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This paper introduces a linearized model of electrocaloric cooling. The model is derived for electrocaloric Brayton, Carnot, and Otto cycles, and a more practical hybrid constant voltage-charge (HCVC) variation of the Otto cycle. It is then parametrized for a benchmark terpolymer material. Model outputs are used to examine the system performance under each cycle as a function of temperature lift. The impact of electrical charge recovery efficiency on performance is then invesand to provide insight into system optimization requirements. Practical limitations of charge recovery circuits are discussed in the context of heat and work transfer in each cycle leg. Results indicate that electrical charge recovery efficiency greater than 95% is needed to achieve competitive system efficiency and that this is challenging with a Carnot cycle, despite its theoretical optimality. The Brayton and Otto cycles, in contrast, can achieve cooling efficiencies that approach the theoretical maximum.

A printed flexible hybrid electronics (FHE) technology platform is described, which combines a thin-film audio speaker, printed interconnects, and printed passive components in a highly flexible system. Bimorph piezoelectric polymer speaker structures were developed and shown to give increased loudness compared with a single layer speaker, with good fidelity and easily recognizable sound. Speakers were fabricated on flexible thin polyimide substrates, which enables integration with printed electronics and other thin-film devices. Two demonstrator circuits were designed to operate the speakers and were fabricated using printed FHE techniques. One circuit was an amplifier for a portable music player, and the second provides a record and playback function using an audio integrated circuit. The fabrication of these devices included ink-jet printed interconnects and ink-jet printed resistors, which showed a good long-term stability and flexibility.

Competitive cooling with capacitors Current large-scale cooling devices use vapor compression refrigeration. The efficiency of air conditioners has been optimized, but they can be noisy and rely on problematic greenhouse gases. Two groups now present designs for electrocaloric cooling using lead scandium tantalate capacitors that change temperature under an electric field. Y. Wang et al. obtained a very large heat flux using only solid materials and a cooling fan to remove heat from their device. Torello et al. used fluids for heat transfer, leading to a very large temperature difference between the hot side and the cold side. The new designs demonstrate the potential for devices that might be competitive with vapor compression–based appliances with further optimization. Science , this issue p. 129 , p. 125

In this paper, we combine high functionality c-Si CMOS and digitally printed components and interconnects to create an mostly printed integrated electronic system on a flexible substrate that can read and process multiple discrete sensors. Our approach is to create an integrated platform for the fabrication of mechanically flexible sensor tags that can be powered and interrogated wirelessly, precluding the need of a separate on-board power source. The high level system design is aimed at minimizing the number of non-printed components and reducing power consumption to enable energy harvesting from the RF field. Digital fabrication of these systems requires a range of materials, feature sizes, and electrical characteristics. In order to integrate the various printed components on a single substrate, we developed an integrated printer to accommodate a range of inks for printing the antenna, different types of sensors, chip interconnects, and wiring. For chip attachment to the flexible substrate, a method of integrating the die within the thickness of the substrate was developed. With proper system design and fabrication, a complete integrated tag for wireless sensing of temperature, strain, and touch was demonstrated. Our approach facilitates customization to a wide variety of sensors and user interfaces suitable for a broad range of applications including remote monitoring of health, structures, and the environment.

This paper presents two versions of a silicon mechanical heat switch designed for electrocaloric cooling. The first design, which consists of two 10-mm-by-12.8-mm micromachined silicon parts, allows investigation of the performance of a reciprocating solid thermal shunt device. This heat switch has a measured thermal contrast ratio in the range of 34-59. The second design adds self-alignment features that constrain the motion of the switch to facilitate fabrication and integration. The self-aligned heat switch has a thermal contrast ratio >28. It has been successfully operated for >18 000 cycles and employed in an electrocaloric cooler. Design, fabrication, and characterization of both heat switches are reported.

Printed organic electronics are being explored for a wide range of possible applications, with much of the current focus on smart labels, wearables, health monitoring, sensors and displays. These applications typically integrate various types of sensors and often include silicon integrated circuits (IC) for computation and wireless communications. Organic thin film transistors (TFT), particularly when printed, have performance and yield limitations that must be accommodated by the circuit design. The circuit design also needs to select sensor technology, ICs and other circuit elements to integrate with the TFTs and match the functional and performance requirements of the application. This paper describes organic TFT properties and strategies for circuit and sensor design, with examples from various sensor systems.

Wireless, battery-free, peel-and-stick sensors can enable many new capabilities in the Internet-of-Things(IoT). Low-cost sensor hardware and manufacturing together with no-skill installation and commissioning and low maintenance requirements can allow widely distributed sensors for continuous, comprehensive monitoring for structural health, physical health, safety, and industrial and environmental applications. This paper presents a system of RF-powered flexible sensors for building environment sensing with the potential to deliver up to 30% energy savings through improved HVAC controls. The system utilizes a set of electronic hubs that both provide remote power to the sensors and wirelessly relay sensor data to the building management system (BMS). The sensors are flexible electronic labels powered by rectified RF energy received from a hub and can contain multiple printed and conventional sensors including for temperature, humidity, and air quality. The electronic hub includes a programmable multidirectional beam-steering antenna that allows arbitrarily-placed sensors to be automatically located by the system through monitoring of received RF power as a function of transmission angle. The system has achieved extremely low-power operation, wireless sensor data transmission over > 10 meters, remote power delivered across >7 meters and sensor localization to within 0.5 meters.

Flexible electronics offers opportunities for greatly expanding the ability to probe the environment with distributed sensors that can be incorporated into the Internet of Things (IoT). This promise is embodied by “peel-and-stick” labels with advanced functionality that can be easily deployed on structures or the body and integrated into analytical systems. Recent progress in materials, devices, and fabrication techniques, together with everadvancing electronics capabilities has enabled the demonstration of new sensors and prototype systems that provide insight into the trajectory of this technology.

A systematic dispersion engineering approach is presented toward designing a III-nitride micro-resonator for a blue frequency comb. The motivation for this endeavor is to fill the need for compact, coherent, multi-wavelength photon sources that can be paired with, e.g., the 171Yb+ ion in a photonic integrated chip for optical sensing, time-keeping, and quantum computing applications. The challenge is to overcome the normal material dispersion exhibited by the otherwise ideal (i.e., low-loss and large-Kerr-coefficient) AlGaN family of materials, as this is a prerequisite for bright-soliton Kerr comb generation. The proposed approach exploits the avoided-crossing phenomenon in coupled waveguides to achieve strong anomalous dispersion in the desired wavelength range. The resulting designs reveal a wide range of dispersion response tunability, which is expected to allow access to the near-UV wavelength regime as well. Numerical simulations of the spatio-temporal evolution of the intra-cavity field under continuous-wave laser pumping confirm that such a structure is capable of generating a broadband blue bright-soliton Kerr frequency comb. The proposed micro-resonator heterostructure is amenable to the current state-of-the-art growth and fabrication methods for AlGaN semiconductors.

PARC, a Xerox Company, is developing a low-cost system of peel-and-stick wireless sensors that will enable widespread building environmental sensor deployment with the potential to deliver up to 30% energy savings. The system is embodied by a set of radio-frequency (RF) hubs that provide power to automatically located sensor nodes and relay data wirelessly to the building management system (BMS). The sensor nodes are flexible electronic labels powered by rectified RF energy transmitted by the RF hub and can contain multiple printed and conventional sensors. The system design overcomes limitations in wireless sensors related to power delivery, lifetime, and cost by eliminating batteries and photovoltaic devices. Sensor localization is performed automatically by the inclusion of a programmable multidirectional antenna array in the RF hub. Comparison of signal strengths as the RF beam is swept allows for sensor localization, reducing installation effort and enabling automatic recommissioning of sensors that have been relocated. PARC has already demonstrated wireless power and temperature data transmission up to a distance of 20 m with 71 s between measurements, using power levels well within the Federal Communications Commission regulation limits in the 902–928 MHz industrial, medical and scientific (ISM) band. The sensor's RF energy harvesting antenna achieves high performance with dimensions of 5 cm × 9.5 cm.

Printing as a manufacturing technique is a promising approach to fabricate low-cost, flexible, and large area electronics. Over the last two decades, a wide range of applications has been explored, among them displays, sensors, and printed radio-frequency identification devices. Some of these turned out to be challenging to commercialize due to the required infrastructure investment, accuracy or performance expectations compared to incumbent technologies. However, the progress in terms of material science, device, and process technology now makes it possible to target some realistic applications such as printed sensor labels. The journey leading to this exciting opportunity has been complex. This review describes the experience and current efforts in developing the technology at PARC, a Xerox Company. Printed smart labels open up low-cost solutions for tracking and sensing applications that require high volumes and/or would benefit from disposability. Examples include radiation tags, one-time use medical sensors, tracking the temperature of pharmaceuticals at the item level, and monitoring food sources for spoilage and contamination. Higher performance can be achieved with printed hybrid electronics, integrating microchip-based signal processing, wireless communication, sensing, multiplexing, as well as ancillary passive elements for low-profile microelectronic devices, opening up further applications. This technology offers custom circuitry for demanding applications and is complementary to mass printed transistor circuits. As an example, we describe a prototype sense-and-transmit system, focusing particularly on issues of integration, such as impedance matching between the sensor and circuits, robust printed interconnection of the chips, and compatible interface electronics between printed and discrete parts. Next-generation technologies will enable printing of entire smart systems using microchip inks. A new printing concept for the directed assembly of silicon microchips into functional circuits is described. The process is scalable and has the potential to enable additive, digital manufacturing of high-performance electronic systems.

© 2017 IOP Publishing Ltd. Printing is a promising manufacturing approach for the fabrication of flexible, large-area, custom sensor systems for applications such as wearable electronics and sensor labels. While printed examples of many physical and chemical sensors have been demonstrated, functionality useful for stand-alone systems such as high-resolution analog-to-digital conversion and wireless communication to address these sensors is not currently available in circuits printed entirely from solution. In order to retain the benefits of print manufacturing without sacrificing performance, a hybrid approach can be followed where printed and pre-fabricated devices are used together. In this report a mostly-printed wireless light and temperature sensor system that operates at 3.6 V and reports light and temperature readings wirelessly with a sensitivity of 0.7 °Cand 2.5 μWcm-2 at 500 nm respectively is demonstrated. The number of printed components was maximized and off-the-shelf microfabricated devices were only introduced where functionality is not currently achievable through printing. Onto a flexible polyester substrate, print processes were used to fabricate the bulk-heterojunction photodiode, thermistor, low-voltage operation multiplexing transistors, antenna, passives and interconnects, and silicon ICs are used for signal processing, memory and wireless communication. The printed components (sensors and transistors) were specifically developed to facilitate electrical integration into the hybrid system.

PARC, a Xerox Company, is developing a low-cost system of peel-and-stick wireless sensors that will enable widespread building environment sensor deployment with the potential to deliver up to 30% energy savings. The system is embodied by a set of RF hubs that provide power to automatically located sensor nodes, and relay data wirelessly to the building management system (BMS). The sensor nodes are flexible electronic labels powered by rectified RF energy transmitted by an RF hub and can contain multiple printed and conventional sensors. The system design overcomes limitations in wireless sensors related to power delivery, lifetime, and cost by eliminating batteries and photovoltaic devices. Sensor localization is performed automatically by the inclusion of a programmable multidirectional antenna array in the RF hub. Comparison of signal strengths while the RF beam is swept allows for sensor localization, reducing installation effort and enabling automatic recommissioning of sensors that have been relocated, overcoming a significant challenge in building operations. PARC has already demonstrated wireless power and temperature data transmission up to a distance of 20m with less than one minute between measurements, using power levels well within the FCC regulation limits in the 902–928 MHz ISM band. The sensor’s RF energy harvesting antenna achieves high performance with dimensions below 5cm × 9cm.

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.

We demonstrate an inkjet-printed organic thin-film transistor (OTFT) circuit for reading ferroelectric (FE) nonvolatile rewritable memories. With the large difference in polarization charge between FE memory states, we implement a single-OTFT gain stage with latch and show that a gain of −2.8 is sufficient to distinguish memory states. This paper evaluates the effect of device variations on the yield of this readout circuit.

Additive manufacturing and 3D printing are poised to reshape entire manufacturing value chains. To be truly disruptive, additive manufacturing has to move beyond shapes and colors. Novel printing technologies are beginning to emerge that enable conformal electronics and even printing with inks containing microchips. This in turn also creates new openings for the progress of electronics itself. Over the last 50 years silicon microelectronics advanced through shrinking device dimensions and packing more and more functionality into tiny spaces. Printing technologies open up exciting new ways of scaling electronics “Beyond Moore”, through the integration of micro and macro, creating new form factors, complex shapes, conformal devices and distributed systems. Printed, hybrid electronics systems will enable new classes of sensor systems, structural electronics and wearable devices, where the “system is the package”.

Printed organic thin-film transistor (OTFT) technology has the potential to enable ubiquitous, inexpensive, flexible electronic systems. Realization of this vision requires circuit design techniques sensitive to the constraints of the technology, as well as integration with components such as memory, sensors, and displays. The OTFT fabrication process is much less mature than silicon technologies, and direct implementation of conventional complementary designs is challenging due to the relatively low yield, high variability, and drift instability of printed OTFTs. Here we demonstrate an OTFT-specific approach to design with a pulse generator circuit for writing non-volatile thin-film ferroelectric (FE) memory. The approach takes into account the constraints of existing OTFT processes and can be extended to other circuits. The new circuit, and a more conventional complementary pulse-generator, are designed, fabricated, and tested in an additive ink-jet OTFT process.

Wireless sensing has broad applications in a wide variety of fields such as infrastructure monitoring, chemistry, environmental engineering and cold supply chain management. Further development of sensing systems will focus on achieving light weight, flexibility, low power consumption and low cost. Fully printed electronics provide excellent flexibility and customizability, as well as the potential for low cost and large area applications, but lack solutions for high-density, high-performance circuitry. Conventional electronics mounted on flexible printed circuit boards provide high performance but are not digitally fabricated or readily customizable. Incorporation of small silicon dies or packaged chips into a printed platform enables high performance without compromising flexibility or cost. At PARC, we combine high functionality c-Si CMOS and digitally printed components and interconnects to create an integrated platform that can read and process multiple discrete sensors. Our approach facilitates customization to a wide variety of sensors and user interfaces suitable for a broad range of applications including remote monitoring of health, structures and environment. This talk will describe several examples of printed wireless sensing systems. The technologies required for these sensor systems are a mix of novel sensors, printing processes, conventional microchips, flexible substrates and energy harvesting power solutions.

In electronic systems, components often require different supply voltage for operation. In order to meet this requirement and to optimize power consumption for flexible electronics, we demonstrate a pulsed voltage multiplier that boosts the voltage at specific circuit nodes above the supply voltage. A five-stage pulsed voltage multiplier is shown to provide an output voltage up to 18 V from a supply voltage of 10 V, with minimum 10 ms pulse rise time for a 70 pF load. A key requirement for the pulsed voltage multiplier circuit is low device leakage to boost the output voltage level. To minimize leakage, the composition of the organic semiconducting layer is modified by blending an insulating polymer with the small molecule semiconductor. This modification allows control over the transistor turn-on voltage, which enables low leakage current required for operation of the circuits. The printed multiplier allows a single power source to deliver multiple voltage levels and enables integration of lower voltage logic with components that require higher operating voltage, for example, in the case of recording data into memory cells in sensor tags.

We have demonstrated a printed electronic tag that monitors time-integrated sensor signals and writes to nonvolatile memories for later readout. The tag is additively fabricated on flexible plastic foil and comprises a thermistor divider, complementary organic circuits and two nonvolatile memory cells. With a supply voltage below 30 V, the threshold temperatures can be tuned between 0 °C and 80 °C. The time-temperature dose measurement is calibrated for minute-scale integration. The two memory bits are sequentially written in a thermometer code to provide an accumulated dose record.

Dynamic and static shift-register circuits are fabricated with an inkjet process for printing complementary organic semiconductors. The static design is based on edge-triggered master-slave flip-flops, and the dynamic design is based on a true-single-phase-clock architecture. The merits and drawbacks of the two approaches are considered and compared.

Digital, additive printing of electronic materials allows rapid, highly customizable fabrication, and low-cost printed electronics are compelling for internet-of-things applications that require large volume of distributed devices, such as in sensor networks and smart packaging. The functionalities required of the embedded devices will vary over a broad spectrum from simple passive tags to powerful microprocessor controllers. In our prototype development, we apply two progressive printing approaches: simple systems are inkjet printed entirely from solution electronic inks, whereas more complex functions are met by printing interconnects between silicon ICs and printed passive components, to combine the advantages of flexible printed devices with the high performance of silicon chips.

PARC and UCSD are developing a flexible hybrid biosensor platform to enable continuous remote monitoring of bioanalyte concentrations in saliva. The electrochemical sensor system will be fabricated on a small, flexible plastic foil for mounting on a mouth guard, and enable continuous sensing of lactate, glucose, or other analytes. Chronoamperometry based on enzymatic oxidation of target species has been demonstrated to have high sensitivity and capability for quantification of analyte concentrations. Saliva is favorable for biosensing because of its accessibility and the correlation with blood concentrations of important analytes. The goal of the current work is to demonstrate a manufacturable, reliable sensor system. To this end, the electronics will be fully encapsulated and include wireless charging and readout, with easily removable and replaceable printed electrodes. Here, we will present an overview of the system and discuss current progress.

PARC and NASA Ames have developed part-per-million level sensitivity room-temperature printed gas sensors based on arrays of modified single-walled carbon nanotubes (SWNTs). The SWNT sensors change resistance in response to reversible electro-chemical interactions between target analytes and the modifications on the SWNTs. The ultra-low power (microwatt level) ability to measure trace-gas concentrations through changes in SWNT resistance has enabled us to build an autonomous, off-the-grid, distributed gas sensing network to be deployed to the ARPA-E natural gas leak testing facility in Ft. Collins, CO during the spring of 2017. During this deployment, the leak detection network will be subjected to tests of its accuracy and precision in locating the sources of leaks on a mock natural gas well-pad. The key enablers of this technology are the SWNTs which we have modified with coatings, chemical functionalization, and nanoparticles, to achieve sensitivity to a wide selection of gases including CH4, NH3, CO, H2S, etc., in the presence of real-world environmental conditions. We will report on the results of this field deployment, along with a discussion of the SWNT modifications made to create the sensor arrays.

Two types of printable conductor and a bilayer gate dielectric are evaluated for use in all-additive, inkjetprinted complementary OTFTs. The Ag nanoparticle ink based on nonpolar alkyl amine surfactant or stabilizer enables good charge injection into p-channel devices, but this ink also leaves residual stabilizer that modifies the transistor backchannel and shifts the turn-on voltage to negative values. The Ag ink based on polar solvent requires dopant modification to improve charge injection to p-channel devices, but this ink allows the OTFT turn-on voltage to be close to 0 V. The reverse trend is observed for n-channel OTFTs. For gate insulator, a bilayer dielectric is demonstrated that combines the advantages of two types of insulator materials, in which a fluoropolymer reduces dipolar disorder at the semiconductor-dielectric interface, while a high-k PVDF terpolymer dielectric facilitates high gate capacitance. The dielectric is incorporated into an inverter and a three-stage ring oscillator, and the resulting circuits were demonstrated to operate at a supply voltage as low as 2 V, with bias stress levels comparable to circuits with other types of dielectrics.

PARC is developing extremely sensitive room-temperature printed gas sensors based on arrays of modified carbon nanotubes (CNTs). The sensors are combined with electronics to form distributed gas sensing networks for applications including natural gas leak detection, equipment failure, industrial safety, and indoor air quality monitoring. The sensing materials comprise CNTs modified with coatings, chemical functionalization, and nanoparticles, to achieve sensitivity to a wide selection of gases including CH4, NH3, CO, H2S, and others. Advanced machine learning techniques allow gas identification and sub-ppm sensitivity. Digital printing of sensor materials on printed electrodes enables low-cost, simple customization of sensor design, and electrode layout. An overview of the project and recent experimental results will be presented.

Scalable circuits of organic logic and memory are realized using all-additive printing processes. A 3-bit organic complementary decoder is fabricated and used to read and write non-volatile, rewritable ferroelectric memory. The decoder-memory array is patterned by inkjet and gravure printing on flexible plastics. Simulation models for the organic transistors are developed, enabling circuit designs tolerant of the variations in printed devices. We explain the key design rules in fabrication of complex printed circuits and elucidate the performance requirements of materials and devices for reliable organic digital logic.

The thermoelectric generator (TEG) is the predominant compact, solid-state heat engine. Effective utilization of a heat resource using a TEG requires maximizing its power output by interposing a regulated power converter between the source and load. In this work, a maximum-powerpoint-tracking system architecture is introduced that is compatible with efficient pulse-width modulated converter topologies. The control system, based on input voltage sampling, does not require a microcontroller or analog-to-digital converter and can be built with available discrete components. Measurement results of a demonstration SEPIC converter are presented, validating the concept.

To enable the integration of components with different supply voltage requirements, and to optimize power consumption in printed flexible electronics, we demonstrate an inkjet-printed pulsed voltage multiplier that boosts the voltage at specific circuit nodes above the supply voltage. A five-stage pulsed voltage multiplier is shown to provide an output voltage up to 18 V from a supply voltage of 10 V, with minimum 10 ms pulse rise time for a 70 pF load. This circuit allows a single power source to deliver multiple voltage levels and enables integration of low-voltage logic with components that require higher operating voltage. A key requirement for the pulsed voltage multiplier circuit is low device leakage to boost the output voltage level. To this end, the composition of the transistor semiconducting layer is modified by blending an insulating polymer with the small molecule semiconductor. This modification allows control over the transistor turn-on voltage, which enables low leakage current required for operation of the circuit.

We describe the design, characterization, and demonstration of a fully integrated single-photon avalanche diode (SPAD) imager for use in time-resolved fluorescence imaging. The imager consists of a 64-by-64 array of active SPAD pixels and an on-chip time-to-digital converter (TDC) based on a delay-locked loop (DLL) and calibrated interpolators. The imager can perform both standard time-correlated single-photon counting (TCSPC) and an alternative gated-window detection useful for avoiding pulse pile-up when measuring bright signal levels. To illustrate the use of the imager, we present measurements of the decay lifetimes of fluorescent dyes of several types with a timing resolution of 350 ps.

We present an active oligonucleotide microarray platform for time-resolved Forster-resonance-energy-transfer (TR-FRET) assays. In these assays, immobilized probe is labeled with a donor fluorophore and analyte target is labeled with a fluorescence quencher. Changes in the fluorescence decay lifetime of the donor are measured to determine the extent of hybridization. In this work, we demonstrate that TR-FRET assays have reduced sensitivity to variances in probe surface density compared with standard fluorescence-based microarray assays. Use of an active array substrate, fabricated in a standard complementary metal-oxide-semiconductor (CMOS) process, provides the additional benefits of reduced system complexity and cost. The array consists of 4096 independent single-photon avalanche diode (SPAD) pixel sites and features on-chip time-to-digital conversion. We demonstrate the functionality of our system by measuring a DNA target concentration series using TR-FRET with semiconductor quantum dot donors.

A heat-switch-based electrocaloric cooler is reported in this letter. The device consists of two silicon heat switches and an electrocaloric module based on BaTO3 multilayer capacitors (MLCs). To operate the cooler, the heat switches are actuated synchronously with the application of electric fields across the MLCs. Heat flux versus temperature lift is fully characterized. With an electric field strength of 277 kV/cm, the system achieves a maximum heat flux of 36 mW and maximum temperature lift of greater than 0.3 °C, close to the expected MLC adiabatic temperature change of 0.5 °C. The cooler is shown to work reliably over thousands of actuation cycles.

Realization of the potential of electrocaloric heat pumps includes consideration of not only material properties but also device characteristics and cycle operation. We present detailed models and analysis that elucidate the key parameters for performance optimization. We show that the temperature lift, cooling power, and efficiency of a system driven by heat switches depend on system operating conditions and the combined thermal properties of both the heat switches and the electrocaloric capacitor. We show experimental results that validate the models and draw conclusions about building high-performance systems.

Hydrogen production via photoelectrochemical (PEC) water splitting has promise for storage of solar energy in a clean fuel for vehicular and grid applications. However, PEC technologies with high solar-to-hydrogen (STH) efficiency have high materials and processing costs, and less expensive alternatives have not achieved high efficiencies. Here we discuss a systems-level approach to improving utilization of high-efficiency III-V PEC cells using optical concentration factors much higher than have been previously considered. Full system and cost analyses are presented, indicating the potential of this approach to reduce the cost per kilogram of hydrogen produced to significantly lower than that of a photovoltaic-plus-electrolyzer solution.

Inkjet printing on pre-fabricated high-resolution substrate is developed to improve the operational speed of printed organic transistors. The high-resolution features are designed to define transistor critical dimensions, while maintaining the flexibility to incorporate different circuit constructions. Logic gate and ring oscillator circuits fabricated by inkjet printing on the high-resolution substrate are demonstrated, to show that the same high resolution pattern can be adapted for constructing different electronic circuits.

Mechanically flexible arrays of alkaline electrochemical cells fabricated using stencil printing onto fibrous substrates are shown to provide the necessary performance characteristics for driving ink-jet printed circuits. Due to the dimensions and material set currently required for reliable low-temperature print processing of electronic devices, a battery potential greater than that sourced by single cells is typically needed. The developed battery is a series interconnected array of 10 low resistance Zn-MnO2 alkaline cells, giving an open circuit potential of 14 V. This flexible battery is used to power an ink-jet printed 5-stage complementary ring oscillator based on organic semiconductors.