Periodic Reporting for period 1 - Light UP (Visible Light Ultrafast Photodetector for Optical Wireless Communication Technology)
Reporting period: 2020-03-01 to 2022-02-28
The exponential growing demand for wireless data traffic requires new technologies to overcome the limited bandwidth of the radio frequency spectrum. Nowadays, people can exploit light to surf the web in a fast and inexpensive way, without any need for radio waves, thanks to optical wireless communication technology (OWC). OWC take advantage from the large bandwidth of UV-Vis-IR regions of electromagnetic spectrum overcoming the limits of radio frequencies and allowing wireless network access in situations where radio communication is undesired for security or health hazard risk, e.g. on aircrafts, in hospitals or industrial installations. OWC is now ready for the next engineering challenge that is the development of ultrathin, transparent, lightweight, and stretchable OWC components for wearable applications, for which significant step forward are needed. Substantial advances must be made in materials design and device fabrication in order to meet the technological requirements dictated from unconventional device supports such as clothes, mechanically flexible design materials and even human skin. Therefore, one of the main challenges in this field is to develop a new generation of photodetectors with high performance in terms of detection speed, efficiency, stretchability and mechanical flexibility. Traditional bulk semiconductors are not suitable for this application since they are rigid and cannot easily conform to flexible and stretchable substrates, limiting the full exploitation of OWC technology. At the same time, the poor optical and electrical properties of mechanically flexible organic materials cannot support the development of competitive OWC.
Light UP has the ambition to transform the scenario of wearable OWC technologies by developing a conceptually new class of highly sensitive and wearable photodetectors with an expected time response as fast as a few tens of picoseconds, corresponding to an operational bandwidth in the GHz range, greatly surpassing any rivalling present wearable technology. This breakthrough exploit high-quality hybrid two-dimensional material with quantum well structure implemented in devices with optimized geometry. This emerging class of materials hold great potential due to their gamut of electrical, optical and mechanical properties that can be customized at will trough a straightforward and effective solution-phase synthetic approach toward the demonstration of wearable ultrafast photodetectors for OWC.
Such an ambitious objective is not only justified by fundamental scientific interest but also by the impact that could offer in several fields including assisted living, enhanced learning, healthcare, defence and security thus providing great benefit for people aged 60 and over with chronic disease, pregnant women, kids, and more in general for the vast majority of population groups. For example, wearable ultrafast photodetectors implemented with Light UP methodologies have all the potentialities to find application in OWC for health care enabling the development of nearly imperceptible and comfortable health monitoring through wearable devices optically connected excluding the risk of interference with sensitive equipment, as in case of radio waves.
Light UP has the ambition to transform the scenario of wearable OWC technologies by developing a conceptually new class of highly sensitive and wearable photodetectors with an expected time response as fast as a few tens of picoseconds, corresponding to an operational bandwidth in the GHz range, greatly surpassing any rivalling present wearable technology. This breakthrough exploit high-quality hybrid two-dimensional material with quantum well structure implemented in devices with optimized geometry. This emerging class of materials hold great potential due to their gamut of electrical, optical and mechanical properties that can be customized at will trough a straightforward and effective solution-phase synthetic approach toward the demonstration of wearable ultrafast photodetectors for OWC.
Such an ambitious objective is not only justified by fundamental scientific interest but also by the impact that could offer in several fields including assisted living, enhanced learning, healthcare, defence and security thus providing great benefit for people aged 60 and over with chronic disease, pregnant women, kids, and more in general for the vast majority of population groups. For example, wearable ultrafast photodetectors implemented with Light UP methodologies have all the potentialities to find application in OWC for health care enabling the development of nearly imperceptible and comfortable health monitoring through wearable devices optically connected excluding the risk of interference with sensitive equipment, as in case of radio waves.
Project activities enabled significant scientific and technological progress demonstrating highly sensitive and ultrafast flexible photodetectors for wearable OWC. We exploited emerging 2D hybrid perovskites characterized by an appealing natural quantum well structure consisting of alternating organic and inorganic layers with the organic part acting as a potential barrier for charges that remain confined in the inorganic layer. The precisely control of the solution-phase growth enabled the synthesis of high quality single crystalline 2D hybrid perovskites with precise quantum well width and optical and electrical properties suitable for the efficient and fast conversion of visible light in electrical signal. Single-crystal 2D hybrid perovskite flakes have been successfully integrated into high performance planar photodetectors, which are highly responsive at visible wavelength exhibiting photoresponsivity >1000 A/W and external quantum efficiency greatly exceeding 100%. Such devices exhibit also very low dark current, electrical noise and high photodetectivity enabling the detection of very weak light signals. In addition, devices are efficient in detecting very high intensity light signals resulting in a linear dynamic range > 200 dB. These outstanding performance are nicely complemented with ultrafast time response and a bandwidth > 2GHz which is highly sought for optical communication applications. Most importantly 2D hybrid perovskite planar photodetectors have been fabricated on relevant wearable flexible media, such as PET, with no need of substrate planarization and without losses of any performance even after a large number of bending cycles (>1000) in atmosphere condition.
The optimization of the quantum well structure in 2D hybrid perovskites and device geometry enabled the realization of wearable photodetectors exhibiting an unprecedented combination of excellent performances. In comparison to the state-of-the-art perovskite devices, flexible 2D hybrid perovskite photodetectors developed in Light UP exhibit several order of magnitudes higher responsivity, detectivity and linear dynamic range reaching and surpassing rigid commercial silicon photodiode performances.
The prototype of flexible Light UP photodetector pave the way towards the development of next generation optical connection systems based on conformal devices, which can ensure a safe and ultrafast connectivity, based on light signal. The societal and economic impact that these devices can enable will be transformative for the fields of healthcare, sport, education, and defence improving societal wealth through a safer environment, agile communication and the timely detection of health conditions.
The prototype of flexible Light UP photodetector pave the way towards the development of next generation optical connection systems based on conformal devices, which can ensure a safe and ultrafast connectivity, based on light signal. The societal and economic impact that these devices can enable will be transformative for the fields of healthcare, sport, education, and defence improving societal wealth through a safer environment, agile communication and the timely detection of health conditions.