Organic photodetectors (OPDs) hold great promise for use in flexible electronics as they can be designed on substrates featuring various shapes and using cost-effective solution-processed methods. Organic conjugated materials offering two or more distinct optoelectronic functions are especially appealing here as they provide multifunctionality while also retaining the ease of fabrication and low-cost advantage. One such material is TPA-azaBODIPY-TPA that has been shown to feature ideal charge transfer properties and excitation energy levels. In our recent work, we demonstrated the versatile nature of this material acting as either a charge transport interlayer in perovskite solar cells, or as a light-absorbing layer in OPDs. TPA-azaBODIPY-TPA-based solar cellsshowed a 60 % increase in power conversion efficiency when compared to a control device using a conventional interlayer PEDOT:PSS. Having also demonstrated the successful utilization of TPA-azaBODIPY-TPA in OPDs manufactured on glass substrates, we further explore its applications in the design and fabrication of flexible OPDs for near-infrared sensing. Fabricated devices on flexible substrates show a near-infrared spectral responsivity of 49 mA W-1 at 730 nm, a high linear dynamic range of 110 dB and fast temporal responses below 100 μs. With robust thermal stability as well as excellent solubility and processability, TPA-azaBODIPY-TPA is found to be perfect candidate for the next-generation of smart optoelectronic flexible devices.
Mapping neurons in the brain is important to understand the neuronal circuits involved in cognitive functions such as learning and memory formation. More importantly, understanding their dysfunction in neurological disorders and diseases could benefit patients that rely on better therapy interventions and techniques. To this aim, optogenetic tools, where light is used to control neuronal activity, and ultimately behavior, have revolutionized the field of neuroscience over the last 20 years. Current optogenetic approaches to investigate brain function involve the use of commercially available lasers and LEDs coupled to large implants, optical fibers or camera systems. Their use is usually associated with high cost, invasiveness and low spatial resolution. To address these limitations, organic electronic devices have been emerging as an alternative candidate for biocompatible, small-footprint, and high-resolution neural probes. In our own contribution to the field, we have demonstrated the successful detection of neuronal activity using organic photodetectors (OPDs) based on rubrene/C60, as well as direct optogenetic stimulation of neuronal activity using OLEDs based on Super Yellow. In this paper, we extend our previous work by demonstrating the stability and reliability of OPDs and OLEDs in optogenetics, and the effect of oxygen and encapsulation on the OPD/OLED performance. We also discuss the requirements for successful long-term neural recordings and determine the detection threshold for OPDs, (i.e. the required sensitivity to detect activity in a single neuron), as well as the minimum performance requirements in OLEDs to evoke neuronal activity.
Organic photodetectors are able to transform plastic into intelligent surfaces making our daily life easier, smarter and more productive. The key element for a sensor is to reduce the dark current density in order to boost the limit of detection. The energetic requirements in order to select materials for ultra-high performance organic photodetectors are presented with the following experimental results: a detectivity of 3.36 × 1013 Jones has been achieved with an extremely low dark current density of 0.32 nA cm-2 and a responsivity as high as 0.34 A W-1. Flexible devices are all made at lowtemperature and with solution-processed materials. Their stability under operation is also presented.
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