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A common approach to bulk heterojunction solar cells involves a ˵trial-and-error″ approach in finding optimal kinetically unstable morphologies. An alternative approach assumes the utilization of complex polymer architectures, such as donor–acceptor block copolymers. Because of a covalent preorganization of the donor and acceptor components, these materials may form desirable morphologies at thermodynamic equilibrium. This chapter reviews synthetic approaches to such architectures and shows the first photovoltaic results. [ABSTRACT FROM AUTHOR]

A comprehensive outdoor study of polymer solar cells and modules for duration of one year was conducted. Different sample geometries and encapsulations were employed in order to study the spread in the lifetimes. The study is a complimentary report to previous work that focused on indoor ageing tests. Comparison of the indoor and outdoor lifetimes was performed by means of the o-diagram, which constitutes the initial steps towards establishing a method for predicting the lifetime of an organic photovoltaic device under real operational conditions based on a selection of accelerated indoor tests. Acceleration factors were determined using the ISOS-protocols, which enabled reproducible data acquisition between different laboratories and operators within the OPV community. A semi-automatic filtering method was employed for processing data acquired in outdoor tests. It was found that the lifetime of the samples tested under outdoor conditions was somewhere between the lifetimes of samples measured in accelerated indoor test conditions of damp heat and light soaking (ISOS-D-3 and ISOS-L-2) and in moderate indoor test conditions (shelf life and high temperature storage). The presented results reveal that while the accelerated ageing studies reveal days and weeks of lifetime for the studied samples, in outdoor real operational conditions the samples demonstrate stability up to months and seasons. [ABSTRACT FROM AUTHOR]

The presented work addresses the issue of lifetime prediction and intercomparison for organic photovoltaic (OPV) devices tested under different environmental conditions according to ISOS guidelines proposed recently at the International Summit on Organic Photovoltaic Stability. The studies employed P3HT:PCBM based devices produced with different architectures and methods ranging from spin coating to roll-to-roll manufacturing. The purpose of the chosen diversity was to establish the possible spread in the ageing rates generated by different architectures. A logarithmic lifetime diagram associated with the common time units was used for presenting the ageing data, which regardless of the spread in the lifetimes allowed categorizing the level of the stability of P3HT:PCBM based devices tested under different ageing conditions. Moreover, the approach also allowed for estimating the acceleration factors between the moderate and harsh ISOS test conditions employed in the study, as well as identifying the level of improvement of the device stability after encapsulation. The effects of different device architectures and encapsulation techniques on ageing rates of the samples were also studied. This report presents the early steps towards establishing a prediction tool for identifying the lifetime of OPV devices under operational conditions based on the tests under harsh (accelerated) conditions. [ABSTRACT FROM AUTHOR]

A new type of light beam‐induced current 2D mapping system is developed that speeds up acquisition time from hours and days to minutes or even seconds. It is particularly relevant as a tool to characterize printed, large‐scale, organic photovoltaics. Defects inherent to the multi‐layer printing or degradation effects that develop later can be detected with a spatial resolution of <100 μm. It can be used as an in‐line characterization element in the roll‐to‐roll production of organic photovolatics. Several types of electrical connection schemes are developed, including methods suited for continuous web transport. One particularly exciting development is contactless connection through capacitive coupling, which is especially suited for fast roll‐to‐roll characterization of organic photovoltaic modules during the process where electrodes might not be accessible for making a physical electrical contact. Another variation of the technique allows for the extraction of solar cell parameters such as the capacitive time constant, capacitance, and shunt‐ and series resistance at every position (pixel) in the device, which allows new types of 2D mapping that bring out variations and defects in solar cells that are complementary to standard LBIC. It for instance becomes possible to distinguish a short from an open circuit. [ABSTRACT FROM AUTHOR]

Abstract: The polymer and organic solar cell technology is critically presented in the context of other thin film technologies with a specific focus on what it will take to make them a commercial success. The academic success of polymer and organic solar cells far outweigh any other solar cell technology when judging by the number of scientific publications whereas the application of polymer and organic solar cells in real products is completely lacking. This aspect is viewed as a sign of the polymer and organic solar cell field as being more complex and less mature and it raises the question of whether an organic analog to a successful inorganic technology is forcibly needed and indeed whether it is at all worth exploring beyond academia. [Copyright &y& Elsevier]

Abstract: A simple and low cost thin film solution processing system comprising a single roll coating machine has been developed to allow direct investigation of variable parameter effects in roll-to-roll processing. We present roll coating of the active layers in polymer solar cells and validate the instrument by reinvestigating the well known effect of solvent on performance. We obtained a maximum power conversion efficiency of 1.6% for the reference cells, which compares well with reported roll-to-roll coated cells according to ProcessOne, with a relative deviation caused by solvent type nearing 40% on roll coated cells, confirming the solvent to have a significant influence on the performance of the finished cell. We further present a slot-die coating head with an ultra low dead volume allowing for the preparation of roll coated polymer solar cells on flexible substrates with nearly no loss of solution, enabling roll coating testing of new polymers where only small amounts are often available. We demonstrate the formation of >50 solar cells (each with an active area of 1cm2) with printed metal back electrodes using as little as 0.1mL of active layer solution. This approach outperforms spin coating with respect to temperature control, ink usage, speed and is directly compatible with industrial processing and upscaling. [Copyright &y& Elsevier]

Abstract: We applied complementary imaging methods to investigate processing failures of roll-to-roll solution processed polymer solar modules based on polymer:fullerene bulk heterojunctions. For investigation of processing deficiencies in solar modules we employed dark lock-in thermography (DLIT), electroluminescence (ELI) and photoluminescence/reflection imaging (PLI/RI) complemented by optical imaging (OI). The combination of all high resolution images allowed us to allocate the origin of processing errors to a specific deposition process, i.e. the insufficient coverage of an electrode interlayer. The investigation can be divided into a fast DLIT overview of the module and a successive more detailed analysis of the suspicious region by all imaging methods. [Copyright &y& Elsevier]

Abstract: The performance of printable metal back electrodes for polymer solar cells were investigated using light beam induced current (LBIC) mapping of the final solar cell device after preparation to identify the causes of poor performance. Three different types of silver based printable metal inks were employed. Organic solvent based, UV-curable and water based silver inks were tested. Both grid electrodes and full electrodes were employed and it was shown via the grid electrode that the organic solvent based ink adversely affects the device performance under the printed metal whereas both the UV-curable and the water based inks were neutral to improving device performance. Complete roll-to-roll (R2R) processed modules were also tested and some limitations of the LBIC technique was identified for serially connected modules. [Copyright &y& Elsevier]

Controlling the size of the oligomer and introducing functional groups at the ends of the oligomer that allow it to react with separate electrodes are critical issues when preparing materials for molecular wires. We demonstrate a general synthetic approach to oligophenylenevinylene (OPV) derivative molecules with a molecular length up to 9-10 nm which allow for the introduction of aromatic thioacetate functionality in fully conjugated oligomer systems. Oligomers containing 3-15 phenyl units were synthesized by step wise Horner-Wadsworth-Emmons (HWE) reactions of a bifunctional OPV-monomer, which demonstrated good control of the size of the OPVs. Workup after each reaction step ensures a high purity of the final products. End group functionalization was introduced as a last step. [ABSTRACT FROM AUTHOR]

Abstract: A round robin for the performance of roll-to-roll coated flexible large-area polymer solar-cell modules involving 18 different laboratories in Northern America, Europe and Middle East is presented. The study involved the performance measurement of the devices at one location (Risø DTU) followed by transportation to a participating laboratory for performance measurement and return to the starting location (Risø DTU) for re-measurement of the performance. It was found possible to package polymer solar-cell modules using a flexible plastic barrier material in such a manner that degradation of the devices played a relatively small role in the experiment that has taken place over 4 months. The method of transportation followed both air-mail and surface-mail paths. [Copyright &y& Elsevier]

Abstract: A roll-to-roll process for polymer solar cells that does not involve indium-tin-oxide (ITO) is presented. A commercially available kapton foil with an overlayer of copper was used as the substrate. Sputtering of titanium metal onto the kapton/copper in an R2R vacuum process gave the monolithic substrate and back electrode for the devices. The active layer was slot-die coated onto the kapton/Cu/Ti foil followed by slot-die coating of a layer of PEDOT:PSS. No patterning of the first four layers was necessary and only the final front electrode required a pattern. The front electrode was applied by screen printing a protective layer in the areas for front electrode contacts and finally a silver grid was applied by screen printing. The topology of the device and the choice of final grid electrode geometry allowed for serial connection of the individual cells into modules. The individual cells were as large as 150×150mm. The geometric fill factors were as high as 74% and thus much higher than is readily achieved using serially connected cells on the same substrate. [Copyright &y& Elsevier]

Abstract: A roll-to-roll process enabling fabrication of polymer solar cells comprising five layers on flexible substrates is presented. The device geometry is inverted and allow for fabrication on both transparent and non-transparent flexible substrates. The process is illustrated in this work by formation of a bottom electrode comprising silver nanoparticles on a 130 micron thick polyethyleneternaphthalate (PEN) substrate. Subsequently an electron transporting layer of zinc oxide nanoparticles was applied from solution followed by an active layer of P3HT-PCBM and a hole transporting layer of PEDOT:PSS. These first four layers were applied by slot-die coating. The final electrode was applied by screen printing a grid structure that allowed for transmission of 80% of the light. The materials were patterned into stripes allowing for formation of a single cell device and serially connected modules comprising 2, 3 and 8 stripes. All five layers in the device were processed from solution in air and no vacuum steps were employed. An additional advantage is that the use of indium-tin-oxide (ITO) is avoided in this process. The devices were tested under simulated sunlight (1000Wm−2, AM1.5G) and gave a typical performance 0.3% in terms of power conversion efficiency (PCE) for the active layer. The low PCE was due to poor transmission of light through the back electrode. [Copyright &y& Elsevier]

Abstract: Pad printing as a technique for preparing the active layer in polymer solar cells is presented. The technique employs a silicone rubber stamp to pick up the motif from a gravure plate and transfer it to the substrate. The strengths and limitations of pad printing are discussed and polymer solar cells prepared by pad printing are presented. Devices were prepared on indium tin oxide substrates but in principle the entire photovoltaic device comprising front and back electrodes, barrier layers and active layer could be printed with no need for vacuum steps. The device geometry comprises a spin coated transparent zinc oxide front electrode, a pad printed active layer based on a bulk heterojunction of the thermocleavable polymer poly(3-(2-methylhexyloxycarbonyl)thiophene-co-thiopene) (P3MHOCT) and zinc oxide nanoparticles, spin coated PEDOT:PSS and finally a manually cast thermally cured silver paste back electrode. The P3MHOCT was converted to poly(3-carboxy-dithiophene) (P3CT) in situ by heating the film to for a brief period. The entire printing and device preparation was carried out in the ambient atmosphere and the devices obtained had a good stability in air during storage and operation. [Copyright &y& Elsevier]

Abstract: A complete polymer solar cell module prepared in the ambient atmosphere using all-solution processing with no vacuum steps and full roll-to-roll (R2R) processing is presented. The modules comprise five layers that were prepared on a 175-μm flexible polyethyleneterephthalate (PET) substrate with an 80-nm layer of transparent conducting indium–tin oxide (ITO). The ITO layer was first patterned by screen printing an etch resist followed by etching. The second layer was applied by either knife-over-edge (KOE) coating or slot-die coating a solution of zinc oxide nanoparticles (ZnO-nps) followed by curing. The second layer comprised a mixture of the thermocleavable poly-(3-(2-methylhexan-2-yl)-oxy-carbonyldithiophene) (P3MHOCT) and ZnO-nps and was applied by a modified slot-die coating procedure, enabling slow coating speeds with low viscosity and low surface tension ink solutions. The third layer was patterned into stripes and juxtaposed with the ITO layer. The fourth layer comprised screen-printed or slot-die-coated PEDOT:PSS and the fifth and the final layer comprised a screen-printed or slot-die-coated silver electrode. The final module dimensions were 28cm×32cm and presented four individual solar cell modules: a single-stripe cell, a two-stripe serially connected module, a three-stripe serially connected module and finally an eight-stripe serially connected module. The length of the individual stripes was 25cm and the width was 0.9cm. With overlaps of the individual layers this gave a width of the active layer of 0.6cm and an active area for each stripe of 15cm2. The performance was increased ten fold compared to mass-produced modules employing screen printing for all five layers of the device. The processing speeds employed for the R2R processed layers were in the range of 40–50mh−1. Finally a comparison is made with the state of the art represented by P3HT–PCBM as the active layer and full R2R solution processing using slot-die coating. [Copyright &y& Elsevier]

Abstract: A complete polymer solar cell module prepared in the ambient atmosphere under industrial conditions is presented. The versatility of the polymer solar cell technology is demonstrated through the use of abstract forms for the active area, a flexible substrate, processing entirely from solution, complete processing in air using commonly available screen printing, and finally, simple mechanical encapsulation using a flexible packaging material and electrical contacting post-production using crimped contacts. We detail the production of more than 2000 modules in one production run and show that the production technique is scalable and well suited for direct transfer to the printing industry employing existing production equipment. The production speed and cost analysis for the individual modules from this batch is discussed and a forecast for the high volume cost based on this method is given. Further, the points where significant cost reductions can be achieved are identified. The use of the solar cell as the power supply for a small radio and other small electronic circuits is demonstrated. Lastly, the operational stability under ambient conditions in the dark and under illumination is discussed. [Copyright &y& Elsevier]

Abstract: Polymer solar cells are reviewed in the context of the processing techniques leading to complete devices. A distinction is made between the film-forming techniques that are used currently such as spincoating, doctor blading and casting and the, from a processing point of view, more desirable film-forming techniques such as slot-die coating, gravure coating, knife-over-edge coating, off-set coating, spray coating and printing techniques such as ink jet printing, pad printing and screen printing. The former are used almost exclusively and are not suited for high-volume production whereas the latter are highly suited, but little explored in the context of polymer solar cells. A further distinction is made between printing and coating when a film is formed. The entire process leading to polymer solar cells is broken down into the individual steps and the available techniques and materials for each step are described with focus on the particular advantages and disadvantages associated with each case. [Copyright &y& Elsevier]

Abstract: A polymer solar cell that can be stored under ambient conditions (25°C and 35±5% relative humidity) in the dark for 6 months without noticeable degradation in performance is presented. The active layer is based on low-cost materials and is free from fullerenes. No vacuum steps are required for processing the device that employs an inverted device geometry, where the active layers in the device comprise a transparent cathode based on solution processed zinc oxide, an active layer based on a bulk heterojunction of zinc oxide nanoparticles and poly-(3-carboxydithiophene) (P3CT), a PEDOT:PSS layer and finally a printed silver based anode. No encapsulation was employed and the devices were robust and not sensitive to mechanical handling of the active layer and back electrode. The accelerated lifetime in air defined as 80% of the initial performance at continuous illumination (1000Wm−2, AM1.5G, 72±2°C, ambient atmosphere, 35±5% humidity) was typically 100h and the devices were tested for 150h. When keeping the same conditions and lowering the temperature, stable operation for hundreds of hours was possible. In terms of long-term stability, this performance is inferior to inorganic photovoltaics but the technology compares well and competes with small batteries in terms of capacity. The device efficiency more than doubled upon decreasing the incident light intensity from 1000 to 100Wm−2. [Copyright &y& Elsevier]

Abstract: Homopolymer photovoltaic devices based on thin films of polybithiophene, prepared by direct electrodeposition onto transparent fluorine-doped tin oxide electrodes followed by evaporation of an aluminium electrode to complete the device, were reported by Leguenza et al. [J. Solid State Electrochem. 11 (2007) 577.] to exhibit very high open-circuit voltages (V oc) of up to 2V at a very low light intensity of 6.6Wm−2. In this letter, we report our attempts to reproduce the results. We achieved V oc''s⩽0.8V under a light intensity of 23Wm−2. We also observed an unexpected V oc in the dark suggesting that the high voltages previously reported might be attributed to the polarization of the polybithiophene layer, which lead to a battery effect in the dark and therefore not entirely a photovoltaic effect. We conclude that more work is needed before this observation can conceivably be applied in organic photovoltaics. Most notably, the application of this polarization effect depends on the demonstration of the high V oc under high luminous intensities (i.e. >200Wm−2) and at high current densities (>1mAcm−2) which has not been achieved yet. [Copyright &y& Elsevier]

Abstract: In this paper we present the realization of extremely thin absorber (ETA) solar cells employing conductive glass substrates functionalized with TiO2 microstructures produced by embossing. Nanocrystalline or compact TiO2 films on Indium doped tin oxide (ITO) glass substrates were embossed by pressing a silicon stamp containing a μm size raised grid structure into the TiO2 by use of a hydraulic press (1ton/50cm2). The performance of these microstructured substrates in a ETA cell sensitized by a thermally evaporated or chemical bath deposited PbS film and completed by a PEDOT:PSS hole conductor layer and a Au counter electrode is compared to that of planar substrates. Surprisingly planar films produced better performance than micro-structured films. A simple model implying photoconductive shunting paths revealed by junction breakdown at negative bias under illumination is presented. [Copyright &y& Elsevier]

Abstract: Low band gap polymer materials and their application in organic photovoltaics (OPV) are reviewed. We detail the synthetic approaches to low band gap polymer materials starting from the early methodologies employing quinoid homopolymer structures to the current state of the art that relies on alternating copolymers of donor and acceptor groups where strategies for band gap design are possible. Current challenges for OPV such as chemical stability and energy level alignment are discussed. We finally provide a compilation of the most studied classes of low band gap materials and the results obtained in photovoltaic applications and give a tabular overview of rarely applied materials. [Copyright &y& Elsevier]

Abstract: Preliminary data on the fabrication of 0.1m2 polymer solar cells are presented. The process employed screen-printing of an active layer onto an indium-tin-oxide (ITO) electrode pattern (50Ωsquare−1) on a 200μm polyethyleneterphthalate (PET) substrate. After the printing, vacuum coating of an optional layer of C60 and the final aluminium electrode was employed to complete the device. The active layer consisted of poly-1,4-(2-methoxy-5-ethylhexyloxy)phenylenevinylene (MEH-PPV). Chlorobenzene was used as solvent for the screen-printing process. The design of the solar cell module was chosen to employ both serial and parallel connection of individual solar cells. Thirteen individual solar cells with an active area of 7.2cm2 were thus connected in series. The serial connection was chosen to reduce the current density for the large area employed. A step up in voltage is thus preferable to avoid resistive loss. The parallel connection of seven such rows through a screen-printed silver bus gave a solar cell module measuring 40cm×25cm (0.1m2). The active area was 65% of the total area. The remaining 35% of the area was used for interconnections between cells and for the separation between rows. The 65% active area was chosen to encompass a good margin for prototyping/research and to keep contact resistances between the cells low. In a fully automated process the active area could perhaps reach 90–99% interval but problems with current extraction and interconnections were found to become very critical. There are obvious shortcomings to this approach but the advantage of low current density is believed to be the biggest problem in efficient energy extraction from the module when no simple method for reducing the sheet resistance is available. In the simple geometry ITO/MEH-PPV/aluminium the module gave an open circuit voltage (V oc) of 10.5V, a short circuit current (I sc) of 5μA, a fill factor (FF) of 13% and an efficiency (η) of 0.00001% under AM1.5 illumination with an incident light intensity of 1000Wm−2. A geometry employing a sublimed layer of C60 (ITO/MEH-PPV/C60/Al) improved V oc, I sc, FF and η to 3.6V, 178μA, 19% and 0.0002%, respectively. The lifetimes (τ ½) of the devices defined as the time it takes for the module efficiency to attain half of its maximum value were found to improve significantly when a sublimed layer of C60 was included between the polymer and the aluminium electrode. The modules were laminated with 200μm polyethyleneterephthalate (PET) foil to mechanically protect the cells. τ ½ values of 150h were typically obtained. This short lifetime is linked to reaction between the reactive metal electrode (aluminium) and the constituents of the active layer. The modules were tested outdoors in different weather condition (wind, high temperature excursion, rain, snow). Tested during a storm the polymer photovoltaic laminate was subject to vibration stress and deformation and delamination in the organic layer was observed with fast bleaching of the active material. Efficient encapsulation with barriers that has very low oxygen and water permeabilities will be needed before future commercialisation can be anticipated. [Copyright &y& Elsevier]

Abstract: A simple and efficient method for the encapsulation of polymer and organic photovoltaic prototypes is presented. The method employs device preparation on glass substrates with subsequent sealing using glass fiber reinforced thermosetting epoxy (prepreg) against a back plate. The method allows for transporting oxygen and water sensitive devices outside a glove box environment after sealing and enables sharing of devices between research groups such that efficiency and stability can be evaluated in different laboratories. [Copyright &y& Elsevier]

Abstract: Performance improvement of hybrid solar cells (HSC) applying five different thin film semiconductor oxides has been observed during long-time irradiation in ambient atmosphere. This behavior shows a direct relation between HSC and oxygen content from the environment. Photovoltaic devices were prepared as bi-layers of thin film semiconducting oxides (TiO2, Nb2O5, ZnO, CeO2–TiO2 and CeO2) and the polymer MEH-PPV, with a final device configuration of ITO/Oxidethin film/MEH-PPV/Ag. The oxides were prepared as thin transparent films from sol–gel solutions. The photovoltaic cells were studied in ambient atmosphere by recording the initial values of open circuit voltage (V oc) and current density (I sc). Solar decay curves presented as the measurement of the short circuit current as a function of time, IV curves and photophysical analyses were also carried out for each type of device. Solar cells with TiO2 thin films showed the best performance with maximum V oc as high as −0.74V and I sc of 0.4mA/cm2. Solar decay analyses showed that the devices require a stabilization period of several hours in order to reach maximum performance. In the case of TiO2, Nb2O5 and CeO2–TiO2, the maximum current density was observed after 15h; for CeO2, the maximum performance was observed after 30h. The only exception was observed with devices applying ZnO in which the current density decreased drastically and degraded the polymer in just a couple of hours. [Copyright &y& Elsevier]

Abstract: New carboxy-terpyridines selectively functionalized at the 4-, 4′- and 4″-positions were prepared in a three-step procedure with good yields using the Kröhnke reaction followed by saponification. Their complexation with ruthenium led to symmetric and unsymmetric terpyridinyl zwitterionic complexes. [Copyright &y& Elsevier]

Abstract: The incorporation of polymer photovoltaics into textiles was demonstrated following two different strategies. Simple incorporation of a polyethyleneterphthalate (PET) substrate carrying the polymer photovoltaic device prepared by a doctor blade technique necessitated the use of the photovoltaic device as a structural element. The total area of the device on PET was typically much smaller than the active area due to the decorative design of the aluminium electrode. Elaborate integration of the photovoltaic device into the textile material involved the lamination of a polyethylene (PE) film onto a suitably transparent textile material that was used as substrate. Plasma treatment of the PE-surface allowed the application of a PEDOT electrode that exhibited good adherence. Screen printing of a designed pattern of poly 1,4-(2-methoxy-5-(2-ethylhexyloxy))phenylenevinylene (MEH-PPV) from chlorobenzene solution and final evaporation of an aluminium electrode completed the device. The total area of the textile device was 1000cm2 (25cm×40cm) while the active area (190cm2) was considerably smaller due to the decorative choice of the active material. [Copyright &y& Elsevier]

Abstract: The lifetimes of organic photovoltaic cells based on conjugated polymer materials were studied. The device geometry was glass:ITO:PEDOT:PSS:C12-PSV:C60:aluminium. To characterise and elucidate the parts of the degradation mechanisms induced by molecular oxygen, 18O2 isotopic labelling was employed in conjunction with time-of-flight secondary ion mass spectrometry. A comparison was made between devices being kept in the dark and devices that had been subjected to illumination under simulated sunlight (1000Wm−2, AM1.5) and this demonstrated that oxygen-containing species were generated throughout the active layer with the largest concentration towards the aluminium electrode. For devices that had been kept in the dark oxygen species were only observed at the immediate interface between the aluminium and the organic layer. The isotopic labelling allowed us to demonstrate that the oxygen comes from the atmosphere and diffuses through the aluminium electrode and into the device. [Copyright &y& Elsevier]

Abstract: Transparent electrodes based on PEDOT were prepared using a variety of techniques suitable for large area applications from 3,4-ethylenedioxythiophene (EDT) and Fe(III)-tosylate. High conductivities were obtained (∼20Ω−1) with moderate transmission in the UV-visible range 350–600nm. We subsequently demonstrate the application of PEDOT electrodes to flexible polyethyleneterphthalate plastic substrates (PET) prepared by this procedure for polymer photovoltaic devices with active areas of 4.2cm2 using a 1:4 w/w mixture of MEHPPV and PCBM. We obtain typical efficiencies of 0.2% under simulated sunlight (AM1.5 at 1000Wm−2). [Copyright &y& Elsevier]

Abstract: The synthesis of a zwitterionic ruthenium dye that binds to anatase surfaces and has a built-in functionality that allows for the attachment of a conjugated polymer chain is presented. The system was found to adsorb on the surface of anatase anchored by the ruthenium dye. Two types of devices were prepared: standard photoelectrochemical (PEC) solar cells and polymer solar cells. The PEC solar cells employed a sandwich geometry between TiO2 nanoporous photoanodes and Pt counter electrodes using LiI/I2 in CH3CN as an electrolyte. The polymer solar cells employed planar anatase electrodes and the complex was adsorbed onto the surface before evaporation of gold electrodes. Alternative devices were obtained by spincoating of the polymer solution onto PEDOT:PSS covered indium-doped tin oxide substrates. PEC solar cells gave the best results and the main finding was that the polymer chain served as a light harvesting antenna for the ruthenium dye. [Copyright &y& Elsevier]

Abstract: We present the synthesis of oligohexylthiophenes starting from 3, 4′-dihexyl-[2, 2′]bithiophene (1) 3, 4′, 4″, 4‴-tetrahexyl-[2, 2′; 5′, 2″; 5″, 2‴]quarterthiophene (2), 3, 4′, 4″, 4‴, 4⁗, 4′′′′′, 4′′′′′′, 4′′′′′′′-octahexyl-[2, 2′; 5′, 2″; 5″, 2‴; 5‴, 2⁗; 5⁗, 2′′′′′; 5′′′′′, 2′′′′′′; 5′′′′′′, 2′′′′′′′]octithiophene (3) and 3, 4′, 4″, 4‴, 4⁗, 4′′′′′, 4′′′′′′, 4′′′′′′′, 4′′′′′′′′, 4′′′′′′′′′, 4′′′′′′′′′′, 4′′′′′′′′′′′, 4′′′′′′′′′′′′, 4′′′′′′′′′′′′′, 4′′′′′′′′′′′′′′, 4′′′′′′′′′′′′′′′-hexadecahexyl-[2, 2′; 5′, 2″; 5″, 2‴; 5‴, 2⁗; 5⁗, 2′′′′′; 5′′′′′, 2′′′′′′; 5′′′′′′, 2′′′′′′′; 5′′′′′′′, 2′′′′′′′′; 5′′′′′′′′, 2′′′′′′′′′; 5′′′′′′′′′, 2′′′′′′′′′′; 5′′′′′′′′′′, 2′′′′′′′′′′′; 5′′′′′′′′′′′, 2′′′′′′′′′′′′; 5′′′′′′′′′′′′, 2′′′′′′′′′′′′′; 5′′′′′′′′′′′′′, 2′′′′′′′′′′′′′′; 5′′′′′′′′′′′′′′, 2′′′′′′′′′′′′′′′]hexadecathiophene (4) by regioselective bromination using N-bromosuccinimide and regioselective lithiation using lithiumdiisopropylamide in ethylbenzene/THF/heptane followed by reaction with trimethylstannylchloride and subsequent palladium catalysed Stille coupling. We further synthesised 5,15-bis(3, 4′, 4″, 4‴, 4⁗, 4′′′′′, 4′′′′′′, 4′′′′′′′-octahexyl-[2, 2′; 5′, 2″; 5″, 2‴; 5‴, 2⁗; 5⁗, 2′′′′′; 5′′′′′, 2′′′′′′; 5′′′′′′, 2′′′′′′′]octithiophene-5-yl)-10, 20-bis(3, 5-ditertbutylphenyl)zinc(II)porphyrin (5) from trimethyl(3, 4′, 4″, 4‴, 4⁗, 4′′′′′, 4′′′′′′, 4′′′′′′′-Octahexyl-[2, 2′; 5′, 2″; 5″; 2‴; 5‴, 2⁗; 5⁗, 2′′′′′; 5′′′′′, 2′′′′′′; 5′′′′′′, 2′′′′′′′]octithiophene-5-yl)stannane (3-SnMe3 ) and 5, 15-dibromo-10, 20-bis(3, 5-ditertbutylphenyl)zinc(II)porphyrin (6) by Stille coupling. All the products were characterised by size exclusion chromatography (SEC), NMR, MALDI-TOF and elemental analysis and purified by preparative SEC before subjecting them to photophysical studies. UV–vis and emission spectroscopy were used to determine quantum yields and energy transfer. The photon balance was established and used to rationalise the photovoltaic behaviour of 4 and 5. While 4 gave rise to photovoltaic devices giving a moderate photovoltaic response that was symbatic with the absorption spectrum, 5 showed a photovoltaic response that was antibatic with a part of the absorption spectrum of the zinc-porphyrin constituent. We ascribe this behaviour to efficient internal conversion of the energy absorbed by (and the energy transferred to) the zinc-porphyrin constituent. [Copyright &y& Elsevier]

Abstract: Herein, we discuss the analyses and quantification of the different components in porphyrin mixtures, prepared from p-anisaldehyde, p-tolualdehyde, and 5-(4-bromophenyl)-dipyrromethane with acid catalysis, using NMR and HPLC. The advantages and disadvantages of these analytical methods are emphasized. Due to the similar size of a bromine atom and a methyl group it was possible to grow crystals suitable for X-ray crystallographic studies from a mixture of porphyrins, where the 4-position of the meso-phenyl rings was either substituted with methyl groups or bromine atoms. We also show that X-ray studies are inferior to NMR analysis for determining the components in a porphyrin mixture. [Copyright &y& Elsevier]

Four new monomers for directional stepwise synthesis of oligophenylenevinylenes (OPVs) (4-{2-[4-(5,5-dimethyl[1,3]dioxan-2-yl)-2,5-dipropoxyphenyl]vinyl}benzyl)phosphonic acid diethyl ester, (5-{2-[4-(5,5-dimethyl[1,3]dioxan-2-y])-2,5-dipropylphenyl]vinyl}thiophene-2-ylmethyl)phosphonic acid diethyl ester, (5-{2-[4-{5,5-dimethyl[1,3]dioxan-2-yl)-2,5-diprepoxyphenyl]vinyl}thiophene-2-ylmethyl)phosphonic add diethyl ester, and (7-{2-[4-(5,5-limethyl[1,3] dioxan-2-yl)z2,5-dipropylphenyl]-vinyl}benzo[1,2,5]thiadiazol-4-ylmethyl)phosphonic acid diethyl ester have been prepared. Trimeric OPVs were then synthesized and tested as active materials in photovoltaic cells. Conversion efficiencies in the range of 0.5–1% were obtained in blends with the soluble C60 derivative PCBM. A terpyridine end-functionalized trimer and a heterotrimer with a mixed composition of monomers were also prepared. [ABSTRACT FROM AUTHOR]

Abstract: Large area polymer photovoltaic cells based on poly[(2-methoxy-5-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) were prepared. The lifetimes of the photovoltaic cells were studied in terms of the atmosphere, handling, electrode treatment, mode of preparation and barrier layers by recording the short circuit current as a function of time. Two exponential fits to the decay curves allowed for the extraction of the time constants for different degradation processes. For the periods of time studied here (24–300h), the decay curves could be fitted with two exponential functions. Common to the preparations were that the first half-life remained short and was independent of the presence of oxygen. When fullerenes were employed by sublimation of a layer of C60 or as the soluble PCBM, the first half-life was an order of magnitude longer and depended on the presence of oxygen. By employing different barrier layers, we found the first half-life to be linked to the aluminium polymer interface and ascribe it to a photochemical reaction between the organic material and the reactive aluminium at the interface. The second and longer half-life was found to depend on the presence of oxygen. We also discuss our findings of the short lifetimes for organic photovoltaics under AM1.5 illumination in the context of future applications. [Copyright &y& Elsevier]

Abstract: The principle of photobleaching in the conjugated polymer material didodecylstilbenevinylene (didodecyl-PSV) was used as a built-in photoresist property to control the extent of the emissive layer in polymer light emitting devices (PLEDs). Illumination of thin films of the conjugated polymer material on optically transparent conducting substrates through a positive mask with short exposure times (20–60s) using a 150W Xenon lamp and subsequent application of the and the second electrode enabled the formation of an electroluminescent image of the mask. We demonstrate a direct method where no photoresist, intermediate steps or mechanical manipulation is required to generate a complex emissive pattern employing a homogenous film and homogenous electrodes. The fluorescence of the film showed complex lifetime decays. We found that the lifetime increased with emission wavelength indicating the presence of energetically disordered excitons. The fine structure observed in the solution emission is absent in the film emission. However, after photobleaching the film emission becomes very similar to the solution emission. The appearance of fine structure could indicate that only one state became responsible for the photoluminescence spectrum. Infrared spectroscopy was used to confirm the presence of a degradation route similar to that reported for dialkoxypolyphenylenevinylene materials where the vinylene bonds are react with molecular oxygen and form carboxylic acid groups. Finally the effect of using different electrode metals was established and a comparison made between the photoluminescence and electroluminescence properties. The electroluminescence emission maximum (580nm) of didodecyl-PSV light emitting devices was found to be redshifted by 20nm compared to the photoluminescence, exhibited turn-on voltages below 3V and reached a luminance of 100cdm−2 at current densities below 10mAcm−2. [Copyright &y& Elsevier]

A new stepwise directional synthetic route to single-oligomer p-phenylenevinylenes (OPVs) has been developed. The first step in the reaction sequence is the condensation of a functionalized benzaldehyde with a novel monomer having a methyl phosphonate ester group in one end and an acetal-protected aldehyde at the other end of a stilbene core. Oligomerization then proceeds stepwise by alternating reaction of the previous aldehyde-terminated OPV fragment with the monomer and deprotection of the acetal. Thus, a series of OPVs with 3, 5, 7, 9, and 11 phenylene vinylene units has been prepared that has an electron-donating methoxy group at one end and an electron-accepting aldehyde group at the other end. Some examples where a dimethylamino group replaced the methoxy group were also prepared. The oligomer with seven phenylene vinylene units was then further derivatized at the aldehyde position to create a series of OPVs with a range of substituents from strongly electron-accepting nitrophenyl to electron-donating methoxyphenyl. Photovoltaic cells were assembled with the synthesized OPVs as the photoactive layer. Illumination under simulated sunlight (AM1.5) gave short circuit currents (Isc) in the range 0.015-0.5 mA cm-2 and typical open circuit voltages (Voc) of 0.4-0.8 V. The maximum efficiency obtained was ∼0.1%. [ABSTRACT FROM AUTHOR]

A synthetic approach to the synthesis of a large super molecule composed of two chemically different conducting polymer blocks with, respectively, high and low lying electronic energy levels linked through a porphyrin dye molecule is presented. The synthetic strategies to these molecular architectures are discussed. Finally the molecular systems are applied to make photovoltaic devices and the rather low efficiency is discussed in terms of the synthetic approach. [Copyright &y& Elsevier]

The possibility of making large area (100 cm2) polymer solar cells based on the conjugated polymer poly 1,4-(2-methoxy-5-ethylhexyloxy)phenylenevinylene (MEH-PPV) was demonstrated. Devices were prepared by etching an electrode pattern on ITO covered polyethyleneterephthalate (PET) substrates. A pattern of conducting silver epoxy allowing for electrical contacts to the device was silk screen printed and hardened. Subsequently a pattern of MEH-PPV was silk screen printed in registry with the ITO electrode pattern on top of the substrate. Final evaporation of an aluminum electrode or sublimation of a Buckminsterfullerene (C60) layer followed by an aluminum electrode completed the device. The typical efficiency of the prototype devices consisting of three solar cells in series were 0.0046% (under AM1.5 conditions) with open-circuit voltages (Voc) of 0.73 V and short-circuit currents (Isc) of 20 μA cm-2. The half-life based on Isc in air for the devices were 63 h. The cells were laminated in a 125 μm PET encasement. Lamination had a negative effect on the lifetime.We demonstrate the feasibility of industrial production of large area solar cells (1 m2) by silk screen printing and envisage the possibility of production volumes 10000 m2 h-1 at a cost that is on the order of 100 times lower than that of the established monocrystalline silicon solar cells in terms of materials cost. [Copyright &y& Elsevier]

In this paper an overview of the development of organic photovoltaics is given, with emphasis on polymer-based solar cells. The observation of photoconductivity in solid anthracene in the beginning of the 19th century marked the start of this field. The first real investigations of photovoltaic (PV) devices came in the 1950s, where a number of organic dyes, particularly chlorophyll and related compounds, were studied. In the 1980s the first polymers (including poly(sulphur nitride) and polyacetylene) were investigated in PV cells. However, simple PV devices based on dyes or polymers yield limited power conversion efficiencies (PCE), typically well below 0.1%. A major breakthrough came in 1986 when Tang discovered that bringing a donor and an acceptor together in one cell could dramatically increase the PCE to 1%. This concept of heterojunction has since been widely exploited in a number of donor–acceptor cells, including dye/dye, polymer/dye, polymer/polymer and polymer/fullerene blends. Due to the high electron affinity of fullerene, polymer/fullerene blends have been subject to particular investigation during the past decade. Earlier problems in obtaining efficient charge carrier separation have been overcome and PCE of more than 3% have been reported. Different strategies have been used to gain better control over the morphology and further improve efficiency. Among these, covalent attachment of fullerenes to the polymer backbone, creating so-called double-cable polymers, is the latest. The improved PCE of plastic solar cells combined with increased (shelf and operating) lifetime, superior material properties and available manufacturing techniques may push plastic PVs to the market place within a few years. [Copyright &y& Elsevier]

We report a new synthesis of 1,4-diamino-2,5-dioctylbenzene (1) and its application to condensation polymerisation reactions with terephthaldehyde and tetrafluoroterephthaldehyde to give respectively poly-1,1′-(2,5-dioctyl-1,4-phenylene-1′,2′-azomethine-1″,4″-phenylene-2‴,1‴-azomethine) (2) and poly-1,1′-(2,5-dioctyl-1,4-phenylene-1′,2′-azomethine-2″,3″,5″,6″-tetrafluoro-1″,4″-phenylene-2‴,1‴-azomethine) (3). The polymers 2 and 3 were characterised by NMR, SEC, UV-Vis and X-ray powder diffraction. Pulse radiolysis time resolved microwave conductivity (PR-TRMC) was employed for determination of the carrier mobility and carrier lifetimes. [Copyright &y& Elsevier]

Photovoltaic devices based on poly-2′,5′-dioctyl-4,4′′-terphenylenecyanovinylene (J-domain) and 4-aza-4-(4′-(poly-2′,5′-dioctyl-4,4′′-terphenylene-1-cyanovinylene-2-yl)biphen-4-yl)-8,12-dioxa-4,8,12,12c-tetrahydrodibenzo[cd,mn]pyrenium tetrafluoroborate (JA-assembly) were prepared using indiumtinoxide (ITO) as the transparent electrode and aluminium as the second electrode. While the photovoltaic response of the J-domain exhibited low short circuit currents of −0.1 nA cm−2, the corresponding short circuit current of the JA-assembly was observed to be +10 nA cm−2. The 100-fold increase in magnitude was related to the known energy transfer from the J-domain to the A-domain in the JA-assembly, and the inversion of the sign of the photovoltaic response that implies that the electrodes have a reversed polarity was explained on the basis of the positions of the energy levels and involves the action of the A-domain as a blocking layer and a light operated charge pump that efficiently transfers electrons to the ITO electrode. [Copyright &y& Elsevier]

The functionalisation of the hinge region in a molecular tweezer molecule showing a strong binding to explosives is presented. Two versatile functional groups are introduced, a carboxylic acid and a bromine atom. [Copyright &y& Elsevier]

The performance of devices based on conducting polymers is highly dependent on the organization of the polymer chains with respect to the device structure. We present a method to probe the organization of the polymers that makes use of the σ–σ* transitions in alkyl C&z.sbnd;C and C&z.sbnd;H bonds of the conducting polymer poly(3-hexylthiophene) (P3HT). The vacuum ultraviolet (VUV) absorption properties of these transitions are highly anisotropic due to the absorption mechanism where maximum absorption takes place when the bond vector is parallel to the electric field vector of the VUV photons. There are large differences in the VUV absorption spectra in the 120–150 nm range of respectively spincoated and cast films of the polymer. If knowledge of the polymer organization is available by other means, i.e. X-ray diffraction a simple VUV absorption spectrum can be used to determine the orientation of a given sample preparation. [Copyright &y& Elsevier]

The complete description of a high power spectrometer, allowing for large area illumination of up to 10 cm[SUP2] in the wavelength range 200-800 nm with average power densities of 2 mW cm[SUP2], is provided. The setup employs a stationary 150 W xenon lamp used in conjunction with a simple stationary single monochromator grating. The photovoltaic sample under test is placed in a stainless-steel vacuum chamber allowing for operating pressures down to 10[SUP-6] mbar equipped with a quartz window and electrical connections. The entire vacuum chamber was placed on a moving arm allowing for positioning in a selected part of the diffracted beam of the monochromator. The typical spectral resolution was 12 nm cm[SUP-1] which gave bandwidths of 25 nm with a 2 cm sample width. The electrical characteristics of the photovoltaic device under test was measured using a source meter giving an experimental current sensitivity of 10 pA. We finally demonstrate the application of the instrumental setup for the characterization of a polymer based photovoltaic. [ABSTRACT FROM AUTHOR]

We report a new synthesis of a 10,20-diphenyl5,15-bis(4-cyanophenyl)porphyrin (1) and its reduction to give 10,20-diphenyl-5,15-bis(4-formylphenyl)porphyrin (2). When the conducting polymer poly(2',5'-diocty]-4,4'-terphenylenecyanovinylene) was prepared in the presence of 2, we obtained a three-domain structure, compound 3, consisting of two homopolymer blocks (J domains) with the porphyrin dye molecule (P domain) in the middle. The JPJ assembly was subjected to photophysical studies where we showed that the J domain could serve as a light-harvesting antenna for the P domain. [ABSTRACT FROM AUTHOR]

The preparative use of the reaction between tris(2,6-dimethoxyphenyl)carbenium tetrafluoroborate and excess of an arylamine such as 4-methylaniline or 4-bromoaniline to yield firstly the aryl functionalised acridinium derivatives and then further in situ reaction to yield the desired functionalised triangulenium salts was found to be problematic. A preparative route for the triangulenium salts is presented along with a demonstration of the further derivatisation by standard Suzuki coupling reaction. [Copyright &y& Elsevier]

Investigates the effect of perfluorination on photophysical properties of isostructural donor-acceptor-donor dye molecules. Characterization of the molecules; Synthesis of fluorinated benzene compounds; Determination of the X-ray structure.

Examines the role of perdeuterated cryoprotectant on the neutron studies of molecular organic solids. Solution of ephedrine hemihydrate structure; Removal of the macromolecular crystals; Concentration of the cryoprotectant oil.

Examines the preparation of the potentially chiral 7,8-dioxa[6]helicenes through dehydrogenation. Structural properties of the two aromatic helicenes; Use of nuclear magnetic resonance and X-ray crystallization in the study; Structural characterization of the deuterium labeled compound.

Presents a conformational analysis of the calix[4]arenes based on the presentation of crystallographic data in a Ramachandran-type plot and the relation to the unconstrained diphenylmethane system. Comparison with other known [n]cyclophanes; Typical torsion angles for the different conformers of the calix[4]arene skeleton.