Toward fully printed organic photovoltaics: processing and stability (original) (raw)
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Towards low cost, efficient and stable organic photovoltaic modules
2010
The presence of a transparent conductive electrode such as indium tin oxide (ITO) limits the reliability and cost price of organic photovoltaic devices as it is brittle and expensive. Moreover, the relative high sheet resistance of an ITO electrode on flexible substrates limits the maximum width of a single cell. Holst Centre and ECN have developed an alternative ITO-free transparent anode, based on a solution processed high conductive and transparent PEDOT:PSS layer in combination with a printed current collecting grid. Screen printed silver grids can yield sheet resistances down to 1 Ohm/Sq with a surface coverage of only ca 5%. The efficiency of a flexible device with an active area of 4 cm 2 with such a grid is much higher than a similar device based on ITO. Furthermore, as this composite anode is solution-processed, it is an important step forward towards low-cost large area processing. Moreover, initial experiments indicate that the stability of ITO-free devices is higher than the stability of standard devices based on ITO. This work will ultimately contribute toward fully printed devices, which will provide low-cost manufacturing and improved stability of organic photovoltaic modules.
ITO-free flexible organic solar cells with printed current collecting grids
Solar Energy Materials and Solar Cells, 2011
The presence of a transparent conductive electrode such as indium tin oxide (ITO) limits the reliability and cost price of organic photovoltaic devices as it is brittle and expensive. Moreover, the relative high sheet resistance of an ITO electrode on flexible substrates limits the maximum width of a single cell. We have developed an alternative ITO-free transparent anode, based on solution processed high conductive PEDOT:PSS in combination with a printed current collecting grid. The screen printed silver grid demonstrates a typical sheet resistance of 1 O/& with 6.4-8% surface coverage. The efficiency of a flexible device with an active area of 4 cm 2 with such a grid is much higher than a similar device based on ITO. Furthermore, as this composite anode is solution-processed, it is a step forward towards low-cost large area processing.
Organic Electronics
In this report, surface engineering is used to improve the air-stability of direct polymer solar cells by replacing the PEDOT:PSS hole transporting layer (HTL) by a grafted polymeric layer. For that purpose a poly(3-hexylthiophene) bearing a triethoxysilane function at the end of the chain (P3HT-Si) was synthesized and anchored to the indium-tin oxide (ITO) electrode. The different characterization techniques used (UV-visible and X-ray photoemission spectroscopy) showed that the applied temperature during grafting is a determinant parameter to tune the P3HT-Si layer thickness/density. For low temperature grafting, polymeric chains were laying close to the surface while higher grafting temperature led to polymeric chains pointing upwards. This organization of the polymeric chains in the grafted layer has a direct impact on photovoltaic properties of the devices fabricated with P3HT-Si as HTL. The use of this new self-assembled HTL creates a hole selective membrane which drastically reduces the leakage current. As a result, the power conversion efficiency of such devices was improved compared to devices with bare ITO. Additionally, by replacing PEDOT:PSS by the hydrophobic P3HT-Si, the water penetration in the device is impeded which significantly improved the shelf lifetime of devices.
Gravure‐printed PEDOT:PSS on flexible PEN substrate as ITO‐free anode for polymer solar cells
Polymer Composites, 2015
In this work, highly conductive and transparent films based on poly(3,4 ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) doped with dimethyl sulfoxide (DMSO) were printed onto a flexible substrate, the polyethylene naphthalate (PEN), using the gravure printing method. Gravure-printed DMSO-PEDOT:PSS ink suitably modified with isopropanol was developed and used as anode in flexible solar cells replacing the commonly used anode, that is, Indium Tin Oxide (ITO). Several inks were prepared and characterized in terms of viscosity and surface energy and tested by gravure printing. The wettability of the PEN substrate was investigated through contact angle measurements. For comparison, the anodic conductive polymer was also spin coated on the PEN substrate using an ink suitable for this technique. The films produced with both the techniques, gravure printing and spin coating, each using a proper ink, were characterized in terms of structure and physical-chemical properties. The printed layers were employed as anodes into ITO freepolymer solar cells based on a bulk heterojunction of Poly({4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b 0 ]dithiophene-2,6-diyl}{3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno-[3,4-b]thiophenediyl}) (PTB7) and [6,6]-phenyl C 70-butyric acid methyl ester ([70]PCBM). The performances of the devices with printed and spin coated polymeric anode were compared. The cell with the spin-coated anode reached a power conversion efficiency of 3% while the corresponding device with the printed anode a value around 2%.
A Versatile Technique for the Fabrication of PEDOT: PSS Films for Organic Solar Cells
2012
Organic solar cells hold the potential of low-cost production as compared to inorganic solar cells, as well as the increase in efficiency. To realize these possibilities, the key is to fabricate most of the functional films in requisite structures via ambient solution-processed techniques. The PEDOT: PSS films, which are commonly used as an anode layer in organic electronic devices, were deposited on large-area ITO glass substrates under optimized conditions. The spin, spray, brush and brush+spray-coating techniques were utilized to examine their suitability in the fabrication of organic solar cells (OSCs). The films were characterized for their morphology, molecular structure, optical and electrical properties and results are compared with the existing data. A smooth and thin films of PEDOT: PSS were obtained by "Spray+Brush" coating method with attractive sheet-conductivity having potential in fabricating OSCs with different architectures.
2014
The need for inexpensive alternative to indium doped tin oxide (ITO) transparent electrodes is imminent for cost-efficient solution processed optoelectronic applications. ITO-free transparent electrodes can be based on inkjet-printed Silver (Ag) nanoparticles grids embedded into PEDOT:PSS buffer layers. We present an in-depth investigation of the morphological evolution of the inkjet printed Ag nanopartricle sintering process combined with an ultimate control of the printed grid design requirements for efficient ITO-free organic photovoltaics (OPVs). We report on glass/ITO-free P3HT:PC 60 BM and Si-PCPDTBT: PC 70 BM based OPVs with power conversion efficiency of 2.8% and 4.9% respectively. These devices exhibited minimal losses when compared to reference ITO-based OPVs.
Journal of Solid State Electrochemistry, 2018
In this article, controlled changes on morphology, thickness, and band gap of poly[ethylenedioxythiophene] (PEDOT) polymer films fabricated by electrochemical polymerization (potentiostatically) are analyzed. Electropolymerization of the monomer ethylenedioxythiophene (EDOT) was carried out on indium tin oxide (ITO) electrodes, in different dry organic electrolytic media, such as acetonitrile, acetonitrile-dichloromethane, and toluene-acetonitrile mixtures. It was found that electropolymerization kinetics can be controlled by changing the polarity of the electrolytic media, and kinetics is slower for those with low polarity. This fact combined with an accurate control of EDOT monomer concentration and electropolymerization at E peak/2 potential, allows to control the morphology and thickness of the electropolymerized PEDOT films (E-PEDOT:ClO 4); toluene/ACN (4:1, v/v) and [EDOT] = 0.3 mM gave the best films for application in organic photovoltaic (OPV) cells. The performance of the E-PEDOT:ClO 4 films was tested on ITO electrodes as anode buffer layer in OPV cells with the configuration ITO/E-PEDOT:ClO 4 /P3HT:PC 61 BM/Field's metal, where Field's metal (cathode) is a eutectic alloy that lets to fabricate OPV devices easily and in a fast and economical way at free vacuum conditions. The performance of these devices was compared with an OPV device constructed with a buffer layer anode, prepared using the classical spin coating of PEDOT:PSS on ITO. Results showed that OPV cells fabricated with E-PEDOT:ClO 4 have a slightly increased PV performance.
Printable anodes for flexible organic solar cell modules
Thin Solid Films, 2004
The performance of organic bulk donoryacceptor heterojunction solar cells with different transparent electrodes is compared. Up to now, expensive material like indium-tinoxide (ITO) has been commonly used as a transparent electrode. Nevertheless, an interesting organic alternative in the form of highly conductive poly(3,4-ethylenedioxythiophene)ypoly(styrenesulfonate) (PEDOTy PSS) is emerging. In this work, a comparison is made between cells with either ITO or highly conductive PEDOTyPSS as a transparent contact. Different techniques such as spin-coating and screen-printing are used to deposit this latter material. Owing to still limited conductivity of PEDOTyPSS with respect to ITO, an underlying metallic grid is introduced. A standard photographic technique optimised here to result in a metallic Ag-pattern is used. In this way, a comparable performance of the photovoltaic devices with either type of anodes is obtained. This newly developed PEDOTyPSS-based transparent anode is successfully applied onto flexible substrates. Furthermore, appropriate design of the device structure makes it possible to realise serially connected solar cells. The performance of such devices is also reported. These results show that industrial production of fully flexible organic solar cell modules will be possible at low costs. ᮊ
Scientific Reports, 2021
Poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) mixed with single-wall nanotubes (SWNTs) (10:1) and doped with (0.1 M) perchloric acid (HClO4) in a solution-processed film, working as an excellent thin transparent conducting film (TCF) in organic solar cells, was investigated. This new electrode structure can be an outstanding substitute for conventional indium tin oxide (ITO) for applications in flexible solar cells due to the potential of attaining high transparency with enhanced conductivity, good flexibility, and good durability via a low-cost process over a large area. In addition, solution-processed vanadium oxide (VOx) doped with a small amount of PEDOT-PSS(PH1000) can be applied as a hole transport layer (HTL) for achieving high efficiency and stability. From these viewpoints, we investigate the benefit of using printed SWNTs-PEDOT-PSS doped with HClO4 as a transparent conducting electrode in a flexible organic solar cell. Additionally, we applied a VOx-PE...