Effect of sorbitol doping in PEDOT:PSS on the electrical performance of organic photovoltaic devices

Organic photovoltaic cells have important advantages, such as low cost and mechanical flexibility. The conducting polymer poly(3,4 ethylenedioxy-thiophene):poly(styrene sulfonate) (PEDOT:PSS) has been widely used as an interfacial layer or a polymer electrode in polymer electronic devices, such as photovoltaic devices and light-emitting diodes. In this report, we discuss the direct current (DC) conductivity of PEDOT:PSS films containing various weight ratios of sorbitol dopant. The work function is shown to steadily decrease with increasing dopant content. With different dopant contents, illuminated current–voltage photovoltaic characteristics were observed. Ultraviolet photoelectron spectroscopy (UPS) analysis revealed that the work function of the PEDOT:PSS was affected by its sorbitol content. The morphologies of the doped PEDOT:PSS films were characterized by atomic force microscopy (AFM). For the device fabrication, we made organic photovoltaic cells by a spin-coating process and Al deposition by thermal evaporation. The sorbitol dopant is able to improve the efficiency of the device.     

掺杂PEDOT ∶PSS对聚合物太阳能电池性能影响的研究

研究了掺杂后poly(3,4-ethylene dioxythiophene):poly(styrenesulphonic acid)(PEDOT ∶PSS)电导率的变化以及掺杂PEDOT ∶PSS薄膜对聚合物太阳能电池器件性能的影响. 实验发现,向PEDOT ∶PSS中掺入极性溶剂二甲基亚砜(DMSO)明显提高了薄膜的电导率,掺杂后的电导率最大值达到1.25 S/cm,比未掺杂时提高了3个数量级. 将掺杂的PEDOT ∶PSS薄膜作为缓冲层应用于聚合物电池 (ITO/PEDOT ∶PSS/P3HT ∶PCBM/LiF/Al) 中,发现高电导率的PEDOT ∶PSS降低了器件的串联电阻,增加了器件的短路电流,从而提高了器件的性能. 最好的聚合物太阳能电池在100 mW/cm²的光照下,开路电压(V_oc)为0.63 V,短路电流密度(J_sc)为11.09 mA·cm^-2,填充因子(FF)为63.7%,能量转换效率(η)达到4.45%. 关键词： PEDOT ∶PSS 电导率 聚合物太阳能电池 能量转换效率     

稀释溶剂对PEDOT∶PSS薄膜和有机太阳能电池性能的影响

采用喷涂技术制备聚3,4-乙撑二氧噻吩∶聚苯乙烯磺酸盐(PEDOT∶PSS)有机层薄膜,系统研究了乙醇、去离子水、甲醇、异丙醇和乙二醇等稀释溶剂对PEDOT∶PSS薄膜形貌、透过率及导电性能的影响。将PEDOT∶PSS薄膜应用于有机太阳能电池器件的制备,研究了不同溶剂对器件性能的影响。实验结果表明:采用乙醇稀释PEDOT∶PSS溶液,能有效抑制PEDOT∶PSS颗粒团聚,降低薄膜粗糙度,提高薄膜的透过率和导电性。以其制备的太阳能电池器件的能量转换效率明显高于其他溶剂稀释,转换效率为2.66%。     

Increased work function in PEDOT:PSS film under ultraviolet irradiation

An increase of work function （0.3 eV） is achieved by irradiating poly（3,4-ethylenedioxythiophene）：poly（styrene sul- fonate） （PEDOT：PSS） film in vacuum with 254-nm ultraviolet （UV） light. The mechanism for such an improvement is investigated by photoelectron yield spectroscopy, X-ray photo electron energy spectrum, and field emission technique. Sur- face oxidation and composition change are found as the reasons for work function increase. The UV-treated PEDOT：PSS film is used as the hole injection layer in a hole-only device. Hole injection is improved by UV-treated PEDOT：PSS film without baring the enlargement of film resistance. Our result demonstrates that UV treatment is more suitable for modifying the injection barrier than UV ozone exposure.     

Effect of annealing on performance of PEDOT:PSS/n-GaN Schottky solar cells

We develop a heterojunction-based Schottky solar cell consisting of n-type GaN and PEDOT：PSS and also investigate the effect of annealing on the performance of the solar cell. The results show that the open circuit voltage （Voc） increases from 0.54 V to 0.56 V, 0.71 V and 0.82 eV while decreases to 0.69 eV after annealing at 100 ℃, 130 ℃, 160 ℃, and 200 ℃, respectively, which can be ascribed to the change of barrier height of PEDOT：PSS/GaN Schottky contact induced by variation of the work function of the PEDOT：PSS. Furthermore, the conductivity and surface roughness measurements of the PEDOT：PSS indicate that annealing can increase the grain size and improve the connectivity between PEDOT and PSS particles, and cause thermal degradation at the same time, which leads to the rise in short-circuit current density （ISC） up to 160 ℃ and the dropoff in ISC after annealing at 200 ℃.     

Solid Contact Micropipette Ion Selective Electrode for Potentiometric SECM

New solid contact ammonium micropipette electrodes (ISE), well applicable in scanning electrochemical microscopy are reported. The solid contact was made of a PEDOT nanowire coated carbon fiber, lowered down close to the orifice, and dipped inside the cocktail being in the pipette tip. This configuration provided low electrical resistance and good potential stability. Submicron tip size, usual in case of micropipette ISE‐s easily can be fabricated in this way. The applicability of the electrode in SECM has been proved in SG/TC mode imaging urease enzyme active spots in urea solutions.     

Development of an Innovative Nitrite Sensing Platform Based on the Construction of an Electrochemical Composite Sensor of Polymer Coated CNTs and Decorated with Magnetite Nanoparticles

Electrochemical determination of nitrite in real water samples is achieved using simple and efficient electrochemical sensor. The sensor is fabricated by electrodeposition of a thin layer of poly(3,4-ethylenedioxythiophene) sandwiched by drop-casting two thin layers of CNTs and iron oxide nanoparticles (Fe₃O₄) over a GC electrode surface. Voltammetry determination of nitrite in tap water and wastewater samples in the concentration range (0.5–150 μM) is successfully achieved with detection limits of 22 and 24 nM, respectively. Practical application of the GC/CNT/PEDOT/Fe₃O₄ sensor is efficiently assessed in real water samples for nitrite determination with acceptable recoveries, excellent anti-interference ability and long-term stability.     

Aptamer‐Assisted Gold Nanoparticles/PEDOT Platform for Ultrasensitive Detection of LPS

Neatly arranged gold nanoparticles (AuNPs) were directly electrodeposited on an electrochemically polymerized self‐assembled monolayer (SAM) of thiol‐functionalized 3,4‐ethylenedioxythiophene (EDOT) derivative, EDTMSHA. A thiolated single‐stranded DNA (ssDNA) aptamer with high specificity to LPS was immobilized on the AuNPs/conducting polymer composite film, serving as sensing platform for LPS detection. Electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), scanning electron microscope (SEM), and atomic force microscopy (AFM) were utilized to characterize the modification and detection processes. The electron transfer resistance was found to have a linear relationship with LPS concentration from 0.1 pg/mL to 1 ng/mL.     

Synthesis and characterization of monosubstituted and disubstituted poly(3,4‐propylenedioxythiophene) derivatives with high electrochromic contrast in the visible region

Monosubstituted and disubstituted 3,4‐propylenedioxythiophenes were synthesized and polymerized by both chemical and electrochemical methods. All the monomers were characterized for their molecular structures, and the polymers were characterized for their electrochemical properties. The disubstituted derivatives showed higher contrast than the corresponding monoalkyl derivatives. The highest electrochromic contrast of 89% was exhibited by a dibenzyl derivative, but the derivative was insoluble. On the other hand, the electrochemically polymerized dihexyl‐ and didodecyl‐substituted poly(3,4‐propylenedioxythiophene)s exhibited 74 and 77% electrochromic contrast, respectively, and were soluble. The molecular weights of the chemically and electrochemically synthesized polymers were analyzed by gel permeation chromatography. The chemically synthesized polymers showed higher molecular weights. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 419–428, 2005     

Chemical synthesis and characterization of poly(3,4-ethylenedioxythiophene)/tungsten composite materials in the presence of ionic liquids

Poly(3,4-ethylenedioxythiophene)/tungsten (PEDOT/W) composites were prepared by an in situ chemical oxidative polymerization of 3,4-ethylenedioxythiophene in different ionic liquids; 1-butyl-3-methylimidazolium tetrafluoroborate (BMIMBF₄), 1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF₆), 1-butyl- 3-methylimidazolium bis(trifluoromethylsulfonyl) imide (BMIMTFSI), and 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl) imide (BMPTFSI). These polymer/metal hybrids (PEDOT/W) were subsequently characterized for their structural, crystalline, thermal and morphological properties by Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). The significant enhancement in properties can be attributed to the nanoscale particle size and uniform size distribution of PEDOT/W and the synergistic effect between the inorganic nano-W and organic PEDOT material.