PSS Layer Research Articles

3D Charge Transport Pathway in Organic Solar Cells via Incorporation of Discotic Liquid Crystal Columns

In this work, a discotic liquid crystal (DLC) 2,3,6,7,10,11‐hexaacetoxytriphenylene (HATP) is used as the interlayer between poly(3,4‐ethylene‐dioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) and the active layer to achieve 3D charge transportation for organic solar cells (OSCs). HATP exhibits a columnar structure with a dominantly edge‐on orientation. For a (non‐)fullerene OSC system based on face‐on orientation, HATP columns are favorable for the expansion of edge‐on and face‐on crystallite in the active layer. According to the surface energy, surrounding the HATP columns are mainly acceptors. The significantly improved electron mobility indicates that it is easier for the electron to hop into HATP columns to transport, which represents the formation of the 3D pathway. This transport mode typically can enhance the intermolecular charge transport and effectively suppress the generation of triplet excitons and recombination. Thus, the short‐circuit current density (JSC) is increased by 14% and 19% for fullerene and non‐fullerene systems, respectively. The power conversion efficiency is improved for non‐fullerene OSCs with different active layer thicknesses (≥150 nm) and fullerene OSCs with an active layer thickness of 140 nm. Overall, this work demonstrates an approach to introduce HATP columns on a PEDOT:PSS layer that has great potential to form a 3D pathway for achieving high‐performance (non‐)fullerene OSCs.

Modification of interface between PEDOT:PSS and perovskite film inserting an ultrathin LiF layer for enhancing efficiency of perovskite light-emitting diodes

Abstract PEDOT:PSS has been widely used in perovskite light-emitting diodes (PeLEDs) due to its high hole current conductivity and work function. However, the unbalanced charge injection and severe exciton quenching in PEDOT:PSS restrict the EL performance of PeLEDs. In this work, a facile interface modification method is introduced in which an ultrathin LiF layer is inserted at the interface between PEDOT:PSS and MAPBBr3 perovskite film. Our results indicate that the inserted ultrathin LiF layer contributes to an efficient interface passivation effect between the PEDOT:PSS layer and the perovskite film, which significantly suppresses both the exciton quenching by the conductive PEDOT chains and the perovskite film defect density at the interface. Moreover, balanced charge injection is realized by adjusting the thickness of the LiF layer, which also serves as an electron blocking layer, in order to preferentially hinder electron current over hole current. Consequently, the optimal PeLED with a 2 nm LiF layer exhibits a significantly decreased turn-on voltage of 2.8 V compared to 4.9 V of the pristine device without a LiF layer, combined with an over 100-fold enhancement in the maximum luminance (10415 cd/m2), current efficiency (12.1 cd/A), and external quantum efficiency (3.5%).

A hybrid P3HT-Graphene interface for efficient photostimulation of neurons

Graphene conductive properties have been long exploited in the field of organic photovoltaics and optoelectronics by the scientific community worldwide. We engineered and characterized a hybrid biointerface in which graphene is coupled with photosensitive polymers, and tested its ability to elicit light-triggered neural activity modulation in primary neurons and blind retina explants. We designed such a graphene-based device by modifying a photoactive P3HT-based retinal interface, previously reported to rescue light sensitivity in blind rodents, with a CVD graphene layer replacing the conductive PEDOT:PSS layer to enhance charge separation. The new graphene-based device was characterized for its electrochemical features and for the ability to photostimulate primary neurons and blind retina explants, while preserving biocompatibility. Light-triggered responses, recorded by patch-clamp in vitro or MEA ex vivo, show a stronger light-transduction efficiency when the neurons are interfaced with the graphene-based device with respect to the PEDOT:PSS-based one. The possibility to ameliorate flexible photo-stimulating devices via the insertion of graphene, paves the way for potential biomedical applications of graphene-based neuronal interfaces in the context of retinal implants.

Economically Sustainable Growth of Perovskite Photovoltaics Manufacturing

Summary The significant capital expense of photovoltaics manufacturing has made it difficult for new cell and module technologies to enter the market. We present two technoeconomic models that analyze the sustainable growth of perovskite manufacturing for an R2R single-junction technology and a perovskite-silicon tandem module, focusing on the impacts of economies of scale and average selling price on profitability. We establish a cost range of $3.30/W to $0.53/W for flexible modules manufactured in factory sizes ranging from 0.3 MW/year to 1 GW/year. In addition, we model the cost to manufacture a tandem module consisting of a single-junction perovskite cell stacked in 4-terminal configuration onto a silicon cell and show how an existing manufacturer can grow at a faster rate by co-investing in tandems. Our analyses highlight potential routes to market for perovskite photovoltaics and the possibility to sustainably grow a photovoltaics manufacturing company even in markets with higher labor rates.

A new green‐to‐transmissive polymer with electroactive poly(3,4‐ethylene dioxythiophene):poly(styrene sulfonate) as an interface layer for achieving high‐performance electrochromic device

AbstractA new neutral green electrochromic (EC) polymer, namely poly(5,8‐bis(2,3‐dihydro[3,4‐B][1,4]dioxin‐5‐yl)‐2,3‐dual(4‐(hexadecyloxy) phenyl) quinoxaline) (PBOPEQ) was designed and synthesized. PBOPEQ‐poly(3,4‐ethylene dioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) film was further prepared by electrochemical polymerization on the PEDOT:PSS modified indium tin oxide (ITO) electrode. Scanning electron microscopy images and ultrasonic experiment indicate that PBOPEQ‐PEDOT:PSS film shows better film‐forming ability and stronger interface adhesive with ITO electrode compared to that of PBOPEQ film. It is worth mentioning that PBOPEQ‐PEDOT:PSS film presents more reversible redox characteristic, better optical contrast (~40%) and coloration efficiency (~230 cm2 C−1) at 678 nm, excellent EC stability and memory property (36 hr), which should be ascribed to that the electroactive PEDOT:PSS layer facilitates the charge transfer process and enhances the ion doping/dedoping properties. EC device based on PBOPEQ‐PEDOT:PSS film exhibits superior integrated performance such as reversible color change from green to transmissive, optical contrast of 41.0% and switching time less than 1 s. Accordingly, PBOPEQ‐PEDOT:PSS is an excellent EC material when combined with electroactive PEDOT:PSS interface layer for achieving high performance device, which shows potential applications in displays, electronic papers, and tags.

Stretchable and durable Parylene/PEDOT:PSS/Parylene multi-layer induced by plastic deformation for stretchable device using functionalized PDMS

Currently, electronic components having wavy structures are being actively studied because such wavy structures exhibit stretchability through flattening under stretching. The buckling of a thin film on an elastomer is an easy and inexpensive approach of creating a wavy structure and has attracted considerable attention. Despite its simplicity and easiness, the requirement of stretchers during film deposition limits fabrication methods, such as spin-coating and printing methods, and hinders their application in industry. Here, we eliminated the requirement of stretchers during film deposition by utilizing plastic deformation of the thin film and extending methods of developing a wrinkle structure. We used poly-3,4-ethylenedioxythiophene:polystyrene sulfonate (PEDOT:PSS), the most widely used conductive polymer, as a thin film and adopted its stretchable wrinkle structure for stretchable electronic devices. The stretchability and durability of PEDOT:PSS were enhanced by sandwiching the PEDOT:PSS layer between two Parylene layers. The PEDOT:PSS layer was conductive at a stretch of up to 170%, and the change in resistance was less than 10% after 4000 cyclic loads. Additionally, we demonstrated a new concept of a flexible and stretchable light emitting device using the proposed Parylene/PEDOT:PSS/Parylene multi-layer and functionalized polydimethylsiloxane.

Effect of the PEDOT:PSS buffer layer on the performance of hybrid ZnO nanorods/polymer electroluminescent diode

Hybrid ZnO nanorods/polymer light-emitting diodes have excited much attraction because of the combination of high optoelectronic properties of ZnO nanorod with the variety and processability of polymers. In this research, the hybrid ZnO nanorods/polymer heterostructure UV-LED is investigated using ATLAS module of SILVACO TCAD software. In order to observe the influence of PEDOT:PSS hole injection layer/buffer layer in a AZO/ZnO NRs/MEH-PPV heterostructure device, first an ab initio approach have been done on PEDOT:PSS, MEH-PPV and AZO layers. The density of states, electronic band structure and the imaginary part of the dielectric function have been analyzed to deduce the electronic and optic features of the aforesaid layers. In continue, current–voltage characteristics and electroluminescence (EL) spectra of three structures of ITO/MEH-PPV/Al, ITO/ZnO/MEH-PPV/Al and ITO/ZnO/ZnO NR/MEH-PPV/Al have been simulated and compared with the literature experimental works to verify the simulation approach. Moreover, Langevin recombination rate, radiative recombination rate and luminescence power of the mentioned structures have been carefully investigated. Finally, the current–voltage characteristics, luminescence power and EL spectra of the novel proposed devices with the structures of ITO/PEDOT:PSS/AZO/ZnO NR/MEH-PPV/Al and ITO/PEDOT:PSS/ZnO/ZnO NR/MEH-PPV/Al have been investigated. The turn-on voltage of the proposed structure is decreased from 22 to 16 V because of the insertion of the PEDOT:PSS buffer layer and lowering of the hole injection barrier between ITO and ZnO layers. A little blue shift is observed around the wavelength of 380 nm which is attributed to the AZO layer.

Improved Interfacial Crystallization by Synergic Effects of Precursor Solution Stoichiometry and Conjugated Polyelectrolyte Interlayer for High Open-Circuit Voltage of Perovskite Photovoltaic Diodes.

The open-circuit voltage (Voc) of perovskite photovoltaic diodes depends largely on the selection of charge transport layers (CTLs) and surface passivation, which makes it important to understand the physical processes occurring at the interface between the perovskite and a CTL. We provide a direct correlation between Voc and the interfacial characteristics of perovskites tuned through stoichiometry engineering of precursor solutions and surface modification of the underlying poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) layer. Poor quality interfacial perovskite crystals were observed on top of the PEDOT:PSS layer, resulting in strong interfacial recombination and a low Voc. In contrast, the growth of the interfacial perovskite crystals was significantly improved by the synergic effects of varying the precursor solution composition and covering the surface with a pH-neutral conjugated polyelectrolyte, poly[2,6-(4,4-bis(potassium butanylsulfonate)-4H-cyclopenta[2,1-b;3,4-b']dithiophene)-alt-4,7-(2,1,3-benzothiadiazole)] (CPE-K), which possesses potassium ions as counter ions. The influence of the energy-level alignment at the interface on Voc was also discussed. Our findings highlight that improved perovskite crystallization at the interface can facilitate bulk growth of perovskite grains in the vertical direction and effectively suppress nonradiative surface charge recombination, thus enhancing the short-circuit current and Voc.

Fabrication and Characterization of DSSC/Si Tandem Solar Cell with PEDOT:PSS/ITO Buffer Layer

In this study, dye-sensitized solar cell (DSSC)/silicon tandem solar cells were fabricated by changing the buffer layer structure. When joining two cells, a buffer layer is important to efficiently transport electrons by suppressing buffer of electrons by a potential barrier. Therefore, we used PEDOT:PSS/ITO as buffer layer structures, and measured their solar cell characteristics. As a result, it was found that the structure in which both PEDOT:PSS layer and ITO layer are stacked as buffer layers is suitable for the buffer layer of DSSC/Si tandem cells. In addition, the characteristics improved each time DMSO was added to PEDOT:PSS, and as a result, the characteristics of tandem solar cells also tended to improve. The maximum conversion efficiency (Voc = 0.78 V, Jsc = 4.87 mA / cm2, FF = 0.62, Eff = 2.35 %) was obtained when the DMSO concentration was 1%. It was suggested that conversion efficiency can be improved by improving the buffer layer.

Electrical properties of nitric acid and DMSO treated PEDOT:PSS/n‐Si hybrid heterostructures for optoelectronic applications

ABSTRACTOrganic/inorganic heterostructures are an emerging and interesting field of research for optoelectronics. In this work, an efficient organic/inorganic hybrid heterojunction between PEDOT:PSS and n‐type Silicon has been fabricated for optoelectronic applications. Samples with varying thickness of PEDOT:PSS were prepared by spin coating technique and the electrical conductivity of organic layers was modified using DMSO as additive. Post fabrication, the hybrid heterostructures were treated with HNO3 vapor so as to enhance the conductivity of the organic layer. Surface treatment with HNO3 was found to lower the roughness of the organic layer and enhance the transparency of the layer. I–V characteristics reveal optimized behavior of HNO3 treated PEDOT:PSS layer with a low Ideality factor (n~3.2) and a barrier height (ΦB) of 0.8 eV. The findings of the study provide a promising efficient method to enhance the electrical and device properties of PEDOT:PSS/n‐Si heterostructures for optoelectronic applications. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48952.

Small molecular material as an interfacial layer in hybrid inverted structure perovskite solar cells

Hybrid halide perovskites are becoming increasingly popular due to their immense potential to be used as a low cost and easily processable solar cell technology. Interfacial engineering is believed to be one of the crucial ways to improve the device performance. In this work, we report the introduction of a small molecular interfacial layer 4,4’-(naphthalene-2,6-diyl)bis(N,N-bis(4-methoxyphenyl)aniline) (TPA-NAP-TPA) between the traditional hole transporting layer poly (3,4-ethylenedioxythiophene:polystyrene sulfonate) (PEDOT:PSS) and perovskite (Cs0.15FA0.85PbI3) active layer. Systematic investigations indicate that the incorporation of the small molecular interfacial layer improves the inverted device efficiency by 7% relative. The crystallinity and morphology of the perovskite formed on top of the PEDOT:PSS/TPA-NAP-TPA is favourable compared to the perovskite formed on top of pristine PEDOT:PSS layer. The improvement in the PCE is attributed to increased photocurrent generation. The devices containing the interfacial layer has also depicted improved quantum yield which is in line with the maximised average JSC. Furthermore, the devices with PEDOT:PSS/TPA-NAP-TPA interfacial layer retained 60% of their initial efficiency after 30 days, which is 30% higher than the devices with pristine PEDOT:PSS layer. Including interfacial layers such as TPA-NAP-TPA could be a viable technique in order to enhance the performance and stability of inverted structure perovskite solar cells.

Simultaneously improving thermopower and electrical conductivity via polar organic solvents aided layer-by-layer technique

In recent years, organic/inorganic hybrids capture wide attention due to their advantages in endowing composites with both high Seebeck coefficient and low thermal conductivity originating from inorganics and polymer, respectively. However, simply blending tend to weaken this advantage, resulting in lower thermoelectric performance than that of single organics or inorganics. Here we propose a polar organic solvents aided layer-by-layer (OS-LbL) technique to prepare high performance nanocomposite films comprising poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) and Sb2Te3 nanocomposites. Polar organic solvents not only promote the dispersion of Sb2Te3 nanoplates but also post-treat the PEDOT:PSS layer at the hetero-junction interface, successfully increasing the electrical conductivity and thermopower at the same time. Besides, the organic/inorganic interface inducing by OS-LbL promotes a low thermal conductivity of 0.0522 Wm−1K−1. As a result, a maximum ZT value up to 0.10 at room temperature. The results show that using OS-LbL method to combine PEDOT:PSS with Sb2Te3 nanoplates is a promising pathway to achieve polymer-based, high-performance thermoelectric applications.

Acidity Suppression of Hole Transport Layer via Solution Reaction of Neutral PEDOT:PSS for Stable Perovskite Photovoltaics.

Poly(3,4-ethylenedioxythiophene): poly(4-styrenesulfonate) (PEDOT:PSS) is typically used for hole transport layers (HTLs), as it exhibits attractive mechanical, electrical properties, and easy processability. However, the intrinsically acidic property can degrade the crystallinity of perovskites, limiting the stability and efficiency of perovskite solar cells (PSCs). In this study, inverted CH3NH3PbI3 photovoltaic cells were fabricated with acidity suppressed HTL. We adjusted PEDOT:PSS via a solution reaction of acidic and neutral PEDOT:PSS. And we compared the various pH-controlled HTLs for PSCs devices. The smoothness of the pH-controlled PEDOT:PSS layer was similar to that of acidic PEDOT:PSS-based devices. These layers induced favorable crystallinity of perovskite compared with acidic PEDOT:PSS layers. Furthermore, the enhanced stability of pH optimized PEDOT:PSS-based devices, including the prevention of degradation by a strong acid, allowed the device to retain its power conversion efficiency (PCE) value by maintaining 80% of PCE for approximately 150 h. As a result, the pH-controlled HTL layer fabricated through the solution reaction maintained the surface morphology of the perovskite layer and contributed to the stable operation of PSCs.

Efficient and flexible solar cells with improved stability through incorporation of a multifunctional small molecule at PEDOT:PSS/perovskite interface

Inverted perovskite solar cells based on poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) have drawn great attention due to their potential for foldable photovoltaic applications. Modification of the interface of PEDOT:PSS and perovskite layer is one of the approaches for improving the efficiency and stability. Here, we introduce a triphenylamine-based small molecule, N,N′-Bis-(1-naphthalenyl)-N,N′-bis-phenyl-(1,1′-biphenyl)-4,4′-diamine (NPB), into the device as the multifunctional buffer layer. It is noted that the NPB buffer layer can obviously reduce the pinholes and defects of perovskite film, and adjust the energy level mismatch between perovskite and PEDOT:PSS layer. Moreover, the carrier recombination of NPB-modified device is restricted due to the reduced defects in perovskite layer and at PEDOT:PSS/perovskite interface. As a result, the device power conversion efficiency is improved from 15.4% to 18.4%. The flexible devices are further fabricated with the best efficiency of 14.4% without hysteresis. Most importantly, due to the superior moisture and UV-light resistance of NPB, the modified device exhibits excellent long-term stability under ambient atmosphere and UV-light soaking.

Nickel sulphide nano-composite assisted hole transport in thin film polymer solar cells

Nickel sulphide (NiS) nano-composite were synthesized and used as dopant in the hole transport layer of the thin film organic solar cell (TFOSC). The nano-particles are intended to assist in the charge transport processes at the interface between the active layer and the anode. Thin film solar cells were fabricated using photo-active layer composed of poly-3-hexylthiophene (P3HT) and (6-6) phenyl-C61-butyric acid methyl ester (PCBM) blend. The solar cells employed NiS doped PEDOT:PSS hole transport layer (HTL) which are investigated in terms of changes in optical and electrical properties of the films. The electrical properties of the newly fabricated solar cells showed significant improvement in photo-generated current as the result of reduced charge carrier recombination and enhanced charge transport processes at the interface. This in turn boost the power conversion efficiency (PCE) of the devices by 95% compared to the devices without NiS doped HTL. The observed PCE enhancement is attributable to the excitation of the localized surface plasmon resonance exhibited by the presence of NiS in hole transport layer. It is noted in the investigation that the performance of the solar cell is dependant on the concentration of NiS nano-particles in PEDOT:PSS layer. As consequence, the highest recorded PCE in this study was 6.03% at 0.1% NiS by weight, which is encouraging result for device fabrication in ambient laboratory condition.

In situ construction of gradient heterojunction using organic VOx precursor for efficient and stable inverted perovskite solar cells

Inverted perovskite solar cells (PSCs) have attracted tremendous attention recently but the energy levels between the perovskite absorber and conventional hole transport layers (HTL) are mismatch, resulting in the lower open-circuit voltages (Voc) than that of regular PSCs. Herein, a gradient heterojunction (GHJ) based on poly (3,4−ethylenedioxythiophene: polystyrenesulphonate) (PEDOT:PSS)/PEDOT:PSS-VOx was constructed in situ by low-temperature annealing and used as HTL of the inverted PSCs. This GHJ structure fabricated conveniently by doping a small amount of triisopropoxyvanadium oxide isopropyl alcohol solution into the PEDOT:PSS solution during spin-coating can efficiently facilitate charge separation and improve charge extraction efficiency, leading to significantly improved PSC performance with Voc up to 1.02 V and power conversion efficiency (PCE) to 18.0%. More impressively, owing to the more hydrophobic surface and lower acidity than the PEDOT:PSS layer after the formation of high work function VOx mainly on the surface of HTL, the GHJ-based PSCs show excellent long-term stability, which retain over 80% or 70% of their initial PCEs after exposure to full spectrum illumination in N2 for 750 h or in air for 175 h, respectively. These results illustrate the significant advantages of the in situ formed VOx-modified HTLs in gradient structures using organic VOx precursors, providing important clues in constructing GHJ for inverted PSCs with high efficiency and stability.

Ellipsometric studies for thin polymer layers of organic photovoltaic cells

In this study, ellipsometry was used to study thin films on organic photovoltaic cells. The investigated cells contained a traditional donor-acceptor structure as the active layer in the form of a bulk heterojunction. The tested photovoltaic cells had the following structure: ITO/poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS)/poly (3-hexylthiophene-2-diyl) (P3HT) + 1,3-phenyl-6-fluorine-1H-pyrazolo[3,4-b]quinoline (PQ)/Al. The active layer was a blend of P3HT and a compound from the pyrazoloquinoline group with a low molecular weight marked as PQ. The ITO film acted as the electrode collecting the holes. The PEDOT:PSS layer was used to smoothen the ITO film and facilitate the transport of holes. The layers were tested using spectroscopic ellipsometry (SE), and the spectral dispersion of optical constants was determined in a wavelength range of 300–1700 nm. The appropriate theoretical models were then fitted to the SE measurement results. This information was used to determine the thickness of the layers and the dispersion relation of refractive and extinction indices. The temperature dependence of refractive indices of polythiophene layers during the heating and cooling process is also presented for a temperature range of 25–110 °C. Additionally, the authors calculated thermo-optic and thermal expansion coefficients and characterized the conditions of thermal stability of the layers and reversibility issues in thermal processes.

Suppressing Interfacial Dipoles to Minimize Open‐Circuit Voltage Loss in Quantum Dot Photovoltaics

AbstractQuantum‐dot (QD) photovoltaics (PVs) offer promise as energy‐conversion devices; however, their open‐circuit‐voltage (VOC) deficit is excessively large. Previous work has identified factors related to the QD active layer that contribute to VOC loss, including sub‐bandgap trap states and polydispersity in QD films. This work focuses instead on layer interfaces, and reveals a critical source of VOC loss: electron leakage at the QD/hole‐transport layer (HTL) interface. Although large‐bandgap organic materials in HTL are potentially suited to minimizing leakage current, dipoles that form at an organic/metal interface impede control over optimal band alignments. To overcome the challenge, a bilayer HTL configuration, which consists of semiconducting alpha‐sexithiophene (α‐6T) and metallic poly(3,4‐ethylenedioxythiphene) polystyrene sulfonate (PEDOT:PSS), is introduced. The introduction of the PEDOT:PSS layer between α‐6T and Au electrode suppresses the formation of undesired interfacial dipoles and a Schottky barrier for holes, and the bilayer HTL provides a high electron barrier of 1.35 eV. Using bilayer HTLs enhances the VOC by 74 mV without compromising the JSC compared to conventional MoO3 control devices, leading to a best power conversion efficiency of 9.2% (>40% improvement relative to relevant controls). Wider applicability of the bilayer strategy is demonstrated by a similar structure based on shallow lowest‐unoccupied‐molecular‐orbital (LUMO) levels.

A series of porphyrins as interfacial materials for inverted perovskite solar cells

Abstract Interface materials can improve the photovoltaic performance of the hybrid organic-inorganic perovskite solar cells (PSCs). Here, a series of porphyrin derivatives (metalloporphyrins: MTPPS4, M = Zn2+, Cu2+, Co2+, Ni2+; free base porphyrin: TPPS4) were developed to act as interfacial materials in PSCs. The introduction of porphyrin interlayers between PEDOT:PSS and perovskite layer in the inverted PSCs not only made energy level more matching but also improved the quality of the perovskite layer. Compared with the control device without an interlayer, the maximum power conversion efficiencies (PCE) of devices with the interlayers (in the order of ZnTPP4, CuTPP4, CoTPP4, NiTPP4 and TPP4) were increased by 23%, 25%, 21%, 17% and 13%, respectively. The highest PCE of 14.61% was based on the CuTPPS4-modified device. The porphyrins acted as the interlayers to promote carrier transport and reduce charge recombination at the interface, resulting in the increase of open-circuit voltage (VOC), short-circuit current density (JSC) and fill factor (FF).

High-performance embedded nickel grid electrodes for fast-response and bendable all-solid PEDOT: PSS electrochromic devices

Abstract Electrochromic devices are emerging as a futuristic technology for flexible electronics with the practical application values in energy-saving, displaying and military camouflage, however, the limitations in the optical, electrical and mechanical properties of the existing transparent conducting electrodes (TCEs) appear as a major obstacle for realizing high performance flexible electrochromic devices. In this work, we have proposed and demonstrated a fast-response and bendable polymer poly (3,4-ethylenedioxythiophene):poly (styrenesulfonate) (PEDOT: PSS) electrochromic device based on the embedded nickel (Ni) grid electrode. The Ni grid electrode, fabricated though patterned electroplating, has low sheet resistance (~1.3 Ω/sq), high transparency (~80%), excellent mechanical reliability and long-term chemical stability, exhibiting a figure of merit of 1250, surpassing the most existing TCEs. In addition, we have proposed a compact electrochromic architecture with the electrochromic PEDOT: PSS layer and solid polymer electrolyte being sandwiched between two embedded Ni grid electrodes. The device shows a short coloration and bleaching time (~1 s for 90% optical contrast), a high coloration efficiency (325 cm2/C) and excellent mechanical reliability (optical contrast retention ~80% after 1000 bending circles), paving a way for high performance flexible electronics.