A series of modified tetraphenylporphyrins varying only in the electron-donating or electron-withdrawing character of the substituents in the para-phenyl position have been blended into the active layer of MEH-PPV:PCBM bulk heterojunction solar cells. Increasing the electron-withdrawing ability of the substituents, as quantified by the Hammett constant, systematically alters the device efficiency of ternary poly[2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylenevinylene]:porphyrin:[6,6]-phenylC61-butyric acid methyl ester (MEH-PPV:porphyrin:PCBM) bulk heterojunction organic solar cells through alteration of the HOMO/LUMO levels and, thereby, the open-circuit voltage of the cell. We show that the porphyrin concentrates at the MEH-PPV:PCBM interface in these blends and that the devices operate via a cascade mechanism when the highest occupied molecular orbital (HOMO) of the porphyrin is higher in energy that that of MEH-PPV, but via a parallel/alloy device mechanism, when the HOMO of the porphyrin is lower in energy than that of MEH-PPV. As such, this work highlights how the energetics of the ternary component can determine device performance by switching between charge generation models simply by altering the electron-withdrawing character of the porphyrin ternary additive.

Diabetes mellitus is a chronic condition which is approaching epidemic levels globally. Sufferers of diabetes require regular monitoring of their blood glucose levels for successful treatment and the current widely used methods are invasive and painful. There is therefore an urgent need for simple, noninvasive methods of blood glucose concentration monitoring. Saliva is a medium whose glucose concentration correlates well with that of glucose in blood, while readily allowing noninvasive and pain-free sampling. Here, we demonstrate organic enzymatic glucose sensors fabricated at pilot-scale and at low cost, which show high sensitivity to glucose in human saliva for biologically relevant concentrations (up to 0.2 mM) and a limit of detection of 0.029 mM. Additionally, we show that the devices are highly selective for glucose in the presence of key interferents such as ascorbic acid and uric acid.

The prospect of large-scale production of low-cost electronic devices is a driving factor behind the recent interest in printed organic electronics. However, the upscaling of laboratory organic electronic devices is extremely challenging since it requires the adaptation of materials and fabrication processes optimized for the small scale to industrial manufacturing techniques, such as roll-to-roll printing. Here, we demonstrate the fabrication of all-printed organic biosensors at the pilot production scale for use in the detection of glucose. By translating device architecture and operation, as well as electrode design and ink formulations of previously reported laboratory-scale glucose sensors to industrial printing and coating processes, we demonstrate sub-millimolar sensitivity to glucose in fully printed devices in a process which is now scalable to commercial production quantities. This Letter highlights the significant challenges associated with developing upscaled printed organic electronic biosensors and the approaches needed to address them.

The performance of poly(3-hexylthiophene) (P3HT): phenyl-C-61-butyric acid methyl ester (PCBM) organic photovoltaic (OPV) devices was found to be strongly influenced by environmental during preparation, thermal annealing conditions, and the material blend composition. We optimized laboratory fabricated devices for these variables. Humidity during the fabrication process can cause electrode oxidation and photo-oxidation in the active layer of the OPV. Thermal annealing of the device structure modifies the morphology of the active layer, resulting in changes in material domain sizes and percolation pathways which can enhance the performance of devices. Thermal annealing of the blended organic materials in the active layer also leads to the growth of crystalline for P3HT domains due to a more arrangement packing of chains in the polymer. Poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) acts as a hole transport layer in these P3HT:PCBM devices. Two commercially materials of PEDOT:PSS were utilizing in the optimization of the OPV in this research; high conductivity PEDOT:PSS-PH1000 and PEDOT:PSS-Al4083, which is specifically designed for OPV interfaces. It was demonstrated that OPVs were prepared with PEDOT:PSS-PH1000 have a less than the average performance of PEDOT:PSS-Al4083. The power conversion efficiency (PCE) decreased clearly with a reducing in masking area devices from 5 mm(2) to 3.8 mm(2) for OPVs based on PH1000 almost absolutely due to the reduced short circuit current (J(sc)). This work provides a roadmap to understanding P3HT:PCBM OPV performance and outlines the preparation issues which need to be resolved for efficient device fabrication

The fabrication of organic photovoltaics (OPVs) from non-hazardous nanoparticulate (NP) inks offers considerable promise for the development of eco-friendly large-scale printed solar modules. However, the typical NP core-shell morphology (driven by the different donor/acceptor affinities for the surfactant used in NP synthesis) currently hinders the photovoltaic performance. As such, surfactant engineering offers an elegant approach to synthesizing a more optimal intermixed NP morphology and hence an improved photovoltaic performance. In this work, the morphology of conventional sodium dodecyl sulfate (SDS) and 2-(3-thienyl) ethyloxybutylsulfonate (TEBS)-stabilized poly(3-hexylthiophene) (P3HT) donor:phenyl-C61-butyric acid methyl ester (PC61BM) acceptor NPs is probed using scanning transmission X-ray microscopy, UV-vis spectroscopy, grazing-incidence X-ray diffraction, and scanning electron microscopy. While the SDS-stabilized NPs exhibit a size-independent core-shell morphology, this work reveals that TEBS-stabilized NPs deliver an intermixed morphology, the extent of which depends on the particle size. Consequently, by optimizing the TEBS-stabilized NP size and distribution, NP-OPV devices with a power conversion efficiency that is ∼50% higher on average than that of the corresponding SDS-based NP-OPV devices are produced.

This work reports the development of a highly sensitive pressure detector prepared by inkjet printing of electroactive organic semiconducting materials. The pressure sensing is achieved by incorporating a quantum tunnelling composite material composed of graphite nanoparticles in a rubber matrix into the multilayer nanostructure of a printed organic thin film transistor. This printed device was able to convert shock wave inputs rapidly and reproducibly into an inherently amplified electronic output signal. Variation of the organic ink material, solvents, and printing speeds were shown to modulate the multilayer nanostructure of the organic semiconducting and dielectric layers, enabling tuneable optimisation of the transistor response. The optimised printed device exhibits rapid switching from a non-conductive to a conductive state upon application of low pressures whilst operating at very low source-drain voltages (0–5 V), a feature that is often required in applications sensitive to stray electromagnetic signals but is not provided by conventional inorganic transistors and switches. The printed sensor also operates without the need for any gate voltage bias, further reducing the electronics required for operation. The printable low-voltage sensing and signalling system offers a route to simple low-cost assemblies for secure detection of stimuli in highly energetic systems including combustible or chemically sensitive materials.

Sodium tungsten bronze (Na x WO3) is a promising alternative plasmonic material to nanoparticulate gold due to its strong plasmonic resonances in both the visible and near-infrared (NIR) regions. Additional benefits include its simple production either as a bulk or a nanoparticle material at a relatively low cost. In this work, plasmonic Na x WO3 nanoparticles were introduced and mixed into the nanoparticulate zinc oxide electron transport layer of a water processed poly(3-hexylthiophene):phenyl-C61-butyric acid methyl ester (P3HT:PC61BM) nanoparticle (NP) based organic photovoltaic device (NP-OPV). The power conversion efficiency of NP-OPV devices with Na x WO3 NPs added was found to improve by around 35% compared to the control devices, attributed to improved light absorption, resulting in an enhanced short circuit current and fill factor.

A systematic approach for assessing organic photovoltaic (OPV) materials for large scale production based on the efficiency, lifetime and material cost has been developed. A Ω of 2.55 results in the following maximum material cost.

This study reports the scalability of direct arylation polymerization (DArP) batch reactions for the preparation of poly(3-hexylthiophene) (P3HT) using the Herrmann-Beller catalyst combined with a tertiary phosphine in the green solvent 2-methyltetrahydrofuran on scales ranging from 0.5 to 10 g. The physical properties of these DArP polymers are compared to those resulting from P3HT prepared via Grignard metathesis (GRIM) on a 130 g scale. Both DArP and GRIM methods are found to produce highly regioregular polymers with no evidence of beta-defects and the polymers are found to exhibit comparable device performance as donor materials in bulk heterojunction organic solar cells. Purification studies coupled with device measurements highlight the necessity to carefully address the presence of impurities in materials produced from large-scale DArP batch reactions. Economic analyses reveal that the cost involved in the preparation of P3HT via DArP or GRIM procedures are comparable per gram of product and show that the most expensive component is unique for each method.

In this study we have optimised the preparation conditions for large-volume nanoparticle inks, based on poly(3-hexylthiophene) (P3HT):indene-C60 multiadducts (ICxA), through two purification processes: centrifugal and crossflow ultrafiltration. The impact of purification is twofold: firstly, removal of excess sodium dodecyl sulfate (SDS) surfactant from the ink and, secondly, concentration of the photoactive components in the ink. The removal of SDS was studied in detail both by a UV–vis spectroscopy-based method and by surface tension measurements of the nanoparticle ink filtrate; revealing that centrifugal ultrafiltration removed SDS at a higher rate than crossflow ultrafiltration even though a similar filter was applied in both cases (10,000 Da Mw cut-off). The influence of SDS concentration on the aqueous solar nanoparticle (ASNP) inks was investigated by monitoring the surface morphology/topography of the ASNP films using atomic force microscopy (AFM) and scanning electron microscopy (SEM) and photovoltaic device performance as a function of ultrafiltration (decreasing SDS content). The surface morphology/topography showed, as expected, a decreased number of SDS crystallites on the surface of the ASNP film with increased ultrafiltration steps. The device performance revealed distinct peaks in efficiency with ultrafiltration: centrifuge purified inks reached a maximum efficiency at a dilution factor of 7.8 × 104, while crossflow purified inks did not reach a maximum efficiency until a dilution factor of 6.1 × 109. This difference was ascribed to the different wetting properties of the prepared inks and was further corroborated by surface tension measurements of the ASNP inks which revealed that the peak efficiencies for both methods occurred for similar surface tension values of 48.1 and 48.8 mN m−1. This work demonstrates that addressing the surface tension of large-volume ASNP inks is key to the reproducible fabrication of nanoparticle photovoltaic devices.

Barrier films are required for a number of applications such as food packaging or organic electronics to prevent product degradation results from exposure to water vapour and oxygen. In order to determine the effectiveness of polymers and deposited barrier films to inhibit water permeation, the water vapour transmission rate (WVTR) needs to be measured. The calcium test, MOCON instrument and tritiated water permeation can all be used to determine the WVTR, but the values produced by these techniques have not been extensively compared. The WVTR of two polymer substrates and two barrier films deposited onto polymer substrates have been measured using these three techniques. For a polyethylene terephthalate substrate and a MOCON reference film, similar WVTR were observed for all three techniques. For two commercially available barrier films, variable WVTRs were observed and attributed to film defects. WVTR measurements play an essential role in the use of polymers and barrier films to retard water permeation, therefore an understanding of the advantages and disadvantages of each technique is of great importance.

Nanoparticulate organic films are an attractive area of organic photovoltaic (OPV) research given their potential for controlling active layer morphology on the nanoscale. However, the power conversion efficiency of these devices remains limited in comparison to the analogous bulk heterojunction technology. Here, we report a systematic characterisation of charge carrier loss pathways in nanoparticulate OPVs prepared using poly(3hexylthiophene) as a donor and phenyl-C-61-butyric acid methyl ester as an acceptor material. Optical modelling of the nanoparticle active layer morphology indicates minimal losses from scattering and negligible plasmon effects from the discrete 40 nm particles. A comparison of the modelled internal absorption for the nanoparticle films confirms negligible differences in comparison to a standard bulk heterojunction active layer structure. By contrast, the internal quantum efficiency (IQE), determined with the aid of optically modelled internal active layer and parasitic non-active layer absorption, exhibited values of 24% for the nanoparticle device whilst the bulk heterojunction showed a value of 76%. Subsequent modelling of the EQE and IQE (supported by photoluminescence quenching measurements) indicated an exciton dissociation yield of 24% for nanoparticulate devices in comparison to 81% for the corresponding bulk heterojunction, in excellent agreement with the device internal quantum efficiencies. Transient measurements of charge transport and bimolecular recombination lifetime revealed a charge carrier drift length longer than the film thickness at short circuit conditions for both device structures. Impedance spectroscopy measurements confirmed very low photoinduced chemical capacitances at short circuit and returned charge collection efficiencies in excess of 80% for both devices, suggesting only minor charge collection losses in either device at short circuit. Collectively, these results demonstrate that the dominant photocurrent loss mechanism in nanoparticulate OPVs is a poor charge generation yield rather than reduced light absorption, increased bimolecular recombination or charge extraction barriers.

We present the optimization and upscaling of water-based nanoparticle inks based on a novel donor-acceptor pair consisting of poly(3-hexylthiophene) (P3HT) and a newly developed indene-C60 multiadducts (ICxA) that is comprised of indene-C60 monoadduct (ICMA), indene-C60 bisadduct (ICBA), and indene-C60 trisadduct (ICTA). This material system has been used as a case study to explore the transition from OPV materials optimised for small-scale spin-coating to those optimised for large-scale printing. In particular, we have explored the effects of transitioning from a small-scale BHJ ink formulated from a high-cost acceptor to a large-scale NP ink formulated from a low-cost fullerene mixture. We show that it is possible to use a low-cost acceptor and to formulate the inks at scale with no loss in device performance.

The potential for organic electronic technologies to produce low-cost energy at large scales is often cited as the most attractive feature of these materials. Such aspirations depend on the ability of materials to be printed from solution at high speeds across large areas using roll-to-roll (R2R) processing. However, progressing the technology from the laboratory environment into the industrial manufacturing arena is highly challenging. Closing the gap between exciting laboratory scale insights and the industrial scale potential requires a new focus on upscaling existing technology. Some recent progress in this area is discussed, concentrating on the need to pursue research across several different scales simultaneously in order to most effectively optimize large-scale fabrication efforts. These discussions are placed in the context of a design philosophy that combines printing, coating, and vacuum-based procedures. The challenges associated with selecting, and subsequently synthesizing, the optimal materials for device construction at large scales are considered. Case histories that highlight the unique challenges encountered during printing, coating, and sputtering at the R2R scale are presented. Developing testing and characterization procedures that can interrogate organic photovoltaic device (OPV) structures in real time is also discussed, and the opportunity for new tools to probe device photophysics is highlighted. The collection of innovative approaches to R2R fabrication challenges discussed here highlights the exciting progress toward efficient OPV modules becoming a commercial reality.

A new type of lead-free, formamidinium (FA)-based halide perovskites, FASnI2Br, are investigated as light-harvesting materials for low-temperature processed p–i–n heterojunction solar cells with different configurations. The FASnI2Br perovskite, with a band-gap of 1.68 eV, exhibits optimal photovoltaic performance after low-temperature annealing at 75 °C. By using C60 as electron-transport layer, the device yields a hysteresis-less power conversion efficiency of 1.72%. The possible use of an inorganic MoO x film as a new type of independent hole-transport layer for the present tin-based perovskite solar cells is also demonstrated.

An efficient panchromatic planar perovskite solar cell is developed based on highly uniform, lead-reduced CH3NH3Sn0.5Pb0.5I3 perovskite films with full film-coverage on the substrates. We demonstrate here that full-coverage of the CH3NH3Sn0.5Pb0.5I3 films can be developed by a facile chlorobenzene-assisted spin-coating method. A power conversion efficiency of ~7% is achieved using low-temperature processes, which is among the best-reported performance for panchromatic planar perovskite solar cells with a light-absorption over 1,000nm.

We demonstrate a pathway for fully roll-to-roll (R2R) prepared organic solar cells in a normal geometry with a R2R sputtered aluminium top electrode. Initial attempts utilizing a stack geometry without an electron transport layer (ETL) failed to obtain working devices. By applying aluminium zinc oxide (AZO) as an ETL, and optimizing the AZO thickness, working printed OPV devices with an efficiency of 0.58% were obtained. Further optimization of the donor:acceptor ratio in the active layer increased the efficiency to 0.90%. This work demonstrates that normal geometry organic solar cells using a metal top contact can be produced using large scale production techniques.

We investigate the suitability of four different inorganic materials (chromium oxide (CrOX), titanium oxide (TiOX), aluminium doped zinc oxide (AZO) and zinc oxide (ZnO)) as electrode transport layers in fully roll-to-roll (R2R) fabricated P3HT:ICxA organic solar cells. CrOX and TiOX were found to be unsuitable, as the CrOX devices did not exhibit rectifying behaviour while the TiOX devices did not withstand the annealing conditions. Of the last two ETLs, ZnO showed by far the most promise with devices demonstrating an average efficiency of 2.2%, which is the highest reported value for R2R devices in normal geometry, and a significantly extended lifetime compared with AZO devices under ISOS-L-2 conditions.