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A novel approach to equivalent circuit modelling of organic photovoltaic (OPV) cells capable of simulating both optimal and degraded devices has been developed. Freshly made OPVs (composed of an active layer with a blended poly (3-hexylthiophene) (P3HT) and indene-C60 bisadduct (ICBA) film), that exhibit a characteristic ‘J’ shaped current-voltage (I-V) curve both in the dark and under illumination, are typically fitted to a one-diode equivalent circuit model. However, as device performance deteriorates, the I-V curve undergoes a series of changes resulting in the evolution of an ‘S’ shaped I-V curve, for which there is no widely accepted equivalent circuit model. Here we present a building-block approach to develop a simple equivalent circuit model which provides an excellent fit to experimental I-V data spanning the continuum from the ideal ‘J’ to degraded ‘S’ shaped curves. Applying this new model to P3HT:ICBA devices provides insights into the physical processes that occur during degradation. [ABSTRACT FROM AUTHOR]

Water-based nanoparticulate (NP) and bulk heterojunction (BHJ) organic photovoltaic (OPV) devices based on blends of poly(9,9-dioctylfluorene-co-N,N-bis(4-butylphenyl)-N,Ndiphenyl-1,4-phenylenediamine) (PFB) and poly(9,9-dioctylfluorene-co-benzothiadiazole (F8BT) have been fabricated with aluminium and calcium/aluminium cathodes. The NP devices exhibit power conversion efficiencies (PCEs) that are double that of the corresponding BHJ device. Moreover, the addition of calcium into the cathode structure results in a dramatic increase in open circuit voltage and PCEs approaching 1% for water-based polyfluorene OPV devices. [ABSTRACT FROM AUTHOR]

Abstract: Water-based polymer nanoparticle dispersions offer the prospect of addressing two of the main challenges associated with printing large area organic photovoltaic (OPV) devices; namely how to control the nanoscale architecture of the active layer and eliminate the need for hazardous organic solvents during device fabrication. However, to date, the efficiencies of nanoparticulate-based devices have been inferior to that of the corresponding bulk-heterojunction devices. Here we present an approach for producing optimised OPV devices from polymer nanoparticles via the fabrication of multilayered device architectures. We show that by controlling both nanoparticle morphology and inter-particle interactions it is now possible to build polyfluorene OPV devices from aqueous dispersions of nanoparticles that are more efficient than the corresponding bulk heterojunction devices. In particular we show that: (1) the polyfluorene nanoparticle morphology is suited to effective charge separation, (2) thermal treatment of the deposited layers results in improved interparticle connectivity and effective charge transport, and (3) the optimal device thickness is a delicate balance between the repair of layer defects and the creation of stress cracking in the nanoparticulate film. As such, this work offers insights for the development of printable photovoltaic devices based on water-dispersed nanoparticulate formulations. [Copyright &y& Elsevier]

In order for OPV devices to transition from the laboratory to the industrial scale, accurate measurements of device operating stability and lifetime are crucial. This paper compares the degradation of ITO/PEDOT:PSS/P3HT:ICBA/Ca/Al and ITO/MoO 3 /P3HT:ICBA/Ca/Al devices using the three main ISOS standard testing protocols: (a) ISOS-D-1, (b) ISOS-O-1 and (c) ISOS-L-1. We show that: (1) ITO/MoO 3 /P3HT:ICBA/Ca/Al devices are more stable than their PEDOT counterparts under the ISOS-D-1 protocol, as has been reported previously. (2) Under the ISOS-O-1 protocol, unencapsulated MoO 3 based devices are more stable than the equivalent PEDOT device but, when encapsulated, the degradation rates of the MoO 3 and PEDOT devices are the same. (3) By contrast, when measured under the ISOS-L protocol, the MoO 3 based devices are either equivalent to (unencapsulated devices) or, indeed, actually degrade faster (encapsulated devices) that their PEDOT counterparts. We demonstrate that these differences arise from the dominant degradation mode changing under the different protocols. As such, this paper highlights that the choice of testing protocol significantly influences the reported stability of OPV devices. In particular, the ISOS-D and ISOS-L protocols do not necessary reflect OPV device performance under actual operating conditions and thus stability measurements using these protocols should be treated with caution. [ABSTRACT FROM AUTHOR]

Abstract: Organic photovoltaics (OPVs) are a recent technology that has gained much attention as a potential low cost power source. Despite this promise, there is a lack of published studies that address the likely cost of commercial-scale OPV modules. In this work, an engineering study estimate has been performed to determine the projected cost of mass-manufactured OPV modules. The materials, production capital and operating costs have been calculated and sensitivity analyses performed to determine the parameters of greatest economic influence. Significantly, the model includes a calculation of the costs required to establish bulk manufacturing of the current high cost speciality materials components, encompassing synthesis and associated chemical plant design. The economic modelling reveals that the calculated mass-manufactured OPV module costs are considerably lower than current literature estimates, with OPV modules costed at $7.85 per square metre with an uncertainty of±30%. Total module cost was found to be most sensitive to the plastic substrate prices, while the production rate did not have a significant impact on module cost for rates above~50m2/min. The results highlight the future cost potential of OPV technology and can be used to assist with scale-up planning. [Copyright &y& Elsevier]