Highly Conductive and Transparent PEDOT:PSS Films with a Fluorosurfactant for Stretchable and Flexible Transparent Electrodes

Highly conductive and transparent poly‐(3,4‐ethylenedioxythiophene):poly(styrenesulfonic acid) (PEDOT:PSS) films, incorporating a fluorosurfactant as an additive, have been prepared for stretchable and transparent electrodes. The fluorosurfactant‐treated PEDOT:PSS films show a 35% improvement in sheet resistance (R_s) compared to untreated films. In addition, the fluorosurfactant renders PEDOT:PSS solutions amenable for deposition on hydrophobic surfaces, including pre‐deposited, annealed films of PEDOT:PSS (enabling the deposition of thick, highly conductive, multilayer films) and stretchable poly(dimethylsiloxane) (PDMS) substrates (enabling stretchable electronics). Four‐layer PEDOT:PSS films have an R_s of 46 Ω per square with 82% transmittance (at 550 nm). These films, deposited on a pre‐strained PDMS substrate and buckled, are shown to be reversibly stretchable, with no change to R_s, during the course of over 5000 cycles of 0 to 10% strain. Using the multilayer PEDOT:PSS films as anodes, indium tin oxide (ITO)‐free organic photovoltaics are prepared and shown to have power conversion efficiencies comparable to that of devices with ITO as the anode. These results show that these highly conductive PEDOT:PSS films can not only be used as transparent electrodes in novel devices (where ITO cannot be used), such as stretchable OPVs, but also have the potential to replace ITO in conventional devices.     

PEDOT:PSS/Ketjenblack Holey Nanosheets with Ultrahigh Areal Capacitance for kHz AC Line-Filtering Micro-Supercapacitors

Supercapacitors, with their superior capacity and lower space occupancy, offer inherent advantages over aluminum electrolytic capacitors (AECs) in meeting the demands of miniaturization and planarization of devices. However, the capacitive advantage of supercapacitors is often compromised by the limited availability of electrode materials under high-frequency alternating current conditions. The development of electrode materials that possess both high-frequency response and high capacity is undoubtedly critical. Herein, PEDOT:PSS/Ketjenblack holey nanosheets (PKHNs) prepared by a solvent thermal method are successfully developed as the electrode material to ensure rapid ion transport and abundant charge storage on the accessible nanosheet surfaces. The micro-supercapacitors exhibit a high-frequency capacitance (3089 µF cm⁻² at 120 Hz, with a phase angle of −81.9°), achieved through an innovative structural design utilizing PKHNs materials. These micro-supercapacitors demonstrate excellent frequency response with efficient 120 Hz filtering and offer volumetric advantages over the state-of-the-art commercial ones during low-voltage operations, making them an ideal choice for the next-generation miniaturized filter capacitors.     

Stretchable and Transparent Conductive PEDOT:PSS‐Based Electrodes for Organic Photovoltaics and Strain Sensors Applications

The development of transparent, conducting, and stretchable poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)‐based electrodes using a combination of a polyethylene oxide (PEO) polymer network and the surfactant Zonyl is reported. The latter improves the ductility of PEDOT:PSS and enables its deposition on hydrophobic surfaces such as polydimethylsiloxane (PDMS) elastomers, while the presence of a 3D matrix offers high electrical conductivity, elasticity, and mechanical recoverability. The resulting electrode exhibits attractive properties such as high electrical conductivity of up to 1230 S cm^?1 while maintaining high transparency of 95% at 550 nm. The potential of the electrode technology is demonstrated in indium‐tin‐oxide (ITO)‐free solar cells using the PBDB‐T‐2F:IT‐4F blend with a power conversion efficiency of 12.5%. The impact of repeated stretch‐and‐release cycles on the electrical resistance is also examined in the effort to evaluate the properties of the electrodes. The interpenetrated morphology of the PEDOT:PSS and polyethylene oxide network is found to exhibit beneficial synergetic effects resulting in excellent mechanical stretchability and high electrical conductivity. By carefully tuning the amount of additives, the ability to detect small changes in electrical resistance as a function of mechanical deformation is demonstrated, which enables the demonstration of stretchable and resilient on‐skin strain sensors capable of detecting small motions of the finger.     

Doping and Design of Flexible Transparent Electrodes for High-Performance Flexible Organic Solar Cells: Recent Advances and Perspectives

Substantial effort has been devoted to both chemical doping and design of flexible transparent electrodes (FTEs) for flexible organic solar cells (OSCs) in the past decade. Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate), graphene, metal nanostructures, metal oxide/ultrathin metal/metal oxide, Mxene, and their hybrid electrodes emerge to be the most promising flexible conducting materials over indium tin oxide. The FTE fabrications play a critical role in flexible OSCs. This feature review article summarizes the current status on the researches of the FTEs including various approaches and strategies to boost the conductivity, work function, mechanical flexibility, wettability, etc, which directly affect the performances of the flexible OSCs. The most cutting edge progresses on both FTEs and flexible OSCs are highlighted along the line. Advantages and plausible issues are pointed out. Perspectives are provided that can advance the developments of the flexible OSCs. This review raises the awareness for the importance of developing plenty of FTEs and reveals their critical role in flexible OSCs.     

High‐Performance Ultrathin Flexible Solid‐State Supercapacitors Based on Solution Processable Mo1.33C MXene and PEDOT:PSS

MXenes, a young family of 2D transition metal carbides/nitrides, show great potential in electrochemical energy storage applications. Herein, a high performance ultrathin flexible solid‐state supercapacitor is demonstrated based on a Mo_1.33C MXene with vacancy ordering in an aligned layer structure MXene/poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonic acid) (PEDOT:PSS) composite film posttreated with concentrated H₂SO₄. The flexible solid‐state supercapacitor delivers a maximum capacitance of 568 F cm^?3, an ultrahigh energy density of 33.2 mWh cm^?3 and a power density of 19 470 mW cm^?3. The Mo_1.33C MXene/PEDOT:PSS composite film shows a reduction in resistance upon H₂SO₄ treatment, a higher capacitance (1310 F cm^?3) and improved rate capabilities than both pristine Mo_1.33C MXene and the nontreated Mo_1.33C/PEDOT:PSS composite films. The enhanced capacitance and stability are attributed to the synergistic effect of increased interlayer spacing between Mo_1.33C MXene layers due to insertion of conductive PEDOT, and surface redox processes of the PEDOT and the MXene.     

A Wrinkled PEDOT:PSS Film Based Stretchable and Transparent Triboelectric Nanogenerator for Wearable Energy Harvesters and Active Motion Sensors

The functionalized conductive polymer is a promising choice for flexible triboelectric nanogenerators (TENGs) for harvesting human motion energy still poses challenges. In this work, a transparent and stretchable wrinkled poly(3,4‐ethylenedioxythiophene):poly(4‐styrenesulfonate) (PEDOT:PSS) electrode based TENG (WP‐TENG) is fabricated. The optimum conductivity and transparency of PEDOT:PSS electrode can reach 0.14 kΩ □⁻¹ and 90%, respectively, with maximum strain of ≈100%. Operating in single‐electrode mode at 2.5 Hz, the WP‐TENG with an area of 6 × 3 cm² produces an open‐circuit voltage of 180 V, short‐circuit current of 22.6 µA, and average power density of 4.06 mW m⁻². It can be worn on the wrist to harvest hand tapping energy and charge the capacitor to 2 V in ≈3.5 min, and then drive an electronic watch. Furthermore, the WP‐TENG as the human motion monitoring sensor could inspect the bending angle of the elbow and joint by analyzing the peak value of voltage and monitor the motion frequency by counting the peak number. The triboelectric mechanism also enables the WP‐TENG to realize high‐performance active tactile sensing. The assembled 3 pixel × 3 pixel tactile sensor array is fabricated for mapping the touch location or recording the shape of object contacted with the sensor array.     

Hybrid photovoltaic structures based on amorphous silicon and P3HT:PCBM/PEDOT:PSS polymer semiconductors

Hybrid thin film photovoltaic structures, based on hydrogenated silicon (Si:H), organic poly(3-hexythiophene):methano-fullerenephenyl-C61-butyric-acid-methyl-ester (P3HT:PCBM) and poly(3,4ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) films, have been fabricated. Organic semiconductor thin films were deposited by spin-coating technique and were exposed to radio frequency plasma enhanced chemical vapor deposition (RF PECVD) of Si:H films at deposition temperature T_d = 160 °C. Different types of structures have been investigated: H1) ITO/(p)SiC:H /P3HT:PCBM/(n) Si:H, H2) ITO/PEDOT:PSS/(i)Si:H/(n) Si:H and H3) ITO/PEDOT:PSS/P3HT:PCBM/(i)Si:H/(n)Si:H. Short circuit current density spectral response and current-voltage characteristics were measured for diagnostic of the photovoltaic performance. The current density spectral dependence of hybrid structures which contains organic layers showed improved response (50–80%) in high photon energy range (hν ≈ 3.1–3.5 eV) in comparison with Si:H reference structure. An adjustment in the absorbing layer thickness and in the contact material for ITO/PEDOT:PSS/(i)Si:H/(n)Si:H structure, resulted in a remarkably high short circuit current density (as large as 17.74 mA/cm²), an open circuit voltage of 640 mV and an efficiency of 3.75%.