Fully Spray Coated Organic Photodiodes

Siemens AG, Corporate Technology, CT MM1, Gunther-Scharowsky-Strasse 1, 91058 Erlangen, Germany.
Nano Letters (Impact Factor: 13.59). 03/2009; 9(3):980-3. DOI: 10.1021/nl803386y
Source: PubMed

ABSTRACT Solution-processed organic diodes based on bulk heterojunctions are attractive for large area photodetection. We report a general approach for fully spray-coated organic photodiodes with outstanding characteristics in comparison to bladed or spin-coated devices. Despite the high surface roughness and the less defined morphology of the spray-deposited organic layers, we observe organic photodetectors with responsivities of 0.36 A/W and noise equivalent powers of 0.2 pW/H(1/2) in the visible spectrum at high reverse biases of -5 V. Furthermore, we demonstrate device lifetimes beyond 1 year as well as superior yield and reproducibilties for the dark current and photocurrent densities.

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    • "c o m / l o c a t e / o r g e l in the emerging organic electronics field because it leads to homogeneous films with delimited large area on different substrates by using virtually any kind of fluid. Indeed, in the last 5 years a crescent number of publications have introduced the conventional spray as an efficient way to get buffer, active or emissive thin layers or even transparent conductive electrodes in organic photovoltaics (OPV), organic transistors (OFETs) and photodiode structures [4] [5] [6] [7]. "
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    ABSTRACT: In this contribution we explore the spray deposition technique to achieve smooth films based on the conductive polymer PEDOT:PSS. Two different spray systems were used and compared namely: (a) handheld airbrush and (b) automated ultrasonic spray system. For each system a number of parameters were pre-adjusted during coating control experiments such as spray head distance, angle and cone for airbrush as well as flow rate, power and focus for ultrasonic nozzle. Water-based solutions of PEDOT:PSS having 20% of N-methylpyrrolidone (NMP) were sprayed on glass substrates at temperatures ranging from 75 to 150 °C. The resulting films were further chemically treated with ethylene glycol (EG) and evaluated with respect to their morphological, electrical and optical properties. Before EG-treatment the ultrasonic spraying resulted in smoother films with conductivity up to 2-3.9 times higher than their airbrushed counterparts. Deposition temperature proved to have minor effect on the morphological and electro-optical properties of PEDOT:PSS films. On the other hand, the film conductivity was enhanced, peaking at 610.1 S cm−1 for ultrasonic spraying, when further chemically modified by EG. IR microspectroscopy mapping analysis, Raman spectroscopy and XRD data indicated a phase-separation between PEDOT and PSS chains and increasing crystallinity in the ultrasonically sprayed films. The application of such PEDOT:PSS films as transparent electrode in flexible AC EL devices is demonstrated.
    Organic Electronics 05/2014; 15(5). DOI:10.1016/j.orgel.2014.02.022 · 3.83 Impact Factor
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    • "In this work we present for the first time an OVLC link that uses an Osram Orbeos CMW-031 OLED, (commercially available) as the transmitter and a custom OPD as the receiver. The OPD is produced under collaboration by Siemens AG Corporate Technology and is produced by spray coating at room temperature [10]. While specific material details are not available for the OLED, the OPD is based on the bulk heterojunction concept – an interpenetrated blend of electron donor (poly(3-hexylthiophene)) and electron acceptor ([6] [6]- phenyl-C61-butyric acid methyl ester) [11] (P3HT:PCBM), which is dissolved into a solvent and sprayed onto the substrate. "
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    ABSTRACT: This paper presents new experimental results on a 1 Mb/s organic visible light communications system. These results are the first demonstration of a fully organic free space optical communications system. Due to low charge transport characteristics, organic devices are typically highly band-limited in the hundreds of kHz region (up to 135 kHz in this work). Therefore an artificial neural network (ANN) equalizer is required to undo the effects of inter-symbol interference. Without the ANN the maximum link performance corresponds to a data rate of 350 kb/s, however with the ANN, a transmission speed of 1.15 Mb/s could be supported.
    IEEE Photonics Technology Letters 04/2014; 26(13):1-1. DOI:10.1109/LPT.2014.2321412 · 2.11 Impact Factor
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    • "Recent reports on organic imagers have demonstrated that non-structured OPDs on a-Si backplanes are attractive as alternative to pixelated a-Si PIN diodes due to the reduced lithography efforts12. In particular bulk heterojunction (BHJ)3 based OPDs have shown high external quantum efficiency (EQE) due to the high absorption coefficient of the absorber and low dark current densities4 at field strengths >10 V μm−1. Cut-off frequency values of ~1 MHz5 for standard OPDs and ~420 kHz6 for inverted OPDs were reported, though these values were derived on small active area devices tested with pulsed light illumination in the mW cm−2 range, which is several orders of magnitudes higher than the light intensity detected for X-ray imaging. "
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    ABSTRACT: Organic semiconductors are attractive for optical sensing applications due to the effortless processing on large active area of several cm(2), which is difficult to achieve with solid-state devices. However, compared to silicon photodiodes, sensitivity and dynamic behavior remain a major challenge with organic sensors. Here, we show that charge trapping phenomena deteriorate the bandwidth of organic photodiodes (OPDs) to a few Hz at low-light levels. We demonstrate that, despite the large OPD capacitances of ~10 nF cm(-2), a frequency response in the kHz regime can be achieved at light levels as low as 20 nW cm(-2) by appropriate interface engineering, which corresponds to a 1000-fold increase compared to state-of-the-art OPDs. Such device characteristics indicate that large active area OPDs are suitable for industrial sensing and even match medical requirements for single X-ray pulse detection in the millisecond range.
    Scientific Reports 02/2013; 3:1324. DOI:10.1038/srep01324 · 5.58 Impact Factor
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