Comparison of performance parameters of poly(3,4 ethylenedioxythiophene) (PEDOT) based electrochromic device on glass with and without counter electrode

Conjugated polymers are promising materials for electrochromic device technology. Aqueous dispersions of poly(3,4-ethylenedioxythiophene)-(PEDOT) were spin coated onto transparent conducting oxide (TCO) coated glass substrates. A seven-layer electrochromic device was fabricated with the following configuration: glass/transparent conducting oxide (TCO)/PEDOT (main electrochromic layer)/gel electrolyte/prussian blue (counter electrode)/TCO/glass. The device fabricated with counter electrode (Prussian blue) showed a contrast of 18% and without counter electrode showed visible contrast of 5% at 632 nm at a voltage of 1.9 V. The comparison of the device is done in terms of the colouration efficiency of the devices with and without counter electrode.     

Towards the improvement of attenuation range and response time of electrochromic polymer-based variable optical attenuators

A solid–liquid electrochromic variable optical attenuator device consisting of a thin layer of LiClO₄-doped poly(3,4-ethylenedioxythiophene) (PEDOT) and ferrocene in propylene carbonate has been demonstrated to exhibit a large dynamic range of optical attenuation at the telecommunication wavelength of 1550 nm. Doping of PEDOT film with an electrolyte greatly improves the device performance in terms of optical attenuation or color efficiency at 1550 nm and response time. An optimized single-layer device consisting of LiClO₄-doped PEDOT film (440 nm) shows a 10-dB dynamic range of optical attenuation at 1550 nm, a low optical loss of 0.86 dB for the bleached state, and a response time of 5–7 s at the switching potential of 0–2 V.     

Electrosynthesis and characterization of a multielectrochromic copolymer of 1,4-bis(2-thienyl)-naphthalene with 2,2′-bithiophene

Electrochemical copolymerization of 1,4-bis(2-thienyl)-naphthalene (BTN) and 2,2′-bithiophene (BT) is carried out in acetonitrile (ACN) containing sodium perchlorate (NaClO₄) as a supporting electrolyte. Cyclic voltammetry (CV), UV-vis and FT-IR analyzes confirm that the resulting polymer is a copolymer rather than a blend or a composite of the respective homopolymers. The obtained P(BTN-co-BT) film exhibits five different colors (orange yellow, yellowish green, green, greenish blue and blue) under various potentials, revealing distinct electrochromic properties from that of the BTN homopolymer film. Maximum contrast (ΔT%) and response time of the copolymer film are measured as 32.7% and 0.59 s at 750 nm. Electrochromic device (ECD) based on P(BTN-co-BT) and poly(3,4-ethylenedioxythiophene) (PEDOT) is also constructed and characterized. This ECD shows a maximum optical contrast (ΔT%) of 24.2% in visible region with a response time of 0.32 s at 780 nm. The coloration efficiency (CE) of the device is calculated to be 308 cm² C⁻¹ at 780 nm.     

Electrochromic properties of self-assembled nanoparticle multilayer films

Hexagonal tungsten bronze (HTB) nanocrystal and TiO₂ nanoparticles were assembled into thin films by layer-by-layer self-assembly method. HTB nanocrystals were synthesized by hydrothermal route at 155 °C. UV-Vis spectra showed that the HTB/TiO₂ films exhibit a linear increase in film thickness with assembly exposure steps. The electrochromic property of the film was carefully investigated. Cyclic voltammetry indicated that the redox peak was around −0.5 V. The electrochromic contrast, coloration efficiency, switching speed, stability and optical memory were carefully investigated. The films vary from white to blue and finally dark brown. The electrochromic contrast is 63.9% at 633 nm. The coloration efficiency of the films is relatively high. The response time is less than 3 s.     

Effects of oxygen stoichiometry on electrochromic properties in amorphous tungsten oxide films

We have investigated the electrochromic properties of amorphous granular tungsten oxide (WO_3 + δ) thin films with over-stoichiometric oxygen content (δ), using LiClO₄ with propylene carbonate as an electrolyte. Different optical and electrochromic characteristics are observed with increasing δ. All the devices are electrochemically stable for more than 5000 color/bleach cycles without apparent degradation, and they have a faster response to coloration than to bleaching. WO_3 + δ films with an optimized δ value show an optical modulation of 86% at a wavelength of 630 nm and the highest coloration efficiency ever reported of ~ 213 cm²/C. The δ-dependent coloration mechanism is discussed using the site saturation model. It is proposed that WO_3 + δ films with the optimal δ value have favorable thickness and stoichiometry for the generation of Li⁺W⁺⁵ states.     

NiO/PB复合电致变色薄膜的制备及其性能研

采用水热法制备了垂直生长的氧化镍(NiO)纳米片薄膜, 并利用电沉积法将普鲁士蓝(PB)负载到NiO纳米片薄膜上, 制备了新型的NiO/PB复合电致变色薄膜。利用X射线衍射仪(XRD)、场发射扫描电镜(SEM)对样品的晶型以及微观形貌进行了表征, 采用紫外-可见光光度计以及电化学工作站对NiO/PB复合薄膜的电化学和电致变色性能进行了研究和表征。结果表明: NiO/PB复合电致变色薄膜具有多孔结构和较大的比表面积, 可以增大电解质与电极材料的接触面积。PB成功负载到NiO薄膜表面, 使NiO/PB复合薄膜表现出较大的电流密度。相比于单层NiO薄膜, NiO/PB复合薄膜表现出更好的电致变色性能, 其光调制范围可以达到46%, 着色效率为141 cm²/C, 并且其着色时间可以缩短到5 s, 褪色时间为6 s。     

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.     

Optical modeling of organic solar cells based on CuPc and C60

We have investigated the influence of the poly(3,4-ethylenedioxythiophene)-blend-poly(styrene-sulfonate) (PEDOT:PSS) layer on the short-circuit current density (J(sc)) of single planar heterojunction organic solar cells based on a copper phthalocyanine (CuPc)-buckminsterfullerene (C(60)) active layer. Complete optical and electrical modeling of the cell has been performed taking into account optical interferences and exciton diffusion. Comparison of experimental and simulated external quantum efficiency has allowed us to estimate the exciton diffusion length to be 37 nm for the CuPc and 19 nm for the C(60). The dependence of short-circuit current densities versus the thickness of the PEDOT:PSS layer is analyzed and compared with experimental data. It is found that the variation in short-circuit current densities could be explained by optical interferences.     

Color combination of conductive polymers for black electrochromism

Conducting polymers that absorb three primary colors, red, green, and blue (RGB), were introduced with a yellow electrochromic polymer (Y) for the preparation of black electrochromic devices. Red poly(3-hexylthiophene) (P3HT) and blue poly(3,4-ethylenedioxythiophene) (PEDOT) were coated on one side of the electrode as a cathodically coloring electrochromic (EC) layer, while green poly(aniline-N-butylsulfonate) (PANBS) and yellow EC poly{[1,3-bis(9',9'-dihexylfluoren-20-yl)azulenyl]-alt-[2",7"-(9",9"-dihexylfluorenyl]} (PDHFA) were coated on the opposite electrode to complete a complementary EC device. The yellow PDHFA layer effectively compensated for absorption below 450 nm and above the 600 nm region, which was lacking in the RGB electrode. The resultant RGBY ECD provided a black color near the CIE black with L*, a*, and b* values of 32, -1.1, and 3.7, respectively, covering a broad absorption in the visible range in the colored state. The state of the black EC device was maintained, even after the electricity was turned off for 200 h, showing stable memory effect.     

Roll‐to‐Roll Production of Graphene Hybrid Electrodes for High‐Efficiency,Flexible Organic Photoelectronics

Despite nearly two decades of research, the absence of ideal, flexible, and transparent electrodes has been the biggest bottleneck for realizing flexible and printable electronics via roll‐to‐roll (R2R) method. A fabrication of poly(3,4‐ethylenedioxythiophene):poly(styrene sulfonate):graphene:ethyl cellulose (PEDOT:PSS:G:EC) hybrid electrodes by R2R process, which allows for the elimination of strong acid treatment. The high‐performance flexible printable electrode includes a transmittance (T) of 78% at 550 nm and a sheet resistance of 13 Ω sq⁻¹ with excellent mechanical stability. These features arise from the PSS interacting strongly with the ethyoxyl groups from EC promoting a favorable phase separation between PEDOT and PSS chains, and the highly uniform and conductive G:EC enable rearrangement of the PEDOT chains with more expanded conformation surrounded by G:EC via the π–π interaction between G:EC and PEDOT. The hybrid electrodes are fully functional as universal electrodes for outstanding flexible electronic applications. Organic solar cells based on the hybrid electrode exhibit a high power conversion efficiency of 9.4% with good universality for active layer. Moreover, the organic light‐emitting diodes and photodetector devices hold the same level to or outperform those based on indium tin oxide flexible transparent electrodes.     

Nanoimprint of dehydrated PEDOT:PSS for organic photovoltaics

We demonstrate the fabrication of poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) nanogratings by a dehydration-assisted nanoimprint lithographic technique. Dehydration of PEDOT:PSS increases its cohesion to protect the nanostructures formed by nanoimprinting during demolding, resulting in the formation of high quality nanogratings of 60?nm in height, 70?nm in width and 70?nm in spacing (aspect ratio of 0.86). PEDOT:PSS nanogratings are used as hole transport and an electron blocking layer in blended poly(3-hexylthiophene-2,5-diyl) (P3HT):[6,6]-penyl-C61-butyric-acid-methyl-ester (PCBM) organic photovoltaic devices (OPV), showing enhancement of photocurrent and power efficiency in comparison to OPV devices with non-patterned PEDOT:PSS films.     

Reflective and Complementary Transmissive All-Printed Electrochromic Displays Based on Prussian Blue

By combining the electrochromic (EC) properties of Prussian blue (PB) and poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS), complementary EC displays manufactured by slot-die coating and screen printing on flexible plastic substrates are reported. Various display designs have been realized, resulting in displays operating in either transmissive or reflective mode. For the transmission mode displays, the color contrast is enhanced by the complementary switching of the two EC electrodes PB and PEDOT:PSS. Both electrodes are either exhibiting a concurrent colorless or blue appearance. For the displays operating in reflection mode, a white opaque electrolyte is used in conjunction with the EC properties of PB, resulting in a display device switching between a fully white state and a blue-colored state. The developments of the different device architectures, that either operate in reflection or transmission mode, demonstrate a scalable manufacturing approach of all-printed EC displays that may be used in a large variety of Internet of Things applications.     

Photo and electroluminescence of a platinum porphyrin doping of complexes with two metal cores

In this paper, four new complexes with two metal cores [2Sm, 2Sn, 2Zn and 2Pb] were prepared and utilized as host material in in the electroluminescence (EL) devices. Devices with two metal cores and with the structure of ITO/PEDOT: PSS (60 nm)/PVK (55 nm)/[2Sm, 2Sn, 2Zn and 2Pb]: %8 [2,5PtTPP] (45 nm)/Al (200 nm) were fabricated, A blue–green photoluminescence (PL) emission with a blue shift compared to the 2,5PtTPP was observed. 2,5PtTPP doped in 2Sm and 2Sn showed more pure red color compared to 2Zn and 2Pb based devices. We believe that energy transfer occurring at 2,5PtTPP/[2Sm, 2Sn] molecules is responsible for the red color in the EL of the device. The electronic effect of two metal cores of complexes influenced the maximum current density, brightness, and luminous efficiency of the devices. Finally, we have demonstrated the samarium complex of 8-hydroxyquinoline is a promising host material for red OLEDs with high efficiency and has a simple device structure.     

Enhancing the performance of an electrochromic device by template synthesis of the active layers

This work describes the use of template synthesis to produce materials with optimized properties to be used in electrochromic devices. A composite prepared by the inclusion of polyaniline within the pores of a cellulose acetate was used as primary electrochromic layer and a porous V_{2 5} phase was used as an auxiliary electrode to counter balance the charge in the entire device. The device closed with a gel polymer electrolyte exhibited a very high optical contrast (light yellow to dark blue) with ΔT_{750 nm}=78%. However, the optical response time indicates a slow ion exchange during electrochromic cycles. By comparing the voltammogram and the curve obtained by differentiation of the absorbance variation with time, it was possible to identify the contribution of each redox couple to the total color change.     

Electromechanically driven variable-focus lens based on transparent dielectric elastomer

Dielectric elastomers with low elastic stiffness and high dielectric constant are smart materials that produce large strains (up to 300%) and belong to the group of electroactive polymers. Dielectric elastomer actuators are made from films of dielectric elastomers coated on both sides with compliant electrode material. Poly(3,4-ethylenedioxythiophene) (PEDOT), which is known as a transparent conducting polymer, has been widely used as an interfacial layer or polymer electrode in polymer electronic devices. In this study, we propose the transparent dielectric elastomer as a material of actuator driving variable-focus lens system using PEDOT as a transparent electrode. The variable-focus lens module has light transmittance up to 70% and maximum displacement up to 450. When voltage is applied to the fabricated lens module, optical focal length is changed. We anticipate our research to be a starting point for new model of variable-focus lens system. This system could find applications in portable devices, such as digital cameras, camcorder, and cell phones.     

Novel electrochromic devices based on complementary nanocrystalline TiO2 and WO3 thin films

Electrochromic devices were elaborated based on two complementary electrodes made of a nanocrystalline metal oxide thin film deposited on conducting glass. The first electrode holds a 5 μm thick nanocrystalline TiO₂ film derivatized by a monolayer of a phosphonated triarylamine which can be rapidly oxidized by electron transfer to the conducting support followed by charge percolation inside the monolayer. The oxidation in accompanied by a blue coloration due to the absorption band at 730 nm of the stable triarylamminum radical cation. The second electrode bears a 0.2 μm thick nanocrystalline WO₃ film which turns from colorless to blue by reduction and lithium ion insertion. The former electrode reaches an absorbance of at least 3 between 700 and 730 nm after full oxidation (16 mC/cm²) at 1.0 V vs. NHE while for the second, complete reduction at −1.3 V (74 mC/cm²) leads to A=2.4 at 774 nm. An electrochromic device comprising both electrodes separated by an electrolytic solution of 0.1 Li⁺ in 4,7-dioxaoctanitrile reaches an absorbance of 2.2 at 700 nm, 4 s after a voltage step to 1.5 V. The system was shown to sustain at least 14400 coloration-discoloration cycles without degradation.     

Structure-based color of natural petals discriminated by polymer replication

The optical appearance of many flowers in nature relies on their inherent pigments ("chemical color") as well as on the surface structure of the epidermis ("structural color"). The structural color is created by a combination of regular and irregular micro- and nanosized features. With a red rose petal as a biological template, we have separated the structural coloration from the chemical coloration by reproducing the petal's intricate surface structure in a pigment-free polymer. UV-vis reflectance measurements of the templates showed that the pigment-induced chemical coloration of the red-rose petal results in intense absorption and reflection in the green (～550 nm) and red (～700 nm) spectral region, respectively. The micro- and nanosized structural hierarchy on the petal surface, on the other hand, induced a modulation of the optical reflectivity and a filtering effect in specific wavelength ranges. More notably, we observed that a variation in the size of the micro/nanostructures on the petal surface leads to an effective modulation of the reflectance. These results could provide useful tips for the design of bioinspired optical devices, emulating natural petal structures.     

Thin-film photodetectors for the vacuum ultraviolet spectral region

We report on thin-film photodetectors optimized for detecting the vacuum UV and rejection of the visible spectrum of electromagnetic radiation. The devices are made of hydrogenated amorphous silicon and silicon carbide on a glass substrate. At room temperature the photodetectors exhibit quantum efficiencies of 52% at lambda = 58.4 nm, 1% at lambda = 400 nm, and 0.1% at lambda = 650 nm. The response time for UV pulses from an N(2) laser gives signals of 6-mus full width at half-maximum and 500-ns rise time.     

Efficient organic photovoltaic devices by using PEDOT:PSSs with excellent hole extraction ability

We have demonstrated the poly(3-hexyl-thiophene-1,5-diyl) (P3HT):[6,6]-phenyl C61-butyric acid methyl ester (PCBM) bulk heterojunction (BHJ) organic photovoltaic (OPV) devices on various poly(3,4-ethylene-dioxythiophene):poly(styrenesulfonate) (PEDOT:PSSs). The device with PEDOT:PSS of PH 500 adding 1% dimethyl sulfoxide (DMSO) showed the best performances in term of the fill factor and power conversion efficiency (PCE) than others. The hole extraction ability of PEDOT:PSS is very important to balance between holes and electrons mobility because the carrier mobility of PCBM (approximately 10(-4) cm2/Vs) is higher than that of P3HT (approximately 10(-6) cm2/Vs) in P3HT:PCBM BHJ structure. The optimized BHJ OPV with PEDOT:PSS of PH 500 adding 1% DMSO showed a short-circuit current density of 8.92 mA/cm2 and a PCE of 2.97%, which was nearly increased to 2.5 times than that of control device with PEDOT:PSS of P VP Al 4083.     

Efficiency enhancement of polymer solar cells with Ag nanoparticles incorporated into PEDOT:PSS layer

In this study, large-sized silver nanoparticles (Ag NPs) (average size: 80 nm) have been introduced into the anodic buffer poly-(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) layer (thickness: about 55 nm) of poly(3-hexylthiophene):[6,6]-phenyl-C61-butyric acid methyl ester bulk heterojunction polymer solar cells. The results showed that the short-circuit current density can increase from 8.73 to 11.36 mA/cm², and power conversion efficiency increases from 2.28 to 2.65 % when 0.1 wt% Ag NPs was incorporated in PEDOT:PSS layer, corresponding to an efficiency improvement of 16.2 %. Absorption spectrums of the active layers indicate that large-sized Ag NPs have no clear contribution to optical absorption improvement. By measuring the conductivity of PEDOT:PSS films without and with Ag NPs and analyzing device structure of this polymer solar cell, it was founded that the improvements in power conversion efficiency was originated from higher conductivity of PEDOT:PSS layer incorporated with Ag NPs and the shorter routes for holes to travel to the anode.