Inkjet printed electrochemical organic electronics

A conventional desktop inkjet printer has been used as a combined deposition and patterning tool of electrochemical organic transistors on rough flexible carriers. The functionality of these devices rely upon redox reactions occurring at the interface between a conjugated polymer film and an electrolyte. Both the electrolyte and the conjugated polymer suspension (an aqueous dispersion of poly(3,4-ethylenedioxythiophene):poly(styrene sulphonic acid)) were additively patterned with the inkjet printer, making the electrochemical device all-inkjet printed. Basic implementations of the transistor in simple electrochemical logical circuitry have been produced. The printing technique can be anticipated to be used for the production of small series of devices based on the electrochemical technology discussed.     

Paper-based, printed zinc–air battery

A flexible battery is printed on paper by screen-printing a zinc/carbon/polymer composite anode on one side of the sheet, polymerising a poly(3,4-ethylenedioxythiophene) (PEDOT) cathode on the other side of the sheet, and applying a lithium chloride electrolyte between the two electrodes. The PEDOT cathode is prepared by inkjet printing a pattern of iron(III)p-toluenesulfonate as a solution in butan-1-ol onto paper, followed by vapour phase polymerisation of the monomer. The electrolyte is prepared as a solution of lithium chloride and lithium hydroxide and also applied by inkjet printing on to paper, where it is absorbed into the sheet cross-section. Measurements on a zinc/carbon-PEDOT/air battery in a similar configuration on a polyethylene naphthalate substrate shows a discharge capacity of up to 1.4 mAh cm⁻² for an initial load of 2.5 mg zinc, equivalent to almost 70% of the zinc content of the anode, which generates 0.8 V at a discharge current of 500 μA. By comparison, the performance of the paper-based battery is lower, with an open-circuit voltage of about 1.2 V and a discharge capacity of 0.5 mAh cm². It appears that the paper/electrolyte combination has a limited ability to take up anode oxidation products before suffering a reduction in ionic mobility. The effects of different zinc/carbon/binder combinations, differences in application method for the zinc/carbon composite and various electrolyte compositions are discussed.     

Poly(3,4-ethylenedioxythiophene) nanospheres synthesized in magnetic ionic liquid

The synthesis of poly(3,4-ethylenedioxythiophene) nanospheres with their size ranging around 60 nm has been achieved by simply adding monomers into a magnetic ionic liquid, bmim[FeCl₄]. The ionic liquid leads to the formation of uniform nanospheres with a relatively narrow size distribution confined to submicrometer-sized domains. The polymers produced in this magnetic ionic liquid system are compared to those synthesized in conventional solution and emulsion polymerizations.     

喷墨印刷沉积的PEDOT/PSS薄膜导电性能

利用压电喷墨印刷技术沉积了PEDOT/PSS有机导电薄膜,研究了退火温度和乙二醇掺杂对薄膜导电性能的影响。实验结果表明:未退火和退火温度为120,140,160℃时,薄膜表面平均粗糙度分别为8.15,4.10,3.36,2.66nm;乙二醇掺杂使导电激活能由未掺杂时的0.096eV减小为0.046eV;电导激活能减小表明PEDOT分子链从低电导率的卷曲构象向高电导率的伸展构象转变;此外,乙二醇掺杂促使PSS与PE-DOT/PSS分离,使团聚的PEDOT/PSS颗粒变小从而分散更均匀,降低了表面粗糙度。     

Highly Customizable All Solution–Processed Polymer Light Emitting Diodes with Inkjet Printed Ag and Transfer Printed Conductive Polymer Electrodes

Inkjet and transfer printing processes are combined to easily form patterned poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) films as top anodes of all solution–processed inverted polymer light emitting diodes (PLEDs) on rigid glass and flexible plastic substrates. An adhesive PEDOT:PSS ink is formulated and fully customizable patterns are obtained using the inkjet printing process. In order to transfer the patterned PEDOT:PSS films, adhesion properties at interfaces during multistep transfer printing processes are carefully adjusted. The transferred PEDOT:PSS film on the plastic substrates shows not only a sheet resistance of 260.6 Ω/□ and a transmittance of 92.1% at 550 nm wavelength but also excellent mechanical flexibility. The PLEDs with spin‐coated functional layers sandwiched between the transferred PEDOT:PSS top anodes and inkjet‐printed Ag bottom cathodes are fabricated. The fabricated PLEDs on the plastic substrates show a high current efficiency of 10.4 cd A^?1 and high mechanical stability. It is noted that because both Ag and PEDOT:PSS electrodes can be patterned with a high degree of freedom via the inkjet printing process, highly customizable PLEDs with various pattern sizes and shapes are demonstrated on the glass and plastic substrates. Finally, with all solution process, a 5 × 7 passive matrix PLED array is demonstrated.     

Development of a simple method for fabrication of transparent conductive films with high mechanical strength

We have developed a simple method of fabricating transparent conductive films with a high mechanical strength on glass and indium tin oxide substrates. It does not require a large excess of organic solvents and polymerization catalysts and can yield smooth films by spin-coating of a mixture of a commercially available aqueous dispersion of poly(3,4-ethylenedioxythiophene)-poly(4-styrene sulfonate) and a neat liquid of tetraethyl orthosilicate. Preparation conditions such as feed ratio, kinds of additives, and annealing temperature and time were optimized to give highly conductive, transparent and mechanically strong films.     

Improvement of organic solar cell efficiency by solution-processed doping of pentacene in PEDOT:PSS layer

In the current research, organic solar cells (OSCs) with various concentrations of pentacene in Poly(ethylenedioxythiopene):Poly(styrenesulfonate) (PEDOT:PSS) interface layer were investigated for better hole extraction. The ITO/Pentacene?+?PEDOT:PSS/P3HT:PCBM/Al-fabricated solar cell fabricated via brush coating provides superior photovoltaic, electrical and optical characteristics when compared with the ITO/PEDOT:PSS/P3HT:PCBM/Al solar cell. The ITO/Pentacene?+?PEDOT:PSS/P3HT:PCBM/Al solar cells deliver a V_OC ~350?mV and 2.57% efficiency. It is observed that the optimized concentration of pentacene doping in PEDOT:PSS layer, along with an active layer of P3HT and PC₆₀BM, doubles the efficiency of the device, when compared with pristine PEDOT:PSS layer. The degradation studies of the fabricated bulk heterojunction OSCs reveal that the degrading abilities of ITO/Pentacene?+?PEDOT:PSS/P3HT:PCBM/Al solar cells are 60% more better than those of ITO/PEDOT:PSS/P3HT:PCBM/Al devices. Thus, this work will ultimately contribute toward fully solution processed painted device, which will provide low-cost manufacturing and improved stability of pentacene-based organic photovoltaics.     

Highly Stretchable and Sensitive Flexible Strain Sensor Based on Fe NWs/Graphene/PEDOT:PSS with a Porous Structure

With the rapid development of wearable smart electronic products, high-performance wearable flexible strain sensors are urgently needed. In this paper, a flexible strain sensor device with Fe NWs/Graphene/PEDOT:PSS material added under a porous structure was designed and prepared. The effects of adding different sensing materials and a different number of dips with PEDOT:PSS on the device performance were investigated. The experiments show that the flexible strain sensor obtained by using Fe NWs, graphene, and PEDOT:PSS composite is dipped in polyurethane foam once and vacuum dried in turn with a local linearity of 98.8%, and the device was stable up to 3500 times at 80% strain. The high linearity and good stability are based on the three-dimensional network structure of polyurethane foam, combined with the excellent electrical conductivity of Fe NWs, the bridging and passivation effects of graphene, and the stabilization effect of PEDOT:PSS, which force the graphene-coated Fe NWs to adhere to the porous skeleton under the action of PEDOT:PSS to form a stable three-dimensional conductive network. Flexible strain sensor devices can be applied to smart robots and other fields and show broad application prospects in intelligent wearable devices.     

Microstructure Engineering of Stretchable Resistive Strain Sensors with Discrimination Capabilities in Transverse and Longitudinal Directions

Featuring simple device structure, high sensitivity, and excellent reliability, stretchable resistive sensors have developed rapidly due to the high demand for flexible and wearable electronics. Nevertheless, it remains critically challenging to evaluate external stimuli using one simple device for diverse application scenarios. Here, a microstructure is engineered for a stretchable sensor by a facile replication/transferring and a prestretching/releasing process, enabling the device to have discrimination capabilities in the transverse direction (X-axis) and longitudinal direction (Y-axis). Consisting of silver nanowires (Ag NWs)/transition metal carbides (MXene)/poly(3,4-ethylenedioxythiophene):poly (styrene-sulfonate) (PEDOT:PSS) conducting layer and polydimethylsiloxane (PDMS)/Ecoflex elastomer, the microstructured sensor has a broad strain range of 120% along the X-axis and a large gauge factor (GF) of 37.44 along the Y-axis, and shows good stability during 1000 stretching/releasing cycles along two directions, indicating the excellent interfacial connection between the sensing layer and elastomer. As a result, taking advantages of distinct performance along two directions, the proposed stretchable sensor is demonstrated to monitor a variety of human movements and physical stimuli as a wearable and flexible device, revealing its promising potential in diverse application scenarios.     

Solvent treatment inducing ultralong cycle stability poly(3,4-ethylenedioxythiophene):poly(styrenesulfonic acid) fibers as binding-free electrodes for supercapacitors

As one kind of conducting polymer composite, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonic acid) (PEDOT:PSS) has been widely used as an electrode for energy storage and conversion devices because of its optical transmittance, flexibility, and high electrical conductivity etc. Here, we prepared binding-free PEDOT:PSS fibers (PFs) electrodes with high capacitive performance for supercapacitors via a facile method followed by various solvent treatments. Dimethyl sulfoxide (DMSO)-treated electrodes displayed a better specific capacitance (C_s) of 202 F/g at 0.5 A/g with higher elongation at break, flexibility, and conductivity of 140.7 S/cm, compared to those of pristine PEDOT:PSS materials. More importantly, the DMSO-treated fibers possessed improved stability, which retained 105% of the initial C_s after 22 000 long cycles at 10 A/g. It is believed that the fabricated PFs will be promising organic electrodes for portable supercapacitors and other flexible electronic devices in the near future.