Efficient TCO-free organic solar cells with modified poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) anodes

Organic photovoltaic cells (OPVs) with a highly conductive poly 3,4-ethylenedioxythiophene:poly styrenesulfonate (PEDOT:PSS) layer as an anode and that were modified with the addition of some organic solvents such as sorbitol (So), dimethyl sulfoxide (DMSO), N-methyl-pyrrolidone (NMP), dimethylformamide (DMF), and ethylene glycol (EG) were fabricated without the use of transparent conducting oxide (TCO). The conductivity of the PEDOT:PSS film that was modified with each additive was enhanced by three orders of magnitude. According to the atomic force microscopy (AFM) study, the conductivity enhancement might have been related to the better connections between the conducting PEDOT chains. The TCO-free solar cells with a modified PEDOT:PSS layer and an active layer composed of poly (3-hexylthiophene) (P3HT) and phenyl [6, 6] C61 butyric acid methyl ester (PCBM) performed as well as the indium-tin-oxide (ITO)-based organic solar cells. The power conversion efficiency (PCE) of the organic solar cells with a DMSO-, So + DMSO-, and EG-modified PEDOT:PSS layer reached 3.51, 3.64, and 3.77%, respectively, under an illumination of AM 1.5 (100 mW/cm2).     

Polymeric anodes from poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) for 3.5% efficient organic solar cells

We present highly efficient indium tin oxide free polymer solar cells based on poly-(3-hexylthiophene-2,5-diyl) and C₆₁-bis-butric-acid-methyl-ester (P3HT:bisPCBM) comprising a polymeric anode from highly conductive poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) formulations. The film conductivity was optimized by various additives. We found conductivities of almost 600 S/cm upon the addition of dimethylsulfoxide. The wetting properties of different PEDOT:PSS formulations were investigated by contact angle measurements. The optimized high conductivity in combination with the good film forming properties allow for the fabrication of highly efficient organic solar cells with an external power conversion efficiency of 3.5% with PEDOT:PSS as polymeric anode.     

Plasma patterning of Poly(3,4-ethylenedioxythiophene):Poly(styrenesulfonate) anodes for efficient polymer solar cells

In this work we present indium tin oxide free polymer photovoltaic devices featuring a poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) anode that has been patterned by oxygen plasma etching. By optimizing the PEDOT:PSS formulation and thickness, we achieved conductivities up to 400 S/cm. The best overall power conversion efficiency was found to be 2.2% under equivalent illumination to one sun with a PEDOT:PSS film conductivity of 300 S/cm.     

Effects of mesoscopic poly(3,4-ethylenedioxythiophene) films as counter electrodes for dye-sensitized solar cells

Counter electrode coated with chemically polymerized poly(3,4-ethylenedioxythiophene) (PEDOT) in a dye-sensitized solar cell (DSSC) was studied. The surface morphology and the nature of I⁻/I₃⁻ redox reaction based on PEDOT film were investigated using Atomic Force Microscopy and Cyclic Voltammetry, respectively. The performance of the DSSCs containing the PEDOT coated electrode was compared with sputtered-Pt electrode. We found that the root mean square roughness decreases and conductivity increases as the molar ratio of imidazole (Im)/EDOT in the PEDOT film increases. The DSSC containing the PEDOT coated on fluorine doped tin oxide glass with Im/EDOT molar ratio of 2.0, showed a conversion efficiency of 7.44% compared to that with sputtered-Pt electrode (7.77%). The high photocurrents were attributed to the large effective surface area of the electrode material resulting in good catalytic properties for I₃⁻ reduction. Therefore, the incorporation of a multi-walled carbon nanotube (MWCNT) in the PEDOT film, coated on various substrates was also investigated. The DSSC containing the PEDOT films with 0.6 wt.% of MWCNT on stainless steel as counter electrode had the best cell performance of 8.08% with short-circuit current density, open-circuit voltage and fill factor of 17.00 mA cm⁻², 720 mV and 0.66, respectively.     

导电聚(3,4-二氧乙基噻吩)应用研究进展

聚(3,4-二氧乙基噻吩)(PEDOT)是目前发现的导电态最稳定的导电高分子之一,在抗静电、塑料内存、电解电容器、有机太阳能电池、有机电致发光显示器件等领域得到了广泛研究和应用.本文简要综述PEDOT在这些领域的应用进展情况.     

Optimization of the thermoelectric figure of merit in the conducting polymer poly(3,4-ethylenedioxythiophene)

Thermoelectric generators (TEGs) transform a heat flow into electricity. Thermoelectric materials are being investigated for electricity production from waste heat (co-generation) and natural heat sources. For temperatures below 200 °C, the best commercially available inorganic semiconductors are bismuth telluride (Bi(2)Te(3))-based alloys, which possess a figure of merit ZT close to one. Most of the recently discovered thermoelectric materials with ZT>2 exhibit one common property, namely their low lattice thermal conductivities. Nevertheless, a high ZT value is not enough to create a viable technology platform for energy harvesting. To generate electricity from large volumes of warm fluids, heat exchangers must be functionalized with TEGs. This requires thermoelectric materials that are readily synthesized, air stable, environmentally friendly and solution processable to create patterns on large areas. Here we show that conducting polymers might be capable of meeting these demands. The accurate control of the oxidation level in poly(3,4-ethylenedioxythiophene) (PEDOT) combined with its low intrinsic thermal conductivity (λ=0.37 W m(-1) K(-1)) yields a ZT=0.25 at room temperature that approaches the values required for efficient devices.     

聚3,4-乙撑二氧噻吩薄膜制备的研究进展

聚3,4-乙撑二氧噻吩(PEDOT)薄膜的电导率高、稳定性好、透明性佳,有广阔的应用前景。许多科技工作者致力于PEDOT薄膜的制备研究。简要介绍了导电PEDOT薄膜制备方法的研究进展。常用的制备方法有电化学聚合法,物理涂覆法,物理沉积法,原位聚合法。     

Ultraporous poly(3,4-ethylenedioxythiophene) for nanometric electrochemical supercapacitor

Ultrathin films of poly(3,4-ethylenedioxythiophene) (PEDOT) have been prepared by electropolymerization on steel and indium-tin oxide (ITO) substrates under identical experimental conditions. Scanning electron microscopy and atomic force microscopy indicate that the substrate affects dramatically both the morphology and topography of films when the polymerization times are very short. An ultraporous three-dimensional network involving ultrathin sticks with a fiber-like morphology was formed on ITO. Asymmetric and symmetric supercapacitors have been fabricated by assembling electrodes of PEDOT deposited on ITO and steel. The specific capacitance, electrochemical stability, supercapacitor behavior and Coulombic efficiency measured for devices with an ITO/steel configuration were similar to those reported for advanced PEDOT-inorganic hybrid composites. Furthermore, the performance of the ITO/steel assembly is higher than those determined for symmetric supercapacitors derived from two identical electrodes of PEDOT deposited on steel or on ITO. The unique properties of the asymmetric supercapacitors have been attributed to the ultraporous structure of the ultrathin films deposited on ITO, which is not significantly perturbed when the device is submitted to a very high number of consecutive oxidation-reduction processes, and the different electroactivities of the two electrodes.     

Vacuum-deposited planar heterojunction polymer solar cells

The vacuum thermal evaporation of poly(3-hexylthiophene) (P3HT) for application in photovoltaic cells is demonstrated. Structural changes before and after evaporation are determined using GPC, UV-vis absorption spectroscopy, NMR, and FTIR. GPC showed that the polymer molecular weight is reduced during evaporation, leading to a blue-shift of the absorption spectra. FTIR and NMR were used to examine the change in chemical structure: it was found that conjugation remains mostly intact; however, the conjugation length decreases and side chains dissociate from the backbone. Bilayer heterojunction solar cells were fabricated by sequential deposition of P3HT and C?? and the photovoltaic response measured.     

Syntheses of titania and poly(3,4-ethylenedioxythiophene) bilayer nanotubes

Synthesis of bilayer tubes of poly(3,4-ethylenedioxythiophene) (PEDT) and titania by electrochemical polymerization of PEDT and chemical deposition of titania in the pores of anodic alumina was reported. Electron diffraction, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and fourier transformed infrared spectroscopy (FTIR) were used to characterize these bilayer tubes. SEM photographs show the tubes of uniform diameters around 200 nm. TEM photographs confirm the formation of titania and PEDT bilayer tubes of 230 nm and 100 nm diameter, the thickness of outside TiO2 layer and inner PEDT layer are around 20 nm under the experimental condition. The XPS spectra of the bilayer tubes show that the Ti2p peak shifts to a lower binding energy and S2p peak shifts to a higher binding energy. Electron diffraction patterns show that TiO2 nanotubes formed was single crystals of anatase phase. I-V characteristic curves were measured for samples prepared under various conditions.     

不同溶剂中导电聚合物PEDOT的化学氧化聚合及光谱研究

利用3,4-乙撑二氧噻吩单体和对甲苯磺酸铁,分别以异丙醇、四氢呋喃和乙氰为溶剂,用化学氧化法合成了导电聚合物聚（3,4-乙撑二氧噻吩）,3种溶剂中的反应速率有较大差异,乙氰中反应速率最快,四氢呋喃中反应速率最慢.三者的聚合产物都具有较高的电导率,但四氢呋喃中合成产物的电导率略高于另外两个产物.红外光谱和拉曼光谱显示,3种溶剂中合成的聚（3,4-乙撑二氧噻吩）在化学结构、分子共轭长度、掺杂情况等方面基本相同.     

水性乳化液中聚3,4-已撑二氧噻吩(PEDOT)低维材料的制备

实验以十二烷基苯磺酸钠(SDBS)为乳化剂,Na2S2O8为氧化剂,正己烷为油相水性乳化液中制备出聚3,4-已撑二氧噻吩(PEDOT)纳米棒和纳米球。研究了乳化剂浓度、温度、油水比、氧化剂浓度对PEDOT形貌的影响。当油水比例为1/4,乳化剂的量为1.00g,氧化剂的量为0.1626g,温度为60℃时,得到PEDOT为分布均匀规则的纳米棒,相同条件下,油水比例为1/8时,PEDOT为纳米球。油水比例为1/4,乳化剂用量为1.0g～2.0g,随乳化剂用量增加,PEDOT的形状由棒状变为球状,并且随着乳化剂用量增加,球状尺寸减小。     

Drift in the resistance of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) printed films during thermal cycling

We report on the investigation of the suitability of printed poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) films for temperature sensing devices. Gravure printing with the advantage of low cost production was used to prepare thin films of PEDOT:PSS on a flexible foil substrate. The electrical resistance was studied during thermal cycling and exposure to elevated constant temperatures. A drift of the resistance which depends on time, temperature and sample makes the usage as simple temperature sensors not possible. However, a closer look on the drift of relative resistances reveals that integrated temperature-time-profiles can be measured, which might be interesting in connection with monitoring of conditions of storing and transport of sensitive goods.     

Preparation and properties of multilayer poly(3,4-ethylenedioxythiophene) Langmuir-Blodgett film

Multilayer ultrathin film of poly(3,4-ethylene dioxythiophene) (PEDOT) was fabricated using a modified Langmuir-Blodgett (LB) method. The chemical polymerization of PEDOT occurred in the multilayer nanometer space of an as-prepared LB film by exposing the film to 3,4-ethylene dioxythiophene vapor. UV-Vis-near infrared absorption spectrum and Fourier-transform infrared spectrum techniques were applied to confirm the formation of the PEDOT ultrathin film. The results of atomic force microscopy investigation for the PEDOT LB film showed that the film surface consisted of small clusters having diameters ranging from 50 to 200 nm. X-ray photoelectron spectroscopy and secondary-ion mass spectrometry were employed to analyze the atomic composition of the PEDOT LB film and the location of the formed PEDOT. It was found that the atomic composition of the composite film was almost consistent with the theoretical value, and the PEDOT clusters were well located in different planes of the multilayer structure. The PEDOT LB film exhibited higher conductivity than conventional films and better doping/dedoping characteristics of conductivity. The sensitivity of the PEDOT LB film to NH₃ and HCl gases was also discussed.     

Novel synthesis of poly(3,4-ethylenedioxythiophene) nanotubes and hollow micro-spheres

A series of poly(3,4-ethylenedioxythiophene) (PEDOT) nanomaterials are prepared in aqueous solution without using any organic solvent, acid, surfactant and porous hard template. PEDOT can be tuned into different shapes, such as nano-tubes, spheres and vesicle-like particles by simply adjusting the experiment conditions. The different nanostructured products show similar electrochemical voltammogram behavior, though XRD and FTIR analysis indicate some different doping level and crystallity between them. The formation of different shaped polymer particles is supposed to be associated with the self assembly growth of the formed reactive EDOT species.     

Characterization of temperature-dependent carrier transport in disordered indium-tin-oxide/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)/polyfluorene/Ca/Al polymer structures

The temperature-dependent electrical characteristics of polyfluorene-based polymer structures over a temperature range from 200 to 300 K are systematically investigated in this study. Initially, using the definitions of the Berthelot-type model, it is found that the sample exhibits a higher Berthelot-type temperature T_B with high driving voltage, indicating that carrier transport in a disordered system manifests Berthelot-type behaviors. The ideal current density-voltage curve for the polymer structures given the carrier transmit mechanism is further elucidated by taking into account the ohmic conduction, trap charge limited current, and Mott and Gurney model of space charge limited current. The proposed procedure is simple and can be used to characterize the material with reasonable accuracy. We also study the density of the traps H_t, and the characteristic energy of the distribution E_t to better understand the carrier-transport process in organic materials and structures.     

The thermoelectric performance of carbon black/poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) composite films

Carbon black/poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (CB/PEDOT:PSS) composite films have been prepared by a spin-coating method. The morphology of the composite films was investigated by field emission scanning electron microscopy and atomic force microscopy. The thermoelectric properties of CB/PEDOT:PSS composite films were measured at room temperature. As the content of CB increased from 0 to 11.16 wt%, the electrical conductivity of the composite films first increased sharply and then decreased, while the Seebeck coefficient increased slowly. A highest power factor of 0.96 μWm^?1 K^?2 was obtained.     

Investigation of various commercial PEDOT:PSS (poly(3,4-ethylenedioxythiophene)polystyrene sulfonate) as a hole transport layer in lead iodide-based inverted planar perovskite solar cells

Journal of Materials Science: Materials in Electronics - Inverted-type perovskite solar cells have drawn remarkable attention due to solution-processable, straightforward configuration, low-cost...     

Charge-transport behavior in shape-controlled poly(3,4-ethylenedioxythiophene) nanomaterials: intrinsic and extrinsic factors

The charge-transport behavior in one-dimensional (1D) poly (3,4-ethylenedioxythiophene) (PEDOT) nanomaterials of three different shapes is described. Both intrinsic and extrinsic factors are considered from the viewpoint of a single nanoparticle and nanoparticle assembly. Intrinsically, the oxidation level of the 1D PEDOT nanomaterials becomes higher with increasing aspect ratio of the nanomaterials, which is closely linked to the conjugation length. This result implies that the transport properties of the nanomaterials are significantly dependent on their shape. Extrinsically, the 1D PEDOT nanomaterials make an ohmic contact with gold interdigitated microelectrodes. In addition, a strong correlation is observed between the interparticle contact resistance and the shape of the nanomaterials. Lastly, the intrinsic and extrinsic factors related to charge transport are further illustrated by the resistance changes of nanomaterial-based chemical sensors. As a result, judicious tailoring of the dimensional and geometrical characteristics of the conducting-polymer nanomaterials may enable precise control over their transport properties as well as the characteristics of the nanomaterial-based devices.     

Small-signal response of nanocrystalline-titanium dioxide/poly(3-hexylthiophene) heterojunction solar cells

Admittance spectra of nanocrystalline titanium dioxide/poly(3-hexyl thiophene), heterojunction solar cells have been measured in air and under vacuum. In air, a 3-orders of magnitude increase in capacitance is observed when the measurement frequency is decreased from 1 MHz to 0.1 Hz. The frequency-dependence of the loss tangent with zero bias voltage indicates the presence of two processes, the weaker of which is attributed to adsorbed water molecules on the surface of the nanocrystalline titanium dioxide. The second process which becomes dominant in forward bias is believed to arise from the presence of an interfacial capacitance. In air, the capacitance is seen to depend strongly on applied forward bias consistent with the presence of an interfacial depletion region. However, a number of inconsistencies indicate that a mechanism related to carrier interaction with oxygen-related interface states may be the cause. At high forward bias and low frequencies, a negative incremental capacitance is observed similar to that seen in organic light emitting diodes following the onset of double-injection.