APPJ for 0–120 s are characterized. X-ray photoelectron spectroscopy (XPS) indicates that metallic Ni content increases and then decreases as the APPJ calcination time increases. Wrinkles are formed on films with higher metallic Ni contents owing to the compressive stresses caused by the mismatch between the film and the substrate. Plasma reactive species contain electrons and ions that could cause oxidation and reduction reactions simultaneously. This leads to the complex compositions in the resultant films. The film becomes more metal-like when the metallic Ni content is high and becomes more semiconductor-like for low metallic Ni content film. Seebeck measurements confirms that all APPJ-converted NiO compound films are of p-type and could potentially be used as the hole transport layer or the hole injection layer of optoelectronic devices.

A low-temperature (

The effect of atmospheric-pressure dielectric barrier discharge (DBD) treatment on the properties of methylammonium lead iodide (CH3NH3PbI3, MAPbI3) perovskite thin films is investigated. The in-situ DBD-treated MAPbI3 perovskite thin films are then used as the absorber layers for planar n-i-p perovskite solar cells (PSCs). N-O emission system is observed in the plasma during the treatment, indicating the reactions of reactive nitrogen plasma species with the organics in the precursor films. Long DBD treatment duration (60 s) leads to the phase precipitation of PbI2 and degrades the cell efficiency, whereas short DBD treatment duration (20 s) significantly improves the PSC efficiency by nearly 40%. Only slight performance enhancement is observed in the PSCs prepared by conventional thermal treatment at the same substrate temperatures as that for DBD treatment, implying that DBD provides the synergetic effect of the reactivity and plasma heating. Electrochemical impedance spectroscopy (EIS) indicates that the charge recombination impedance increases and then decreases with DBD treatment duration. The shunt resistance also shows a similar trend, and it is consistent with the PSC performance. The PSC with the 20 s DBD-treated absorber layer shows energy conversion efficiency of 14.29%, open circuit voltage of 1.022 V, short circuit current density of 19.45 mA/cm2, and fill factor of 0.72, whereas the corresponding values for the untreated counterpart are 10.32%, 0.976 V, 18.52 mA/cm2, and 0.57. The result shows that short-duration low-temperature DBD treatment effectively enhances the performance of solution-processed PSCs.

We compare screen-printed flexible reduced graphene oxide(rGO)-chitosan(CS) supercapacitors (SCs) prepared using poly(3, 4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) pastes and carbon pastes (CPs). SCs with PEDOT:PSS (PEDOT:PSS/rGO-CS SCs) exhibit a higher pseudocapacitance (PC) than do those with CP. Plasma treatment damages the electrodes and lowers the specific capacitance of SCs. In a galvanostatic charge-discharge (GCD) test with a constant current of 0.25 mA, PEDOT:PSS/rGO-CS and CP/rGO-CS SCs respectively show a maximum specific capacitance of 14.70 mF cm−2 and 4.63 mF cm−2. PEDOT:PSS/rGO-CS and CP/rGO-CS SCs both show excellent performance in the stability and bending tests. With a 5,000-cycle cyclic voltammetry (CV) test, the capacitive retention rates are more than 97%. No degradation is observed for both PEDOT:PSS/rGO-CS and CP/rGO-CS SCs bent with a bending radius of 0.5 cm.

In an all-vanadium redox flow battery (VRFB), redox reaction occurs on the fiber surface of the graphite felts. Therefore, the VRFB performance highly depends on the characteristics of the graphite felts. Although atmospheric pressure plasma jets (APPJs) have been applied for surface modification of graphite felt electrode in VRFBs for the enhancement of electrochemical reactivity, the influence of APPJ plasma reactivity and working temperature (by changing the flow rate) on the VRFB performance is still unknown. In this work, the performance of the graphite felts with different APPJ plasma reactivity and working temperatures, changed by varying the flow rates (the conditions are denoted as APPJ temperatures hereafter), was analyzed and compared with those treated with sulfuric acid. X-ray photoelectron spectroscopy (XPS) indicated that the APPJ treatment led to an increase in O-/N-containing functional groups on the GF surface to ~21.0% as compared to ~15.0% for untreated GF and 18.0% for H2SO4-treated GF. Scanning electron microscopy (SEM) indicated that the surface morphology of graphite felt electrodes was still smooth, and no visible changes were detected after oxidation in the sulfuric acid or after APPJ treatment. The polarization measurements indicated that the APPJ treatment increased the limiting current densities from 0.56 A·cm−2 for the GFs treated by H2SO4 to 0.64, 0.68, and 0.64 A·cm−2, respectively, for the GFs APPJ-treated at 450, 550, and 650 °C, as well as reduced the activation overpotential when compared with the H2SO4-treated electrode. The electrochemical charge/discharge measurements showed that the APPJ treatment temperature of 550 °C gave the highest energy efficiency of 83.5% as compared to 72.0% with the H2SO4 treatment.

Pastes containing reduced graphene oxide (rGO) and SnCl2 solution were screen printed on carbon cloth and then calcined using a CO2 tornado-type atmospheric-pressure plasma jet (APPJ). The tornado circulation of the plasma gas enhances the mixing of the reactive plasma species and thus ensures better reaction uniformity. Scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS) were performed to characterize the synthesized rGO-SnO2 nanocomposites on carbon cloth. After CO2 tornado-type APPJ treatment, the pastes were converted into rGO-SnO2 nanocomposites for use as the active electrode materials of polyvinyl alcohol (PVA)-H2SO4 gel-electrolyte flexible supercapacitors (SCs). Various APPJ scanning times were tested to obtain SCs with optimized performance. With seven APPJ scans, the SC achieved the best areal capacitance of 37.17 mF/cm2 in Galvanostatic charging/discharging (GCD) and a capacitance retention rate of 84.2% after 10,000-cycle cyclic voltammetry (CV) tests. The capacitance contribution ratio, calculated as pseudocapacitance/electrical double layer capacitance (PC/EDLC), is ~50/50 as analyzed by the Trasatti method. GCD data were also analyzed to obtain Ragone plots; these indicated an energy density comparable to those of SCs processed using a fixed-point nitrogen APPJ in our previous study.

Two-dimensional perovskite solar cells (2-D PSCs) have attracted much research attention in recent years because they are more stable in a regular environment than three-dimensional (3-D) ones are. In this study, we doped Cs into 2D perovskite (BA2(MA)2Pb3I10) films as the absorbing layers of the 2-D p-i-n inverted PSCs to investigate the influence of the Cs doping concentration on the properties of the 2-D perovskite films and the fabricated solar cells. Cs doping clearly improves the power conversion efficiency (PCE) and air stability of the PSCs. Doping perovskite with 10% Cs (the best doping concentration in this study) can increase the PSC efficiency from 7.98% to 10.11%. Scanning electron microscopy indicates the improved surface quality and crystallinity by Cs doping. However, excess Cs doping degrades the PCE of the PSCs. Furthermore, 10% Cs doped PSCs show air stability superior to that of undoped ones in unpackaged humidity environments. After exposure to 55% relative humidity (RH) in 19 °C air for 300 h, the PCE of the PSC decreased by only 39%, in contrast to 84% for the undoped PSC.

We use a poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)/carbon nanotube (CNT) composite as the temperature sensing layer, and the device exhibited a high sensitivity of −2.46%/°C. A sandpaper-molded PDMS with fluorinated surface modification protection layer is used as the superhydrophobic, oleophobic, self-cleaning protective encapsulation layer. This device exhibits a self-cleaning function when it makes contact with liquids such as water, tea, coffee, and milk. In addition, the surface can also repel liquids with low surface tension (such as oil), exhibiting good oleophobicity. Resistance to ultrasonication in an organic solvent for 120 min and a 400-cycle tape peel test reveal durability of this device. The device functions under similar conditions after 1000 bending cycles with a bending radius of 0.875 mm. In this work, we demonstrate a simple and low-cost technique to fabricate durable and wearable temperature sensing devices.

In this study, flexible and low-cost graphite sheets modified by atmospheric pressure plasma jet are applied to reduced-graphene-oxide/polyaniline supercapacitors. Surface treatment by atmospheric pressure plasma jet can make the hydrophobic surface of graphite into a hydrophilic surface and improve the adhesion of the screen-printed reduced-graphene-oxide/polyaniline on the graphite sheets. After the fabrication of reduced-graphene-oxide/polyaniline supercapacitors with polyvinyl alcohol/H2SO4 gel electrolyte, pseudo-capacitance and electrical double capacitance can be clearly identified by the measurement of cyclic voltammetry. The fabricated supercapacitor exhibits specific capacitance value of 227.32 F/g and areal capacitance value of 28.37 mF/cm2 with a potential scan rate of 2 mV/s. Meanwhile, the capacitance retention rate can reach 86.9% after 1000-cycle cyclic voltammetry test. A light-emitting diode can be lit by the fabricated reduced-graphene-oxide/polyaniline supercapacitors, which confirms that the supercapacitors function well and can potentially be used in a circuit.

A facile surface treatment of the CH3NH3PbI3 film is conducted using a portable dielectric barrier discharge device inside a nitrogen-filled glove box. DBD treatment can promote the surface crystallization of the CH3NH3PbI3 film, increase the conductivity of CH3NH3PbI3 film, and manifest efficient defect passivation. In addition, DBD treatment can remove surface N-containing fragments of perovskite film to produce a lead-rich surface, which not only affords self-passivation effect but also increases the interactions at the perovskite/fullerene interface. Benefitting from the reduced defect density at the perovskite interface, the DBD-treated perovskite film can enable a ∼12.5% enhancement in power conversion efficiency of the derived doped PC61BM-based perovskite solar cells. Such enhancement is mainly contributed from the improvement of open circuit voltage (from 0.885 to 0.922 V) and fill factor (0.698 to 0.759). Detailed optimization of the DBD treatment is carefully investigated in this study.

Surface condition and corrosion resistance are major concerns when metallic materials are going to be utilized for applications. In this study, FeCoNiCr medium-entropy alloy (MEA) is first treated with a nitrogen atmospheric-pressure plasma jet (APPJ) and then coated with octadecyltrichlorosilane (OTS) for the surface modification. The hydrophobicity of the FeCoNiCr MEA was effectively improved by OTS-coating treatment, APPJ treatment, or the combination of both treatments (OTS-coated APPJ-treated), which increased the water contact angle from 54.49&deg, of the bare MEA to 70.56&deg, 93.94&deg, and 88.42&deg, respectively. Potentiodynamic polarization and electrochemical impedance spectroscopy tests demonstrate that the APPJ-treated FeCoNiCr MEA exhibits the best anti-corrosion properties. X-ray photoelectron spectroscopy reveals that APPJ treatment at 700 &deg, C oxidizes all the alloying elements in the FeCoNiCr MEA, which demonstrates that a short APPJ treatment of two-minute is effective in forming a metal oxide layer on the surface to improve the corrosion resistance of FeCoNiCr MEA. These results provide a convenient and rapid method for improving surface properties of FeCoNiCr MEA.

In this paper, low-pressure 95%Ar–5%H2, pure Ar, and 95%Ar–5%O2 plasmas were used for post-treatment of ruthenium (Ru) deposited on nickel foam (NF) (Ru/NF). Ru/NF was then tested as a catalyst for a hydrogen evolution reaction. Significant improvement in electrocatalytic activity with the lowest overpotential and Tafel slope was observed in an alkaline electrolyte (1 M KOH) with 95%Ar–5%O2 plasma processing on Ru/NF. Linear scanning electrical impedance spectroscopy (EIS) and cyclic voltammetry (CV) also indicate the lowest interfacial impedance and largest electrical double layer capacitance. Experimental results with 0.1 M phosphate buffered saline (PBS) and 0.5 M H2SO4 electrolytes were also demonstrated and compared.

This study compares supercapacitors with reduced graphene oxide (rGO)‑carbon black (CB) and CB nanocomposite coated carbon cloth electrodes. We use a nitrogen DC-pulse atmospheric pressure plasma jet (APPJ) to process the electrodes. The APPJ processing time is

Nitrogen dc-pulse atmospheric pressure plasma jet (APPJ) is used to fabricate Pt/ZnO composites as the counter electrodes (CEs) of dye-sensitized solar cells (DSSCs). Due to the synergetic effect of the reactive plasma species and heat in nitrogen APPJ, the spin-coated precursors including chloroplatinic acid and zinc acetate can be reduced on fluorine-doped tin oxide (FTO) glass substrates in a few seconds. X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) analyses indicate that the precursors are reduced to Pt/ZnO under APPJ calcination. Electrochemical impedance spectroscopy (EIS) and Tafel measurement show the promising catalytic activities of Pt/ZnO CEs with low charge transfer resistance and high exchange current density. The efficiency of a DSSC with a 30-s APPJ-calcined Pt/ZnO CE is similar to that with a conventional furnace-annealed Pt CE for 15 min. The results indicate that nitrogen dc-pulse APPJ treatment is an efficient tool for rapidly fabricating Pt/ZnO composite CEs of DSSCs.

This study evaluates carbon cloth treated using dc-pulse nitrogen atmospheric pressure plasma jet (APPJ) for a polyvinyl alcohol (PVA)/sulfuric acid (H2SO4) gel-electrolyte supercapacitor with a polyaniline (PANI)/reduced graphene oxide (rGO) nanocomposite electrode materials. The water contact angle of the carbon cloth decreases from 144.71° to 0° after the scanning APPJ surface treatment. The improved wettability can facilitate the penetration of the electrolyte into the porous electrodes, thereby improving the capacitance. X-ray photoelectron spectroscopy (XPS) indicates the introduction of nitrogen doping into to the carbon fibers of carbon cloth through the nitrogen APPJ treatment. Without APPJ treatment of carbon cloth, the specific (areal) capacitance of the fabricated supercapacitor is 315.0 F g−1 (55.67 mF/cm2); it increases to 580.2 F g−1 (106.89 mF/cm2) with APPJ surface treatment of carbon cloth before screen-printing the PANI/rGO nanocomposite. Electrochemical impedance spectroscopy (EIS) indicates a decreasing charge-transfer impedance at the electrode/electrolyte interface for supercapacitors with APPJ treatment of carbon cloth. This also improves the supercapacitive performance. After 1000-cycle cyclic voltammetry stability test, the capacitance retention rate is ∼85%. Our experimental results suggest that nitrogen dc-pulse APPJ in scanning mode is an efficient tool for enhancing the supercapacitance performance of a PANI/rGO supercapacitor.

This study evaluates DC-pulse nitrogen atmospheric-pressure-plasma-jet processed carbon nanotube (CNT)–reduced graphene oxide (rGO) nanocomposites for gel-electrolyte supercapacitor applications. X-ray photoelectron spectroscopy (XPS) indicates decreased oxygen content (mainly, C–O bonding content) after nitrogen APPJ processing owing to the oxidation and vaporization of ethyl cellulose. Nitrogen APPJ processing introduces nitrogen doping and improves the hydrophilicity of the CNT–rGO nanocomposites. Raman analysis indicates that nitrogen APPJ processing introduces defects and/or surface functional groups on the nanocomposites. The processed CNT–rGO nanocomposites on carbon cloth are applied to the electrodes of H2SO4–polyvinyl alcohol (PVA) gel-electrolyte supercapacitors. The best achieved specific (areal) capacitance is 93.1 F g−1 (9.1 mF cm−2) with 15 s APPJ-processed CNT–rGO nanocomposite electrodes, as evaluated by cyclic voltammetry under a potential scan rate of 2 mV s−1. The addition of rGOs in CNTs in the nanoporous electrodes improves the supercapacitor performance.

In this study, the easy-to-operate silver mirror reaction (SMR) was used for metallizing chromatography paper. The SMR-metallized paper was characterized by water contact angle measurements, a surface profiler, x-ray photoelectron spectroscopy, UV–Vis spectroscopy, x-ray diffraction, and electrical resistance measurement. The characterization results show that Ag was successfully synthesized on cellulose fibers and was electrically conductive after cyclic bending. Moreover, this SMR-metallized paper was used as electrodes for fabricating a supercapacitor. This SMR-metallized paper could be used for realizing cost-effective flexible electronics applied in on-site biochemical sensing in resource-limited settings.

East Asian calligraphy black ink (hereafter called simply “black ink”) is used to fabricate flexible conducting chromatography paper electrode by a simple and low-cost method. The black ink-coated paper was characterized by scanning electron microscopy, surface profiler, water contact angle measurement, electrical resistance measurement, X-ray photoelectron spectroscopy, and X-ray diffraction. The hydrophilicity slightly decreased after black ink coating but still provided good adhesion to the follow-up reduced graphene oxide/polyaniline/chitosan slurry coating for fabricating supercapacitor electrodes. A 1000-cycle repeated bending test with a bending radius of 5 mm revealed good conductance retention. Instrumental analyses indicated that the carbon black in the black ink was the main contributor to the electrical conductance. The supercapacitor with black-ink-coated paper electrodes exhibited an areal specific capacitance of up to 179.08 mF cm−2 and coulomb efficiency of 80%. This confirmed that the black-ink-coated paper electrode could be feasibly applied to a supercapacitor. This black-ink-coated paper can be easily fabricated in resource-limited settings, and it provides new possibilities for the use of paper-based electrodes in flexible electronics.

A bathocuproine (BCP) layer is typically used as the hole-blocking layer in p-i-n-structure perovskite solar cells (PSCs) between PC61BM and Ag electrodes. Before evaporating the Ag, we used a low-temperature (&lt, 40 °C) atmospheric-pressure dielectric barrier discharge jet (DBDjet) to treat the BCP with different scan rates. The main purpose of this was to change the contact resistance between the BCP layer and the Ag electrodes through surface modification using a DBDjet. The best power conversion efficiency (PCE) of 13.11% was achieved at a DBDjet scan rate of 2 cm/s. The He DBDjet treatment introduced nitrogen to form C-N bonds and create pits on the BCP layer. This deteriorated the interface between the BCP and the follow-up deposited-Ag top electrode. Compared to the device without the plasma treatment on the BCP layer, the He DBDjet treatment on the BCP layer reduced photocurrent hysteresis but deteriorated the fill factor and the efficiency of the PSCs.

We use a dc-pulse nitrogen atmospheric-pressure plasma jet (APPJ) to calcine carbon nanotubes (CNTs) pastes that are screen-printed on carbon cloth. 30-s APPJ treatment can efficiently oxidize and vaporize the organic binders, thereby forming porous structures. As indicated by X-ray photoelectron spectroscopy (XPS) and electron probe microanalysis (EPMA), the oxygen content decreases after APPJ treatment owing to the oxidation and vaporization of ethyl cellulose, terpineol, and ethanol. Nitrogen doping was introduced to the materials by the nitrogen APPJ. APPJ-calcination improves the wettability of the CNTs printed on carbon cloth, as evidenced by water contact angle measurement. Raman spectroscopy indicates that reactive species of nitrogen APPJ react violently with CNTs in only 30-s APPJ processing time and introduce defects and/or surface functional groups on CNTs. Carbon cloths with calcined CNT layers are used as electrodes for liquid and quasi-solid-state electrolyte supercapacitors. Under a cyclic voltammetry test with a 2 mV/s potential scan rate, the specific capacitance is 73.84 F/g (areal capacitance = 5.89 mF/cm2) with a 2 M KCl electrolyte and 66.47 F/g (areal capacitance = 6.10 mF/cm2) with a H2SO4/polyvinyl alcohol (PVA) gel electrolyte.