The sensoristic approach based on OTFTs has recently been viewed as a focus of major interest because of their versatility, low cost and integration with microfluidics. In the simplest configuration of OTFT based sensors, the direct electrical detection of analytes is produced by the modulation of the device parameters due to the interaction of the device active layer with analytes [1] or light [2]. In particular, light sensing transistors (LS-OTFTs) represent an emerging application in view of the manufacturing of full organic Lab-on-Chip arrays for the selective detection of biomolecules or multifunctional, flexible, RGB sensors.LS-OTFTs basically exploit an organic semiconductive blend made of a donor-acceptor bulk heterojunction, acting as device channel in conventional TFT architectures. The as-prepared device shows an ambipolar behaviour whose OFF current is affected by the dissociation of excitons generated upon device light exposure.Key issues in terms of device operation and selectivity are the choice of the suitable donor polymer, to be combined with the acceptor organic material (generally fullerene derivatives) for the manufacturing of the active layer, and the engineering of the device architecture. In particular, device selectivity can be gained by changing the donor polymer and by coupling the device with suitable optical low-pass and high-pass filter, eventually hybrid or full organic, allowing thus the fabrication of flexible RGB filters. Sensor performances, such as the balance between the device p-type and n-type output currents, the strength of device parameter modulation, the lowest detectable power optical density and the sensor swiftness, are instead intimately correlated to the precursor concentrations, their mixing ratio, the post deposition treatment and the device architecture. In addition, LS-OTFT response can be enhanced introducing a short channel-low voltage operating OTFT acting as amplifier stage for the low LS-OTFT output OFF current, allowing the development of a light-biased current amplification stage.The first part of this talk will be focused on the analysis of LS-OTFT manufacturing and optimization process, showing how it is possible to obtain an OFF current modulation by two orders of magnitude in presence of selected monochromatic light (optical power density 100 µW/cm2), a low detectable optical power density of 2-3 µW/cm2 and a swiftness comparable the optical switching speed of commercial displays in the case of Bottom-Contac Top-Gate device with an organic dielectric barrier.Indeed, the second part of this talk will be focused on the testing of a TiO2-Dye high pass filter, coupled with a LS device for the selective detecting of visible light and a low-voltage operating OTFT to enhance the device current modulation. References [1] P.Stoliar et al. Biosens Bioelectron 2009, 24, 2935-2938.[2] T.D. Anthopoulos Appl Phys Lett 2007,91,113513.
An Overview on Light Sensing Organic Thin Film Transistor: From Basic Operating Properties towards High Performance, Selective Sensors.
2011
Abstract
The sensoristic approach based on OTFTs has recently been viewed as a focus of major interest because of their versatility, low cost and integration with microfluidics. In the simplest configuration of OTFT based sensors, the direct electrical detection of analytes is produced by the modulation of the device parameters due to the interaction of the device active layer with analytes [1] or light [2]. In particular, light sensing transistors (LS-OTFTs) represent an emerging application in view of the manufacturing of full organic Lab-on-Chip arrays for the selective detection of biomolecules or multifunctional, flexible, RGB sensors.LS-OTFTs basically exploit an organic semiconductive blend made of a donor-acceptor bulk heterojunction, acting as device channel in conventional TFT architectures. The as-prepared device shows an ambipolar behaviour whose OFF current is affected by the dissociation of excitons generated upon device light exposure.Key issues in terms of device operation and selectivity are the choice of the suitable donor polymer, to be combined with the acceptor organic material (generally fullerene derivatives) for the manufacturing of the active layer, and the engineering of the device architecture. In particular, device selectivity can be gained by changing the donor polymer and by coupling the device with suitable optical low-pass and high-pass filter, eventually hybrid or full organic, allowing thus the fabrication of flexible RGB filters. Sensor performances, such as the balance between the device p-type and n-type output currents, the strength of device parameter modulation, the lowest detectable power optical density and the sensor swiftness, are instead intimately correlated to the precursor concentrations, their mixing ratio, the post deposition treatment and the device architecture. In addition, LS-OTFT response can be enhanced introducing a short channel-low voltage operating OTFT acting as amplifier stage for the low LS-OTFT output OFF current, allowing the development of a light-biased current amplification stage.The first part of this talk will be focused on the analysis of LS-OTFT manufacturing and optimization process, showing how it is possible to obtain an OFF current modulation by two orders of magnitude in presence of selected monochromatic light (optical power density 100 µW/cm2), a low detectable optical power density of 2-3 µW/cm2 and a swiftness comparable the optical switching speed of commercial displays in the case of Bottom-Contac Top-Gate device with an organic dielectric barrier.Indeed, the second part of this talk will be focused on the testing of a TiO2-Dye high pass filter, coupled with a LS device for the selective detecting of visible light and a low-voltage operating OTFT to enhance the device current modulation. References [1] P.Stoliar et al. Biosens Bioelectron 2009, 24, 2935-2938.[2] T.D. Anthopoulos Appl Phys Lett 2007,91,113513.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
