Sensors based on organic electronic devices are emerging in a wide range of application areas. Here we present a sensor
platform using organic light emitting diodes (OLED) and organic photodiodes (OPD) as active components. By means of
lamination and interconnection technology the functional foils with OLED and OPD arrays form an in-plane optical
sensor platform (IPOS). This platform can be extended with a wireless data and signal processing unit yielding a sensor
node. The focus of our research is to engage the node in a healthcare application, in which a bandage is able to monitor
the vital signs of a person, a so-called Smart Bandage. One of the principles that is described here is based on measuring
the absorption modulation of blood volume induced by the pulse (photoplethysmography). The information from such a
bandage could be used to monitor wound healing by measuring the perfusion in the skin. The OLED and OPD devices
are manufactured on separate foils and glass substrates by means of printing and coating technologies. Furthermore, the
modular approach allows for the application of the optical sensing unit in a variety of other fields including chemical
sensing. This, ultimately enables the measurement of a large variety of physiological parameters using the same bandage
and the same basic sensor architecture. Here we discuss the build-up of our device in general terms. Specific
characteristics of the used OLEDs and OPDs are shown and finally we demonstrate the functionality by simultaneously
recorded photoplethysmograms of our device and a clinical pulseoximeter.
Marc Koetse, Peter Rensing, Ruben Sharpe, Gert van Heck, Bart Allard, Nicole Meulendijks, Peter Kruijt, Marcel Tijdink, René De Zwart, René Houben, Erik Enting, Sjaak van Veen, Herman Schoo
Monitoring of personal wellbeing and optimizing human performance are areas where sensors have only begun
to be used. One of the reasons for this is the specific demands that these application areas put on the underlying
technology and system properties. In many cases these sensors will be integrated in clothing, be worn on the skin,
or may even be placed inside the body. This implies that flexibility and wearability of the systems is essential for
their success. Devices based on polymer semiconductors allow for these demands since they can be fabricated
with thin film technology. The use of thin film device technology allows for the fabrication of very thin sensors
(e.g. integrated in food product packaging), flexible or bendable sensors in wearables, large area/distributed
sensors, and intrinsically low-cost applications in disposable products. With thin film device technology a high
level of integration can be achieved with parts that analyze signals, process and store data, and interact over a
network. Integration of all these functions will inherently lead to better cost/performance ratios, especially if
printing and other standard polymer technology such as high precision moulding is applied for the fabrication.
In this paper we present an optical transmission sensor array based on polymer semiconductor devices made by
thin film technology. The organic devices, light emitting diodes, photodiodes and selective medium chip, are
integrated with classic electronic components. Together they form a versatile sensor platform that allows for the
quantitative measurement of 100 channels and communicates wireless with a computer. The emphasis is given
to the sensor principle, the design, fabrication technology and integration of the thin film devices.
Ruben B. A. Sharpe, Peter Rensing, Gert van Heck, Bart A. M. Allard, Marc Koetse, Nicole N. M. M. Meulendijks, Peter G. M. Kruijt, Marcel W. W. J. Tijdink, René de Zwart, Sjaak J. J. F. van Veen, Herman F. M. Schoo
The introduction in the market of ubiquitous sensing applications relies heavily on the availability of affordable
sensors. Key in the cost of a sensor is its modus of manufacture. In this paper a sensing scheme is presented,
in which the signal transduction is based on an induced change in the optical path between an organic light
emitting diode (OLED) and an organic photovoltaic (OPV) array. Using this platform, several aspects of cost
efficient manufacturing technology are investigated. These aspects include the intrinsic printability of the active
(OLED, responsive coating and OPV) components, which allows control of the local sensor functionality and
sensitivity. It offers a large amount of freedom in sensor layout, while using relatively few process steps. Also
investigated is the ability to realize the active devices on foil, which enables high throughput processing (e.g. in
a reel-to-reel scheme). Moreover, the presented generic sensing scheme is of a modular design. It allows easy
switching of the sensor functionality mostly by simply changing the transduction module. Since this does not
affect the production parameters of the other components, these may be standardized, thus invoking favorable
economies of scale.
KEYWORDS: Polymers, External quantum efficiency, Absorption, Solar cells, Quantum efficiency, Luminescence, Electrodes, Transmission electron microscopy, Photovoltaics, Solar energy
We present a highly fluorescent polymer poly[2,7-(9,9'-dioctylfluorene)-alt-1,4-bis(1-cyanovinyl-2-thienyl)-2-methoxy-5-(3,7-dimethyloctyloxy)phenylene] (PF1CVTP), that was found to perform exceptionally well as electron acceptor in polymer photovoltaic devices when mixed with poly(2-methoxy-5-(3,7-dimethyloctyloxy)-1,4-phenylenevinylene) (MDMO-PPV) as electron donor. The optical and electrochemical properties of the blend were investigated. Both the quenching and the position of the oxidation and reduction waves indicate that charge transfer could take place if the blend is illuminated. Solar cell devices were made of blends containing different ratios of donor and acceptor. Maximum external quantum efficiency of more than 50 % was obtained and a power conversion efficiency of up to 1.5 % was measured under AM1.5 G (100 mW/cm2) conditions.
In hybrid polymer photovoltaics, conjugated polymers are combined with wide bandgap metal oxide semiconductors like TiO2 or ZnO. Reported maximum power conversion efficiencies (PCE) at AM1.5G conditions for a hybrid polymer bulkheterojunction device are up to 1.6 %. In this paper we report on the current-voltage characteristics of bi-layer devices consisting of TiO2 and a conjugated polymer. Several polymers with different optical bandgap were studied. The maximum External Quantum Efficiency (EQE) of the devices is comparable, but the PCE differs considerably (0.2-0.5%). The differences can for a large part be explained by the differences in optical bandgap of the polymers. It is shown that a low band gap is beneficial for the short circuit current, but does not automatically result in a high PCE as relative shifts of the highest occupied molecular orbital (HOMO) energy levels of the polymers reduce the open circuit voltage (Voc). The calculations show that a PCE up to ~ 19 % can be achieved using the maximum possible Voc and a fill factor of 80%. Judicious engineering of material combinations is required to achieve such a power output, and it expresses the need for a continuing search on potentially low cost, efficient metal oxide/polymer BHJ structures.
The photophysical properties of a solution processed blend of two semiconducting polymers with electron donating and electron accepting properties, respectively, as used in polymer photovoltaic devices have been investigated. In the binary mixture of poly[2-methoxy-5-(3,7-dimethyloctyloxy)-1,4-phenylenevinylene] (MDMO-PPV) and poly[oxa-1,4-phenylene-(1-cyano-1,2-vinylene)-(2-methoxy-5-(3,7-dimethyloctyloxy)-1,4-phenylene)-1,2-(2-cyanovinylene)-1,4-phenylene] (PCNEPV) photoexcitation of either one of the polymers results in formation of a luminescent exciplex at the interface of the two materials. The high energy of this correlated charge-separated state is consistent with the high open-circuit voltage of the corresponding solar cells (1.36 eV). Application of an electric field results in dissociation of the marginally stable exciplex into charge carriers, which provides the basis for the photovoltaic effect of this combination of materials.
Polymer bulk hetero junction solar cells were made from poly(2-methoxy-5-(3,7-dimethyloctyloxy)-1,4-phenylene-vinylene) (MDMO-PPV) as donor and poly(cyanoetherphenylenevinylene) (PCNEPV) derivatives as acceptor material. In this paper we start out with discussing the synthesis of the materials. Subsequently, the main issues concerning the devices are treated. Annealing the devices yielded devices with encouraging efficiencies of 0.5% (1 sun, 100mW/cm2), as calculated from the maximum power points (MPP). AFM studies revealed that this anneal step improves especially the interface of the active layer with the under laying PEDOT:PSS, although mobility and morphology changes can not be ruled out. Lowering the molecular weight (Mw) of the MDMO-PPV gave a slight improvement of the device performance. Decreasing the Mw of the acceptor material, MDMO-PCNEPV (PCNEPV derivative with the same side chains as MDMO-PPV) and optimizing the layer thickness led to a device with an efficiency of 0.65%. Finally we looked into the influence of the nature of the side chains on the acceptor polymer. The results suggest that the closer the resemblance between donor and acceptor is the better the device performance.
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