Solution-based self-aligned hybrid organic/metal-oxide complementary logic with megahertz operation

We have developed a novel solution-based integration scheme featuring organic and metal-oxide semiconductors with a polymeric gate dielectric. The integration relies on a facile subtractive patterning technique for the semiconductors, which, through the selection of an appropriate etch stopper, leads to ideal transistor performance. We utilized this novel integration scheme to fabricate self-aligned transistors and logic circuits with a high-mobility p-type conjugated polymer and an n-type amorphous oxide semiconductor, along with a composite polymeric gate dielectric, all solution-deposited by spin coating. The resulting complementary logic gates are capable of rail-to-rail transitions, low-voltage operation down to a 3.5 V power supply, and ample noise margins. Thanks to the self-aligned-gate approach and the state-of-the-art balanced mobilities of the selected semiconductors, our logic gates achieve megahertz operation, thus demonstrating the strength of our hybrid integration scheme.We gratefully acknowledge Mike Hurhangee and Iain McCulloch of Imperial College for supplying the IDT-BT conjugated polymer. We also acknowledge financial support from the European Commission through the POINTS project (FP7-NMP- 2010-Small-4).This is the author accepted manuscript. The final version is available via Elsevier at http://www.sciencedirect.com/science/article/pii/S1566119915000956

Lead-free halide perovskite photovoltaics: Challenges, open questions, and opportunities

In recent years, lead-free metal-halide perovskite photovoltaics has attracted ever-growing attention, in view of its potential to replicate the outstanding properties of lead-halide perovskite photovoltaics, but without the toxicity burden of the latter. Despite a research effort much smaller in scale than that pursued with lead-based perovskites, considerable progress has been achieved in lead-free perovskite photovoltaics, with the highest power conversion efficiencies now being in the region of 13%. In this Perspective, we first discuss the state of the art of lead-free perovskite photovoltaics and additionally highlight promising directions and strategies that could lead to further progress in material exploration and understanding as well as in photovoltaic efficiency. Furthermore, we point out the widespread lack of experimental data on the fundamental optoelectronic properties of lead-free halide perovskite absorbers (e.g., charge carrier mobility, defect parameters, Urbach energy, and the impact of dimensionality). All of this currently hampers a rational approach to further improving their performance and points to the need for a concerted effort that could bridge this knowledge gap. Additionally, this Perspective brings to the fore the manifold photovoltaic opportunities—thus far largely unexplored with lead-free perovskite absorbers—beyond single-junction outdoor photovoltaics, which may potentially enable the realization of their full potential. The exploration of these opportunities (tandem photovoltaics, indoor photovoltaics, and building-integrated and transparent photovoltaics) could energize the investigation of existing and new classes of lead-free perovskite absorbers beyond current paradigms and toward high photovoltaic performance.</jats:p

Programmable logic circuits for functional integrated smart plastic systems

In this paper, we present a functional integrated plastic system. We have fabricated arrays of organic thin-film transistors (OTFTs) and printed electronic components driving an electrophoretic ink display up to 70mm by 70mm on a single flexible transparent plastic foil. Transistor arrays were quickly and reliably configured for different logic functions by an additional process step of inkjet printing conductive silver wires and poly(3,4ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) resistors between transistors or between logic blocks. Among the circuit functions and features demonstrated on the arrays are a 7-stage ring oscillator, a D-type ip-flop memory element, a 2:4 demultiplexer, a programmable array logic device (PAL), and printed wires and resistors. Touch input sensors were also printed, thus only external batteries were required for a complete electronic subsystem. The PAL featured 8 inputs, 8 outputs, 32 product terms, and had 1260 p-type polymer transistors in a 3-metal process using diode-load logic. To the best of our knowledge, this is the first time that a PAL concept with organic transistors has been demonstrated, and also the first time that organic transistors have been used as the control logic for a flexible display which have both been integrated on to a single plastic substrate. The versatility afforded by the additive inkjet printing process is well suited to organic programmable logic on plastic substrates, in effect, making flexible organic electronics more flexibleRCUK, OtherThis is the final published version. It is also available from Elsevier at http://www.sciencedirect.com/science/article/pii/S1566119914003607#

Programmable logic circuits for functional integrated smart plastic systems

In this paper, we present a functional integrated plastic system. We have fabricated arrays of organic thin-film transistors (OTFTs) and printed electronic components driving an electrophoretic ink display up to 70 mm by 70 mm on a single flexible transparent plastic foil. Transistor arrays were quickly and reliably configured for different logic functions by an additional process step of inkjet printing conductive silver wires and poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) resistors between transistors or between logic blocks. Among the circuit functions and features demonstrated on the arrays are a 7-stage ring oscillator, a D-type flip-flop memory element, a 2:4 demultiplexer, a programmable array logic device (PAL), and printed wires and resistors. Touch input sensors were also printed, thus only external batteries were required for a complete electronic subsystem. The PAL featured 8 inputs, 8 outputs, 32 product terms, and had 1260 p-type polymer transistors in a 3-metal process using diode-load logic. To the best of our knowledge, this is the first time that a PAL concept with organic transistors has been demonstrated, and also the first time that organic transistors have been used as the control logic for a flexible display which have both been integrated on to a single plastic substrate. The versatility afforded by the additive inkjet printing process is well suited to organic programmable logic on plastic substrates, in effect, making flexible organic electronics more flexible. Crown Copyright (C) 2014 Published by Elsevier B.V.X113426Ysciescopu

Inkjet-Printed Nanocavities on a Photonic Crystal Template

The last decade has witnessed the rapid development of inkjet printing as an attractive bottom-up microfabrication technology due to its simplicity and potentially low cost. The wealth of printable materials has been key to its widespread adoption in organic optoelectronics and biotechnology. However, its implementation in nanophotonics has so far been limited by the coarse resolution of conventional inkjet-printing methods. In addition, the low refractive index of organic materials prevents the use of “soft-photonics” in applications where strong light confinement is required. This study introduces a hybrid approach for creating and fine tuning high-Q nanocavities, involving the local deposition of an organic ink on the surface of an inorganic 2D photonic crystal template using a commercially available high-resolution inkjet printer. The controllability of this approach is demonstrated by tuning the resonance of the printed nanocavities by the number of printer passes and by the fabrication of photonic crystal molecules with controllable splitting. The versatility of this method is evidenced by the realization of nanocavities obtained by surface deposition on a blank photonic crystal. A new method for a free-form, high-density, material-independent, and high-throughput fabrication technique is thus established with a manifold of opportunities in photonic applications.Part of this work was performed using the Darwin Supercomputer of the University of Cambridge High Performance Computing Service (http://www.hpc.cam.ac.uk/), provided by Dell Inc. using Strategic Research Infrastructure Funding from the Higher Education Funding Council for England and funding from the Science and Technology Facilities Council. V.P. gratefully acknowledges financial support from the United Kingdom Engineering and Physical Sciences Research Council (EPSRC) through the Centre for Innovative Manufacturing in Large Area Electronics (CIMLAE, program grant EP/K03099X/1) and the project Integration of Printed Electronics with Silicon for Smart sensor systems (iPESS). V.P. also acknowledges financial support from the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD) and the Collaborative Innovation Center of Suzhou Nano Science and Technology

Assessing the Impact of Defects on Lead-Free Perovskite-Inspired Photovoltaics via Photoinduced Current Transient Spectroscopy

Funder: Collaborative Innovation Center of Suzhou Nano Science & TechnologyFunder: Priority Academic Program Development of Jiangsu Higher Education Institutions; Id: http://dx.doi.org/10.13039/501100012246Funder: 111 Project; Id: http://dx.doi.org/10.13039/501100013314Funder: Joint International Research Laboratory of Carbon‐Based Functional Materials and DevicesThe formidable rise of lead-halide perovskite photovoltaics has energized the search for lead-free perovskite-inspired materials (PIMs) with related optoelectronic properties but free from toxicity limitations. The photovoltaic performance of PIMs closely depends on their defect tolerance. However, a comprehensive experimental characterization of their defect-level parameters—concentration, energy depth, and capture cross-section—has not been pursued to date, hindering the rational development of defect-tolerant PIMs. While mainstream, capacitance-based techniques for defect-level characterization have sparked controversy in lead-halide perovskite research, their use on PIMs is also problematic due to their typical near-intrinsic character. This study demonstrates on four representative PIMs (Cs3Sb2I9, Rb3Sb2I9, BiOI, and AgBiI4) for which Photoinduced Current Transient Spectroscopy (PICTS) offers a facile, widely applicable route to the defect-level characterization of PIMs embedded within solar cells. Going beyond the ambiguities of the current discussion of defect tolerance, a methodology is also presented to quantitatively assess the defect tolerance of PIMs in photovoltaics based on their experimental defect-level parameters. Finally, PICTS applied to PIM photovoltaics is revealed to be ultimately sensitive to defect-level concentrations <1 ppb. Therefore, this study provides a versatile platform for the defect-level characterization of PIMs and related absorbers, which can catalyze the development of green, high-performance photovoltaics.Royal Academy of Engineerin

Emerging Indoor Photovoltaic Technologies for Sustainable Internet of Things

The Internet of Things (IoT) provides everyday objects and environments with 'intelligence' and data connectivity, thereby holding significant promise to improve the quality of life as well as the efficiency of a wide range of human activities. However, the ongoing exponential growth of the IoT device ecosystem—up to tens of billions of units to date—poses a key sustainability challenge regarding how to power such devices. This Progress Report first discusses how energy harvesting can address this challenge. It then examines how indoor photovoltaics (IPV) constitutes an attractive energy harvesting solution, given its deployability, reliability, and power density. For IPV to provide an eco-friendly route to powering IoT devices, however, it is crucial that its underlying materials and fabrication processes are low-toxicity and not harmful to the environment over the product life cycle. A range of IPV technologies—both incumbent and emerging—developed to date are therefore discussed, with an emphasis on their environmental sustainability. Finally, IPV based on emerging lead-free perovskite-inspired absorbers are examined, highlighting their status and prospects for low-cost, durable, and efficient energy harvesting that is not harmful to the end user and environment. By examining emerging avenues for eco-friendly IPV, this Progress Report provides timely insight into promising directions toward IPV that can sustainably power the IoT revolution.EP/P027628/1 EU funding from H2020 project 1D-NEO

Emerging Indoor Photovoltaic Technologies for Sustainable Internet of Things

The Internet of Things (IoT) provides everyday objects and environments with “intelligence” and data connectivity to improve quality of life and the efficiency of a wide range of human activities. However, the ongoing exponential growth of the IoT device ecosystem—up to tens of billions of units to date—poses a challenge regarding how to power such devices. This Progress Report discusses how energy harvesting can address this challenge. It then discusses how indoor photovoltaics (IPV) constitutes an attractive energy harvesting solution, given its deployability, reliability, and power density. For IPV to provide an eco-friendly route to powering IoT devices, it is crucial that its underlying materials and fabrication processes are low-toxicity and not harmful to the environment over the product life cycle. A range of IPV technologies—both incumbent and emerging—developed to date is discussed, with an emphasis on their environmental sustainability. Finally, IPV based on emerging lead-free perovskite-inspired absorbers are examined, highlighting their status and prospects for low-cost, durable, and efficient energy harvesting that is not harmful to the end user and environment. By examining emerging avenues for eco-friendly IPV, timely insight is provided into promising directions toward IPV that can sustainably power the IoT revolution

Ambipolar carbon nanotube transistors with hybrid nanodielectric for low-voltage cmos-like electronics

Abstract The proliferation of place-and-forget devices driven by the exponentially-growing Internet of Things industry has created a demand for low-voltage thin-film transistor (TFT) electronics based on solution-processible semiconductors. Amongst solution-processible technologies, TFTs based on semiconducting single-walled carbon nanotubes (sc-SWCNTs) are a promising candidate owing to their comparatively high current driving capability in their above-threshold region at low voltages, which is desirable for applications with constraints on supply voltage and switching speed. Low-voltage above-threshold operation in sc-SWCNTs is customarily achieved by using high-capacitance-density gate dielectrics such as metal-oxides fabricated via atomic layer deposition (ALD) and ion-gels. These are unattractive, as ALD requires complex-processing or exotic precursors, while ion-gels lead to slower devices with poor stability. This work demonstrates the fabrication of low-voltage above-threshold sc-SWCNTs TFTs based on a high-capacitance-density hybrid nanodielectric, which is composed of a readily-made AlO x nanolayer and a solution-processed self-assembled monolayer (SAM). The resultant TFTs can withstand a gate-channel voltage of 1–2 V, which ensures their above-threshold operation with balanced ambipolar behavior and electron/hole mobilities of 7 cm2 V−1 s−1. Key to achieving balanced ambipolarity is the mitigation of environmental factors via the encapsulation of the devices with an optimized spin-on polymer coating, which preserves the inherent properties of the sc-SWCNTs. Such balanced ambipolarity enables the direct implementation of CMOS-like circuit configurations without the use of additional dopants, semiconductors or source/drain electrode metals. The resultant CMOS-like inverters operate in the above-threshold region with supply voltages in the 1–2 V range, and have positive noise margins, gain values surpassing 80 V/V, and a bandwidth exceeding 100 kHz. This reinforces SAM-based nanodielectrics as an attractive route to easy-to-fabricate sc-SWCNT TFTs that can operate in the above-threshold region and that can meet the demand for low-voltage TFT electronics requiring moderate speeds and higher driving currents for wearables and sensing applications.The authors acknowledge financial support from the National Natural Science Foundation of China (61950410619, 61950410759, 61805166, 61750110517 and 61874132), the Jiangsu Province Natural Science Foundation (BK20170345), and National Key Research and Development Program of China (2016YFB0401100). Additionally, this work is supported by the Collaborative Innovation Center of Suzhou Nano Science & Technology, the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD), the 111 Project, the Joint International Research Laboratory of Carbon-Based Functional Materials and Devices, the Engineering and Physical Sciences Research Council (Impact Acceleration Account res. grant no. 90413, Centre for Innovative Manufacturing in Large-Area Electronics EP/K03099X/1), and the EU H2020 Project No. 685758 “1DNEON”