Neuroinspired device architectures offer the potential of higher order functionalities in information processing beyond their traditional microelectronic counterparts. In the actual neural environment, neural processing takes place in a complex and interwoven network of neurons and synapses. In addition, this network is immersed in a common electrochemical environment and global parameters such as ionic concentrations and concentrations of various hormones regulate the overall behaviour of the network. Here, various concepts of organic neuromorphic devices are presented based on electrochemical concepts. By utilizing these concepts, various neuromorphic functions are demonstrated, including temporal and spatial paradigms of information processing.

We have previously studied the photo-switching performances of azobenzene dithiophene derivative (AzBT) (1) inserted in nanoparticle self-assembled networks (NPSAN) nanodevices.(2) Here, we integrate AzBT-NPSAN in sub-100 nm 6-terminals devices (2 inputs, 4 outputs) and we demonstrate optically-driven reconfigurable Boolean operations associated to the light controlled switching of the molecules. Depending on the conductance pathways inside the AzBT-NPSAN, we identify 3 main output functions with a reconfiguration yield of 65%.(3) Contrary to previous results,(4) the devices work at room temperature and fully exploit the functionality of the molecules (and not Coulomb blockade in NPs). In addition, redox molecule NPSANs exhibit giant NDR (negative differential resistance) and memory effect.(5) We also investigate how complex non-linearity in the AzBT-NPSAN leads to High Harmonics Generation (HHG), one of the prerequisites of reservoir computing (RC) approaches.(6,7) We show that HHG can be modified by UV illumination which paves the way for the processing of multi-input signals through a device that acts as a reservoir computer. Finally, temperature dependent measurements (4K) demonstrate light-driven increase of co-tunneling into these molecular networks. Acknowledgement This work has been financially supported by EU-FET projects SYMONE and RECORD-IT. References 1) K. Smaali et al., ACS Nano 2010, 4, 2411–2421; S.Karpe et al. Chem. Comm. 2010, 46, 3657–3659. 2) Y. Viero et al., J. Phys. Chem. C, 2015, 119 (36), 21173–21183. 3) Y. Viero et al., in preparation 4) S.K. Bose et al., Nature Nanotech. 2015, 10, 1048–1053. 5) T. Zhang et al., ACS Nano, submitted 6) W. Maass et al., Neural Computation, 2002, 14, 2531-2560. 7) Y. Viero et al.,in preparation.

In this contribution, we report on a series of carefully conducted experiments to rationalize the role of metal nanoparticles embedded into conjugated organic materials, and address whether the NPs’ charging/discharging plays a role in the resistive switching of R-NVMs. The electronic and electric behaviour of the hybrid NP/organic materials was investigated via ultraviolet photoemission spectroscopy, as well as impendence spectroscopy. Our results provide evidence that the most commonly proposed charging/discharging mechanisms can be excluded as the working mechanism, and there is solid evidence that resistive switching is due to the formation/rupture of filaments.

Recent studies have found that responses to electrical stimulations in organic semiconductors and/or electrolytes heterogeneous junctions possess features in common with neural synaptic plasticity. Thus, we explore spatial summation of short-term plasticity by using a pair of such junctions. A simple integration of parallel connection displayed frequency selectivity in the weight modification of charging peaks but not for discharging peaks. Significantly, the weight modification could be linearly summed from those of the two source devices though the absolute peak currents could not. Our system is feasible for synaptic computation including spatial summation and direction selectivity in artificial neural network.

This paper will firstly introduce the electrical requirements on the memories to be operated in power constrained mobile readout systems for secure packaging applications. Then, two types of printed read-only memories (ROMs), including polymer resistive type ROM and fuse-type electrically programmable ROM, are presented. The fabricated polymer resistive ROM tags present extremely stable performance under both aging and electrical stress tests in air ambient. Fuse-type ROMs were fabricated with a new cell structure to achieve multi-bit memories with greatly saved contact pad numbers. The functions of the printed ROMs are finally demonstrated with mobile readout hardware systems.

Organic electronics has been thoroughly investigated as technology for the fabrication of flexible devices enabling a wide range of applications including disposable electronics, smart cards, flexible displays, wearable electronics and sensors. In this work we present the different solutions we have developed for the routinely fabrication of inkjet printed organic transistors, operating a very low voltages and we report about their employment in the realization of different kinds of sensor devices. Moreover, we will also report about the fabrication of high performing printed memory devices using different approaches, as field effect transistors and resistive switching elements.

Organic ferroelectric memory diodes are promising candidates for non-volatile memory applications. A microstructure is needed that consists of bicontinuous columns of a semiconducting polymer embedded in the matrix of ferroelectric copolymer of vinylidenefluoride with trifluoroethylene (P(VDF-TrFE)). Memory diode is realized by deliberately choosing an injection limited contact. Depending on the ferroelectric polarization, the current density is high and the diode is in the on-state or the current density is low and the diode is in the off-state. In this contribution we discuss the device physics of the diodes by taking into account polarization dynamics, and give the limits for upscaling.

We report multilevel resistive switching using an organolead halide perovskite (OHP). Solution-processed 400 nm thick CH3NH3PbI3 films with Ag top and Pt bottom electrodes exhibited electroforming-free resistive switching with a low SET voltage of ~0.13 V and high ON/OFF ratios of ≈10^6 under ±0.15 V pulses. Based on these extraordinary properties, four-level storage capability of the CH3NH3PbI3-based devices was demonstrated. We attributed the high performance resistive switching behavior of the CH3NH3PbI3-based devices to the energetically benign migration of anions defects, but further studies are needed to identify the mechanism responsible for the ultralow electric field resistive switching. Enhancements in switching speed, endurance, and retention are also necessary and may be achieved by controlling the doping concentration, crystallinity, and large area compositional uniformity of the OHP film. The inherent structural flexibility and the number of possible combinations for ABX3-type OHPs will support intensive studies for other electronic device applications beyond resistive switching memories. Finally, we believe that the solution-processed CH3NH3PbI3-based cells are promising for microelectronics built on flexible substrates.

Organic nonvolatile memories can be key components toward future low-cost, light-weight, flexible and portable electronic products. The memories based on organic field-effect transistors (OFETs) possess advantages of nondestructive reading, capability to integrate data processing and storage, and compatibility with various substrates. OFET nonvolatile memories face the challenge of simultaneously achieving large memory window, high air stability, long retention time and good rewritable endurance. We firstly elucidate the charge trapping/detrapping mechanism in the memories by a variety of approaches [1-9], including (1) in-situ surface potential mapping, (2) design and tailoring of nano-floating-gate, (3) characterization on memory ambient stability, (4) light response of memory behaviors and (5) probing of current transition point. The charge trapping/detrapping mechanism turns out to be a complex process dependent on both external electrical/optical fields and internal material properties. Secondly, the OFET nonvolatile memories are demonstrated to be promising in the applications of multibit data storage and solar-blind photodetection. References: [1] Wang, S.; Gao, X.; Zhong, Y. N.; Zhang, Z. D.; Xu, J. L.; Wang, S. D. Appl. Phys. Lett. 2016, 109, 023301. [2] Liu, J.; Wang, C. H.; Liu, C. H.; Li, Q. L.; Gao, X.; Wang, S. D. Adv. Electron. Mater. 2016, 2, 1500349. [3] Zhang, J. Y.; Liu, L. M.; Gao, X.; Liu, C. H.; Liu, J.; Dong, B.; Wang, S. D. Org. Electron. 2015. 25, 324-328. [4] Cui, Z. Q.; Wang, S.; Chen, J. M.; Gao, X.; Dong, B.; Chi, L. F.; Wang, S. D. Appl. Phys. Lett. 2015. 106, 123303. [5] Liu, J.; Liu, C. H.; She, X. J.; Sun, Q. J.; Gao, X.; Wang, S. D. Appl. Phys. Lett. 2014. 105, 163302. [6] Gao, X.; Liu, C. H.; She, X. J.; Li, Q. L.; Liu, J.; Wang, S. D. Org. Electron. 2014. 15, 2486-2491. [7] She, X. J.; Liu, J.; Zhang, J. Y.; Gao, X.; Wang, S. D. Appl. Phys. Lett. 2013. 103, 143302. [8] She, X. J.; Liu, C. H.; Zhang, J. Y.; Gao, X.; Wang, S. D. Appl. Phys. Lett. 2013. 102, 053303. [9] Gao, X.; She, X. J.; Liu, C. H.; Sun, Q. J.; Liu, J.; Wang, S. D. Appl. Phys. Lett. 2013. 102, 023303.

Thermoelectric generators (TEGs) are an attractive means of energy harvesting for wearables and sensor nodes for the Internet-of-Things (IoT). As a unique feature, organic semiconductors and inorganic nanomaterials offer printability. This opens a pathway for thermoelectric generators with unprecedented low costs thus enabling mass consumer applications. We have developed inks and a device layout which allow for a roll-to-roll printing process on ultrathin plastic foils. The TEGs are then fabricated by an automated folding process which allows to adapt the geometry of the devices for the application. Several wireless sensor nodes using thermoelectric energy harvesting are demonstrated.

Printed electronics (PE) is an emerging technology with potential applications in flexible displays, smart labels, wearable electronics, soft robotics, and prosthetics. While conventional electronics are fabricated on rigid, inorganic substrates, solution processed materials are compatible with plastic film substrates that are flexible, soft, and stretchable, thus enabling conformal integration with curvilinear objects. In addition, manufacturing by printing is scalable to large areas and is amenable to low-cost sheet-fed and roll-to-roll processes. PE includes display and sensory components to interface with users and environments. On the system level, PE also requires electronic circuits for power, memory, signal conditioning, and communications. Those electronic components can be integrated onto a flexible substrate by either assembly or printing. PARC has been developing systems and processes for realizing both of these approaches. This talk will present PE fabrication methods with an emphasis on techniques recently developed for the assembly of off-the-shelf chips. A few examples of PE systems fabricated with this approach will also be described.

Wearable electronics has emerged into the consumer markets over the past few years. Wrist devices and textile integration are common technologies for unobtrusive measuring in sport and wellbeing sectors. Disposable bandages represents a paradigm shift in wearable electronics. Soft-electronics can conform to temporary transfer tattoo and deform with the skin without detachment or fracture. In this presentation, we focus on printed soft-electronics for remote body monitoring. We will present fabrication and characterization of electrode bandage and temperature sensor.

We demonstrate bladecoated polymer light-emitting diodes (PLEDs) for optoelectronic sensors. We use surface energy patterning (SEP) with bladecoating to obtain reproducible and homogeneous films. Green, red and near-infrared (NIR) PLEDs are demonstrated and characterized. SEP technique is further utilized to print different colors on a same substrate in a single bladecoating process. We use solid-state components to help design the optoelectronic sensors. Based on the observation, PLEDs are used in conjunction with a silicon photodiode to perform oxygenation measurement.

For at least the past 10 years, printed electronics has promised to revolutionize our daily life by making cost-effective electronic circuits and sensors available through mass production techniques, for their ubiquitous applications in wearable components, rollable and conformable devices, and point-of-care applications. While passive components, such as conductors, resistors and capacitors, had been already fabricated by printing techniques at industrial scale, despite the great potentiality, printing processes have been struggling to meet the requirements for mass-produced electronics and optoelectronics applications. In the case of logic integrated circuits (ICs), the main limitations have been represented by the need of suitable functional inks, mainly high-mobility printable semiconductors and low sintering temperature conducting inks, and evoluted printing tools capable of higher resolution, registration and uniformity than needed in the conventional graphic arts printing sector. In this presentation, I will give a talk on the recent progressive of my group on development of printed organic integrated circuits. I will mainly talk about on development of high performance inkjet printed unipolar and ambipolar polymer field-effect transistors (FETs), and applications to elementary organic complementary logic circuits by applying novel polymer dielectrics, new organic semiconducting and design new printing processes.

Electronic sensor skins is an active area of research for many groups over the world due to its potential to enable dramatic changes in how we interact with the digital environment. For example, ‘robots’ can don on sensor active skins to shake human hands with comfortable pressure, measure our health biometrics and possibly aid in wound healing. In my talk, I will discuss the development of electronic sensor skins with some historical context, followed by showcasing of several force sensitive electronic skin technologies with high sensitivity, stretchability and bio-mimetic self-healing abilities. More recently, we demonstrated a power-efficient frequency encoded artificial mechano-receptor system inspired by biological mechano-receptors4. We further used a channelrhodopsin with fast kinetics and large photocurrents as an optical interface to neuronal systems for next generation opto-tactile prosthetic interfaces.

Printed electronics is revolutionising the electronics industry by enabling additive processing that significantly reduces expense, waste and energy consumption. We therefore present the process development of solution-processed electrodes based on inkjet-printed Cu grids, by embedding the inkjet-printed metal grids to yield ITO-free optoelectronic devices. Secondly, we present roll-to-roll inkjet-printed RFID antennas based on Cu inks. Finally, we demonstrate a truly low-temperature sintering route for a Cu nanoparticle ink by using a reducing atmosphere of formic acid, yielding stable highly conducting layers. The results highlight overall parameters for solution processing and implementation of novel metal nanoparticle materials in printed electronics.

Thin film transistors (TFTs) with organic and single-walled carbon nanotube (SWCNT) semiconducting materials are reported for facile inkjet-printing process compatibility, transparent electronics applications, and hybrid complementary metal oxide semiconductor (CMOS) circuits. Technical issues of source/drain (S/D) contact improvement via organo-compatible, single-step interface engineering for organic TFTs with silver and organic S/D electrodes, fabrication and performance stability of transparent TFTs under visible light illumination, significant reduction of fabrication process time of SWCNT TFTs, and low-voltage (< 5V) operation of hybrid CMOS inverters with solution-process high-k dielectric and n-type oxide semiconducting materials for both organic and SWCNT TFTs, will be further discussed. This work was supported by the Center for Advanced Soft-Electronics funded by the Ministry of Science, ICT and Future Planning as Global Frontier Project (CASE-2015M3A6A5065309).

Iron oxide nanoparticles (IONPs) are among the most promising candidates for nano-scale magnetic memory applications due to their excellent magnetic properties. The general drawback of IONPs is the lack of ferromagnetism in IONPs at room temperature. To overcome this issue, doping of IONPs with cobalt is suggested. In this contribution we present a systematic study of Co doped IONPs using heat-up synthesis methods. The synthesis was optimized to obtain sub-20 nm monodisperse ferromagnetic nanoparticles with optimum magnetization and coercivity values. Ferromagnetic nanoparticles can be processed from solution to form a ferromagnetic thin-film and are suitable for low-cost non-volatile memory application.

Organic nonvolatile memory based on OFET is an essential element in organic electronics, which integrates nondestructive data processing and reliable data storage [1,2]. It is reported the memory window is sensitive to light illumination. However, the fundamental of the light-assisted program, especially the photon energy dependence of memory performance, needs to be clarified with a clear physical picture. In our work, the charge trapping process in the organic nano-floating-gate memory was comparatively studied by light response measurements, where light sources with different wavelengths of 408 nm, 532 nm, and 652 nm were employed. The positive threshold voltage shift was observed for all lights and increased up raising the light intensity, while the negative threshold voltage shift was only observed under 408 nm light illumination. It is proposed that the light with photon energy higher than the HOMO–LUMO gap of pentacene can induce the minority multiplication effect, which leads to significant positive threshold voltage shift but no obvious impact on negative threshold voltage shift. Whereas the light with photon energy in excess of the injection barriers at the pentacene/PS interface can additionally cause the excitation-induced injection effect, corresponding to hole injection into floating gate from the HOMO of pentacene, which realizes further negative threshold voltage shift [3]. The photon-energy-dependent light effects could be utilized to reduce the operation voltage of organic nano-floating-gate nonvolatile memories, and motivate the development of organic energy-resolved photosensors. References: [1] Y. L. Guo, G. Yu, Y. Q. Liu, Advanced Materials, 2010, 22, 4427-4447. [2] X. J. She, C. H. Liu, Q. J. Sun, X. Gao, S. D. Wang, Organic Electronics, 2012, 13, 1908-1915. [3] X. Gao, C. H. Liu, X. J. She, Q. L. Li, J. Liu, and S. D. Wang, Organic Electronics, 2014, 15, 2486-2491.