Nacre-inspired MXene-based film for highly sensitive piezoresistive sensing over a broad sensing range

As the main component of wearable electronic equipment,flexible pressure sensors have attracted wide attention due to their excellent sensitivity and their promise with respect to applications in health monitoring,electronic skin,and human-computer interactions.However,it remains a significant challenge to achieve epidermal sensing over a wide sensing range,with short response/recovery time and featuring seamless conformability to the skin simultaneously.This is critical since the capture of minute electrophysiological signals is important for health care applications.In this paper,we report the preparation of a nacre-like MXene/sodium carboxymethyl cellulose(CMC)nanocomposite film with a“brick-and-mortar”interior structure using a vacuum-induced self-assembly strategy.The synergistic behavior of the MXene“brick”and flexible CMC“mortar”contributes to attenuating interlamellar self-stacking and creates numerous variable conductive pathways on the sensing film.This resulted in a high sensitivity over a broad pressure range(i.e.,0.03-22.37 kPa:162.13 kPa^(-1);22.37-135.71 kPa:127.88 kPa^(-1);135.71-286.49 kPa:100.58 kPa^(-1)).This sensor also has a low detection limit(0.85 Pa),short response/recovery time(8.58 ms/34.34 ms),and good stability(2000 cycles).Furthermore,we deployed pressure sensors to distinguish among tiny particles,various physiological signals of the human body,space arrays,robot motion monitoring,and other related applications to demonstrate their feasibility for a variety of health and motion monitoring use cases.

Morphological Engineering of Sensing Materials for Flexible Pressure Sensors and Artificial Intelligence Applications

As an indispensable branch of wearable electronics,flexible pressure sensors are gaining tremendous attention due to their extensive applications in health monitoring,human-machine interaction,artificial intelligence,the internet of things,and other fields.In recent years,highly flexible and wearable pressure sensors have been developed using various materials/structures and transduction mechanisms.Morphological engineering of sensing materials at the nanometer and micrometer scales is crucial to obtaining superior sensor performance.This review focuses on the rapid development of morphological engineering technologies for flexible pressure sensors.We discuss different architectures and morphological designs of sensing materials to achieve high performance,including high sensitivity,broad working range,stable sensing,low hysteresis,high transparency,and directional or selective sensing.Additionally,the general fabrication techniques are summarized,including self-assembly,patterning,and auxiliary synthesis methods.Furthermore,we present the emerging applications of high-performing microengineered pressure sensors in healthcare,smart homes,digital sports,security monitoring,and machine learning-enabled computational sensing platform.Finally,the potential challenges and prospects for the future developments of pressure sensors are discussed comprehensively.

Tandem organic solar cells with efficiency over 19% via the careful subcell design and optimization

The series-connected tandem device strategy is an effective approach to promote the efficiency of organic solar cells(OSCs) with broadened absorption range and alleviated thermalization and transmission loss.In this article,two nonfullerene acceptors,FB rThCl and BTP-4Se,with complementary absorptions covering the range from 300 to 1,000 nm were designed and synthesized for the front and rear cell,respectively.The front cell based on D18:FBr-ThCl exhibited a Voc of 1.053 V with high external quantum efficiency(EQE) response values ranging from 300 to 740 nm.The rear cell with a ternary active layer PM6:BTP-4 Se:F-2F was optimized and afforded the Voc of 0.840 V and Jsc of 26.88 mA cm^(-2).Subsequently,the tandem device was constructed with a fully solution-processed interconnected layer of ZnO/PEDOT:PS S/PMA,and demonstrated a power conversion efficiency(PCE) of 19.55% with a Voc of 1.880 V,a Jsc of 13.25 mA cm^(-2) and an FF of 78.47%.

Structural optimization of acceptor molecules guided by a semi-empirical model for organic solar cells with efficiency over 15%

Despite much progress in organic solar cells(OSCs),higher efficiency is still the most desirable goal and can indeed be obtained through rational design of active layer materials and device optimization according to the theoretical prediction.Herein,under the guidance of a semi-empirical model,two new non-fullerene small molecule acceptors(NFSMAs)with an acceptor-donor-acceptor(A-D-A)architecture,namely,6 T-OFIC and 5 T-OFIC,have been designed and synthesized.6 T-OFIC exhibits wider absorption spectrum and a red-shifted absorption onset(λ_(onset))of 946 nm due to its extended conjugation central unit.In contrast,5 T-OFIC with five-thiophene-fused backbone has an absorption with theλ_(onset)of 927 nm,which is closer to the predicted absorption range for the best single junction cells based on the semiempirical model.Consequently,the device based on 5 T-OFIC yields a higher power conversion efficiency(PCE)of 13.43%compared with 12.35%of the 6 T-OFIC-based device.Furthermore,an impressive PCE of 15.45%was achieved for the5 T-OFIC-based device when using F-2 Cl as the third component.5 T-OFIC offers one of a few acceptor cases with efficiencies over 15%other than Y6 derivatives.

Improving current and mitigating energy loss in ternary organic photovoltaics enabled by two well-compatible small molecule acceptors

Ternary organic photovoltaic(OPV)strategy is an effective but facile approach to enhance the photovoltaic performance for single-junction devices.Herein,a series of ternary OPVs were fabricated by employing a wide bandgap donor(PBDB-TF)and two acceptor-donor-acceptor(A-D-A)-type nonfullerene small molecule acceptors(NF-SMAs,called F-2 Cl and 3 TT-OCIC).As the third component,the near-infrared SMA,3 TT-OCIC,has complementary absorption spectrum,narrow bandgap and wellcompatible crystallization property to the host acceptor(F-2 Cl)for efficient ternary OPVs.With these,the optimal ternary devices yield significantly enhanced power conversion efficiency of 15.23%,one of the very few examples with PCE higher than15%other than Y6 systems.This is mainly attributed to the increased short-circuit current density of 24.92 m A cm^(-2) and dramatically decreased energy loss of 0.53 e V.This work presents a successful example for simultaneously improving current,minimizing energy loss and together with modifying the morphology of active layers in OPVs,which will contribute to the further construction of high performance ternary OPVs.