High-performance ReS2 photodetectors enhanced by a ferroelectric field and strain field

Flexible optoelectronic devices have numerous applications in personal wearable devices, bionic detectors, and other systems. There is an urgent need for functional materials with appealing electrical and optoelectronic properties, stretchable electrodes with outstanding mechanical flexibility, and gate medium with flexibility and low power consumption. Two-dimensional transition metal dichalcogenides (TMDCs), a novel kind of widely studied optoelectrical material, have good flexibility for their ultrathin nature. P(VDF-TrFE) is a kind of organic material with good flexibility which has been proved to be a well-performing ferroelectric gate material for photodetectors. Herein, we directly fabricated a well-performing photodetector based on ReS₂ and P(VDF-TrFE) on a flexible substrate. The device achieved a high responsivity of 11.3 A W⁻¹ and a high detectivity of 1.7 × 10¹⁰ Jones from visible to near-infrared. Moreover, with strain modulation, the device's responsivity improved 2.6 times, while the detectivity improved 1.8 times. This research provides a prospect of flexible photodetectors in the near-infrared wavelength.

The flexible ReS₂/P(VDF-TrFE) hybrid photodetector could be enhanced by a ferroelectric field and strain field.

The Influence Mechanism of Temperature and Storage Period on Polarization Properties of Poly (Vinylidene Fluoride-Trifluoroethylene) Ultrathin Films

The effect of testing temperature and storage period on the polarization fatigue properties of poly (vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) ultrathin film devices were investigated. The experimental results show that, even after stored in air for 150 days, the relative remanent polarization (Pr/Pr(0)) of P(VDF-TrFE) of ultrathin films can keep at a relatively high level of 0.80 at 25 °C and 0.70 at 60 °C. To account for this result, a hydrogen fluoride (HF) formation inhibition mechanism was proposed, which correlated the testing temperature and the storage period with the microstructure of P(VDF-TrFE) molecular chain. Moreover, a theoretical model was constructed to describe the polarization fatigue evolution of P(VDF-TrFE) samples.

Investigation of the mechanical properties and biocompatibility of planar and electrospun alkene-styrene copolymers against P(VDF-TrFE) and porcine skin: Potential use as second skin substrates

Elastomers have been used in a variety of biomedical fields, including tissue engineering, soft robotics, prostheses, and cosmetics. Elastomers used for skin grafting scaffolds tend to be biodegradable, but other applications require perdurable elastomers. Advances in perdurable elastomers would allow for the development of a range of substrates useful in the creation of joint prostheses, chronic neural electrodes, implantables, and wearables. Still, for these, tailored mechanical properties and biocompatibility are required. In this work, several perdurable alkene-styrene elastomers and novel polymer blends are investigated for their stress-strain curves; with quantification of Young's moduli, fatigue behavior and standard biocompatibility. In particular, this study attempts to study polymers with mechanical properties similar to the complex characteristics of skin, through comparison with porcine skin samples. Poly (vinylidene fluoride-trifluoroethylene), P(VDF-TrFE), a flexible polymer previously used as a wearable sensor and second skin component, was here used for comparison studies. Interestingly, this study points out that elastomer mechanical properties can be modulated to better replicate the elastic modulus of skin, in particular for KratonTM D1152, a Styrene-Butadiene-Styrene block copolymer. Namely, this is the case when such an elastomer is prepared as an electrospun matrix or as a flat dense film under low temperatures. Moreover, a specific method was optimized to obtain electrospun fibers of this alkene-styrene copolymer.

Flexible and Robust Piezoelectric Polymer Nanocomposites Based Energy Harvesters

Environment friendly, flexible, and robust sensors have attracted considerable research attention due to their potential for a wide range of devices in energy generation and harvesting, sensing, and biomedical applications. In this manuscript, we demonstrate a lead-free, solution processed flexible piezoelectric energy generator based on a nanocomposite film, consisting of MgO nanoparticles of sizes around <50 nm, embedded in poly(vinylidene difluoride) [PVDF] and its copolymer with trifluoroethylene, that is, P(VDF-TrFE) matrix. Piezoelectric, ferroelectric, and leakage current measurements made on samples with various concentrations of MgO nanoparticles revealed a dramatic improvement in these characteristics at 2 wt % MgO with nearly 50% increase in the piezoelectric coefficient as compared to pure P(VDF-TrFE), attributed to the preferred conformation of P(VDF-TrFE) chain, improved crystallinity of the P(VDF-TrFE) matrix, and uniform distribution of nanoparticles. Assessment of the interactions between -OH groups attached to MgO surface and P(VDF-TrFE), carried out using Fourier-transform infrared spectroscopy (FTIR), suggested weak van der Waals forces between -OH groups and P(VDF-TrFE) being responsible for the observed improvement. This flexible nanocomposite device exhibits superior energy harvesting performance with over two-times improvement in the voltage output (2 V) compared to device using P(VDF-TrFE) films alone. Along with superior electrical properties, nanocomposites also exhibit excellent endurance against electrical as well as mechanical fatigue, with piezoelectric coefficient remaining unchanged even after 10 000 bending cycles, supporting their suitability in flexible energy harvesting applications.

An efficient route to fabricate fatigue-free P(VDF-TrFE) capacitors with enhanced piezoelectric and ferroelectric properties and excellent thermal stability for sensing and memory applications

P(VDF-TrFE), the best known ferroelectric polymer, suffers from a rather low piezoelectric response as well as poor electrical fatigue life, hampering its application potential.