This PDF file contains the front matter associated with SPIE Proceedings Volume 10366, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and Conference Committee listing.

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 organic electrochemical transistors (OECTs). Regarding the implementation of neuromorphic devices, the key properties of the OECT that resemble the neural environment are also presented. These include the operation in liquid electrolyte environment, low power consumption and the ability of formation of massive interconnections through the electrolyte continuum. Showcase examples of neuromorphic functions with OECTs are demonstrated, including short-, long-term plasticity and spatiotemporal or distributed information processing.

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.

Printed read-only memory (ROM) would be a key component for many envisioned printed electronics applications such as item identification, anti-counterfeiting, brand protection and supply chain management. This paper will firstly introduce the electrical requirements on the memories to be operated in power constrained mobile readout systems for these targeted applications. Then, two types of printed ROMs, including polymer resistive type ROM and fuse-type electrically programmable write-once-read-many (WORM) ROM, will be presented. For the former, the instability issues associated with the conventional PEDOT: PSS and its interface with contact electrodes will be revealed. This work proves that, by removing the hydrophilic acidic groups in conventional PEDOT: PSS, these instability issues can be well addressed. The ROM tags fabricated based on the modified PEDOT: PSS of neutral pH and inkjet printed silver electrodes present extremely stable performance under both aging and electrical stress tests in air ambient. For the latter, fuse-type WORM ROMs are fabricated using a common material inkjet printer to form both the contact pads and the resistor tracks with the same silver ink and process settings. Based on the dependence of the fusing voltage on the length of the printed resistor track, a new cell structure is proposed to achieve multi-bit memories with greatly saved contact pad numbers for easier external electrical connections than the conventional design. The memory cells also present excellent long-term storage and operation stabilities. The function 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 displas, wearable electronics and sensors. However, in order to make such technology suitable for real applications, reliable, cost efficient approaches for large area fabrication, such as inkjet printing, have to be properly optimized. Moreover, in order to increase the final system portability, and as a consequence, its application range, such devices must be also operated at relatively low voltages. 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 for monitoring physical (pressure/temperature) and biochemical (eg. pH and/or DNA) stimuli and/or ionizing radiations. Moreover, the development of organic electronics systems requires also the integration of such smart sensing systems with reliable data storage devices. Among several possible solutions, we will demonstrate that inkjet printing can be employed for the fabrication of high performing memory devices using different approaches, based on printed transistors and resistive switching elements, and that, such devices, can be easily integrated with electrical sensors for the fabrication of printed, flexible smart tags.

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) transform heat to electricity without any movable parts. These devices are considered to be an important means of energy harvesting for wearables and sensor nodes for the Internet-of-Things (IoT). Organic semiconductors have recently demonstrated ZT-values approaching the same order of magnitude of those of the best established inorganic materials. Conjugated polymers as well as printable inorganic nanomaterials offer the unique advantage of being processable on printing machines. This opens a pathway for the fabrication of thermoelectric generators with unprecedented low costs thus enabling mass consumer applications. We have developed novel printable PEDOT formulations and a device layout which allow for a roll-to-roll printing process on ultrathin plastic foils. The TEGs are then subsequently fabricated by an automated folding process which allows to adapt the geometry of the devices such that the desired thermal resistance is optimum for the specific thermal boundary condition. Using this approach in combination with designed low power electronics forms the basis for several wireless sensor nodes.

Printed and flexible hybrid electronics is an emerging technology with potential applications in smart labels, wearable electronics, soft robotics, and prosthetics. Printed solution-based materials are compatible with plastic film substrates that are flexible, soft, and stretchable, thus enabling conformal integration with non-planar objects. In addition, manufacturing by printing is scalable to large areas and is amenable to low-cost sheet-fed and roll-to-roll processes. FHE includes display and sensory components to interface with users and environments. On the system level, devices also require 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 developed systems and processes for realizing both approaches. This talk presents fabrication methods with an emphasis on techniques recently developed for the assembly of off-the-shelf chips. A few examples of systems fabricated with this approach are also described.

Wearable electronics has emerged into the consumer markets over the past few years. Wrist worn and textile integrated devices are the most common apparatuses for unobtrusive monitoring in sports and wellness sectors. Disposable patches and bandages, however, represent the new era of wearable electronics. Soft and stretchable electronics is the enabling technology of this paradigm shift. It can conform to temporary transfer tattoo and deform with the skin without detachment or fracture. In this paper, we focus on screen-printed soft-electronics for remote body monitoring. We will present a fabrication process of a skin conformable electrode bandage designed for long-term outpatient electrocardiography (ECG) monitoring. The soft bandage is designed to be attached to the patient chest and miniaturized data collection device is connected to the bandage via Micro-USB connector. The fabricated bandage is tested in short exercise as well as continued long-term (72 hours) monitoring during normal daily activities. The attained quality of the measured ECG signals is fully satisfactory for rhythm-based cardiac analysis also during moderate-intensity exercise. After pre-processing, the signals could be used also for more profound morphological analysis of ECG wave shapes.

Here we demonstrate blade coated polymer light-emitting diodes (PLEDs) with different colors on a flexible substrate for optoelectronic sensor applications. Flexible electronics conform well to human body, which makes them favorable for wearable application. Blade coating is an attractive printing scheme to fabricate electronic devices, in that it is simple to configure and has high throughput. Here, surface energy patterning (SEP) is used to blade coat solution at desired areas. This technique reduces the amount of solution wasted through the sides of the blade, as compared to bladecoating without SEP, which leads to highly homogeneous active layer film and relatively consistent device performance. Using this technique, PLEDs with individual colors, red, green and near infrared (NIR) which are known colors that can be used to detect the condition of haemoglobin, are separately fabricated with blade coating. Luminous Efficacy and EQE of the PLEDs at 1Wsr-1m-2 were 42.7mW/W, 10% for Red, 31.2mW/W, 6.3% for Green, and 8.6mW/W, 3.1% for NIR. Also, SEP is further utilized to bladecoat two PLEDs with different colors on one substrate with no significant changes in the performance of the PLEDs. Before fabricating PLEDs for optoelectronic sensors we assessed design parameters such as minimum required flux and ideal distance between the light source and the detector using solid-state components. Based on the experiment, the PLEDs are fabricated to be used in conjunction with a photodiode to perform pulsating photoplethysmogram (PPG) measurements. Furthermore, with the multicolor PLEDs we successfully demonstrate 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. 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. In particular, we engineered and introduce new concept based for solution processed solid-state electrolyte gate insulators (SEGIs) by precise blending of P(VDF-TrFE) solution and P(VDF-HFP)-[EMIM][TFSI] gel solution resulting, after deposition of a thin film solid gate dielectric FETs, in ultrahigh field-effect mobility (μFET) and stable devices operating at low-voltage for several classes of unconventional semiconductors including -conjugated polymers, metal-oxides and other carbonaceous materials. By adding a minute amount (3% volume ratio for the optimal composition) of P(VDF-HFP)-[EMIM][TFSI] to the bulk fluorinated P(VDF-TrFE), high areal capacitance of > 4 µFcm-2 is reached thanks to the combined polarization of the -C-F interface dipoles and electrical double layers formation. To eliminate the integral complexity in differentiating field induced charge carriers from any possible carriers resulting from electrochemical doping of the semiconducting layer, we systematically measured the specific capacitance for each semiconductor/dielectric FET combination to avoid overestimation of the μFET extraction in our SEGI devices - a major common issue in several publications. For instance, with our engineered SEGIs, unprecedented hole mobility increase from ~10-2 to 5 cm2V-1s-1 (corresponding ~37 cm2V-1s-1 by commonly used method) at ≤ 2 V operation is reached in commercially available poly(3-hexylthiophene-2,5-diyl) (P3HT) FETs, and μFET exceeding 10 cm2V-1s-1 in others semiconductors.

Most current electronics manufacturing technologies utilise subtractive processing that is expensive, wasteful and energy intensive. Printed electronics is revolutionising the electronics industry by enabling additive processing that significantly reduces expense, waste and energy consumption. The EU-funded PLASMAS project demonstrates the capability of printed electronics based on novel nanoparticle Cu inks with favourable cost to performance ratios, through development of large area printed circuit boards and printed logic as well as OLED and OPV elements with printed Cu nanoparticle electrodes. However, a number of challenges need to be overcome when printing these metal nanoparticle inks – the typical feature height of printed structures of several 100 nm tend to exhibit a rough surface, which can lead to shorts in the device after subsequent overcoating of the organic active layer materials. Furthermore, the sintering temperature of the nanoparticle inks needs to be low (< 130 °C) in order to allow deposition and curing on transparent flexible substrates such as PET. 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 of the project highlight overall parameters for solution processing and implementation of novel metal nanoparticle materials and architectures in printed electronics.

Iron oxide nanoparticles (IONPs) are among the most promising candidates for nano-scale magnetic memory applications due to their excellent magnetic properties. The information can be stored depending on the magnetization of the particles. The general drawback of IONPs however 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 (thermal decomposition), wherein different synthesis parameters are surveyed and their effect on the particle size, stoichiometry of cobalt within the spinel ferrite nano crystals (CoxFe3-xO4) and magnetic properties are investigated. The synthesis was optimized to obtain sub-20 nm highly crystalline and monodisperse ferromagnetic nanoparticles with optimum magnetization and coercivity values. The particles were further modified by grafting polymerization from the surface of nanoparticles. Polymeric shells of different molecular weight are obtained, which allowed well dispersion of the ferromagnetic nanoparticles in common organic solvents. Nanoparticles can be solution processed to form a ferromagnetic thin-film. Solution processable magnetic films can open a new avenue in the 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.