Improving the long-term stability of perovskite solar cells is critical to the deployment of this technology. Despite the great emphasis laid on stability-related investigations, publications lack consistency in experimental procedures and parameters reported. It is therefore challenging to reproduce and compare results and thereby develop a deep understanding of degradation mechanisms. Here, we report a consensus between researchers in the field on procedures for testing perovskite solar cell stability, which are based on the International Summit on Organic Photovoltaic Stability (ISOS) protocols. We propose additional procedures to account for properties specific to PSCs such as ion redistribution under electric fields, reversible degradation and to distinguish ambient-induced degradation from other stress factors. These protocols are not intended as a replacement of the existing qualification standards, but rather they aim to unify the stability assessment and to understand failure modes. Finally, we identify key procedural information which we suggest reporting in publications to improve reproducibility and enable large data set analysis. Reliability of stability data for perovskite solar cells is undermined by a lack of consistency in the test conditions and reporting. This Consensus Statement outlines practices for testing and reporting stability tailoring ISOS protocols for perovskite devices.

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Consensus statement for stability assessment and reporting for perovskite photovoltaics based on ISOS procedures

Textiles have been concomitant of human civilization for thousands of years. With the advances in chemistry and materials, integrating textiles with energy harvesters will provide a sustainable, environmentally friendly, pervasive, and wearable energy solution for distributed on-body electronics in the era of Internet of Things. This article comprehensively and thoughtfully reviews research activities regarding the utilization of smart textiles for harvesting energy from renewable energy sources on the human body and its surroundings. Specifically, we start with a brief introduction to contextualize the significance of smart textiles in light of the emerging energy crisis, environmental pollution, and public health. Next, we systematically review smart textiles according to their abilities to harvest biomechanical energy, body heat energy, biochemical energy, solar energy as well as hybrid forms of energy. Finally, we provide a critical analysis of smart textiles and insights into remaining challenges and future directions. With worldwide efforts, innovations in chemistry and materials elaborated in this review will push forward the frontiers of smart textiles, which will soon revolutionize our lives in the era of Internet of Things.

Smart Textiles for Electricity Generation.

The performance and integration density of silicon integrated circuits (ICs) have progressed at an unprecedented pace in the past 60 years. While silicon ICs thrive at low-power high-performance computing, creating flexible and large-area electronics using silicon remains a challenge. On the other hand, flexible and printed electronics use intrinsically flexible materials and printing techniques to manufacture compliant and large-area electronics. Nonetheless, flexible electronics are not as efficient as silicon ICs for computation and signal communication. Flexible hybrid electronics (FHE) leverages the strengths of these two dissimilar technologies. It uses flexible and printed electronics where flexibility and scalability are required, i.e., for sensing and actuating, and silicon ICs for computation and communication purposes. Combining flexible electronics and silicon ICs yields a very powerful and versatile technology with a vast range of applications. Here, the fundamental building blocks of an FHE system, printed sensors and circuits, thinned silicon ICs, printed antennas, printed energy harvesting and storage modules, and printed displays, are discussed. Emerging application areas of FHE in wearable health, structural health, industrial, environmental, and agricultural sensing are reviewed. Overall, the recent progress, fabrication, application, and challenges, and an outlook, related to FHE are presented.

A New Frontier of Printed Electronics: Flexible Hybrid Electronics.

The programmable nature of smart textiles makes them an indispensable part of an emerging new technology field. Smart textile-integrated microelectronic systems (STIMES), which combine microelectronics and technology such as artificial intelligence and augmented or virtual reality, have been intensively explored. A vast range of research activities have been reported. Many promising applications in healthcare, the internet of things (IoT), smart city management, robotics, etc., have been demonstrated around the world. A timely overview and comprehensive review of progress of this field in the last five years are provided. Several main aspects are covered: functional materials, major fabrication processes of smart textile components, functional devices, system architectures and heterogeneous integration, wearable applications in human and nonhuman-related areas, and the safety and security of STIMES. The major types of textile-integrated nonconventional functional devices are discussed in detail: sensors, actuators, displays, antennas, energy harvesters and their hybrids, batteries and supercapacitors, circuit boards, and memory devices.

Smart Textile-Integrated Microelectronic Systems for Wearable Applications

In recent years, wearable electronics have experienced tremendous development due to their promising applications in fields such as portable, flexible/stretchable human-interactive sensors, displays, and energy devices. To effectively fabricate wearable electronics, a high-efficient, cost-saving, and eco-friendly manufacture technology is required. Inkjet printing, which rapidly, precisely, and reproducibly deposits a broad variety of functional materials in a non-impact, addictive patterning, and maskless approach, serves as an effective tool for the fabrication of wearable electronics. In this review, the recent advances in inks, strategies, and the applications of inkjet-printed wearable electronics are summarized. Based on uniform and high-resolution patterns, well-compatible functional inks can be deposited to fabricate flexible/stretchable and durable wearable electronics. Perspectives on the remaining challenges and future developments are also proposed.

Inkjet printing wearable electronic devices

This letter introduces a new technique of inkjet printing antennas on textiles. A screen-printed interface layer was used to reduce the surface roughness of the polyester/cotton material that facilitated the printing of a continuous conducting surface. Conducting ink was used to create three inkjet-printed microstrip patch antennas. An efficiency of 53% was achieved for a fully flexible antenna with two layers of ink. Measurements of the antennas bent around a polystyrene cylinder indicated that a second layer of ink improved the robustness to bending.

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Inkjet-Printed Microstrip Patch Antennas Realized on Textile for Wearable Applications

This study presents an inkjet printed textile antenna realised using a novel fabrication methodology. Conventionally, it is very difficult to inkjet print onto textiles because of surface roughness. This study demonstrates how this can be overcome by developing an interface coated layer which bonds to a standard polyester cotton fabric, creating a smooth surface. A planar dipole antenna has been fabricated, simulated and measured. This study includes DC resistance, RF reflection coefficient results and antenna radiation patterns. Efficiencies of greater than 60% have been achieved with only one layer of conducting ink. The study demonstrates that the interface layer saves considerable time and cost in terms of the number of inkjet layers needed whilst also improving the printing resolution.

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Inkjet printed dipole antennas on textiles for wearable communications

This paper presents a flexible 2.45-GHz wireless power harvesting wristband that generates a net dc output from a −24.3-dBm RF input. This is the lowest reported system sensitivity for systems comprising a rectenna and impedance-matching power management. A complete system has been implemented comprising: a fabric antenna, a rectifier on rigid substrate, a contactless electrical connection between rigid and flexible subsystems, and power electronics impedance matching. Various fabric and flexible materials are electrically characterized at 2.45 GHz using the two-line and the T-resonator methods. Selected materials are used to design an all-textile antenna, which demonstrates a radiation efficiency above 62% on a phantom irrespective of location, and a stable radiation pattern. The rectifier, designed on a rigid substrate, shows a best-in-class efficiency of 33.6% at −20 dBm. A reliable, efficient, and wideband contactless connection between the fabric antenna and the rectifier is created using broadside-coupled microstrip lines, with an insertion loss below 1 dB from 1.8 to over 10 GHz. A self-powered boost converter with a quiescent current of 150 nA matches the rectenna output with a matching efficiency above 95%. The maximum end-to-end efficiency is 28.7% at −7 dBm. The wristband harvester demonstrates net positive energy harvesting from −24.3 dBm, a 7.3-dB improvement on the state of the art.

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A Flexible 2.45-GHz Power Harvesting Wristband With Net System Output From −24.3 dBm of RF Power

The effect of the type of illumination on the energy harvesting performance of solar cells

A novel technique for inkjet printing frequency selective surfaces (FSSs) on textiles is introduced. The challenge of printing an inkjet layer of 3 μm thickness on polyester cotton with a surface roughness of the order of 150 μm is achieved with a screen-printed interface layer. The conducting inkjet layer is then printed directly on top of the interface layer. A screen mask was used so that the interface layer was only printed directly below the conducting ink. A square FSS structure has been fabricated and the measured shielding has been compared to simulations.

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Yi Li

Papers

Inkjet-Printed Microstrip Patch Antennas Realized on Textile for Wearable Applications

Inkjet printed dipole antennas on textiles for wearable communications

A Flexible 2.45-GHz Power Harvesting Wristband With Net System Output From −24.3 dBm of RF Power

The effect of the type of illumination on the energy harvesting performance of solar cells

Printed frequency selective surfaces on textiles