Enhanced Performance of a Self‐Powered Organic/Inorganic Photodetector by Pyro‐Phototronic and Piezo‐Phototronic Effects

Self‐powered photodetectors (PDs) have long been realized by utilizing photovoltaic effect and their performances can be effectively enhanced by introducing the piezo‐phototronic effect. Recently, a novel pyro‐phototronic effect is invented as an alternative approach for performance enhancement of self‐powered PDs. Here, a self‐powered organic/inorganic PD is demonstrated and the influences of externally applied strain on the pyro‐phototronic and the photovoltaic effects are thoroughly investigated. Under 325 nm 2.30 mW cm^‐2 UV illumination and at a ‐0.45% compressive strain, the PD's photocurrent is dramatically enhanced from ≈14.5 to ≈103 nA by combining the pyro‐phototronic and piezo‐phototronic effects together, showing a significant improvement of over 600%. Theoretical simulations have been carried out via the finite element method to propose the underlying working mechanism. Moreover, the pyro‐phototronic effect can be introduced by applying a ‐0.45% compressive strain to greatly enhance the PD's response to 442 nm illumination, including photocurrent, rise time, and fall time. This work provides in‐depth understandings about the pyro‐phototronic and the piezo‐phototronic effects on the performances of self‐powered PD to light sources with different wavelengths and indicates huge potential of these two effects in optoelectronic devices.     

Micrometer‐ and Nanometer‐Sized Organic Single‐Crystalline Transistors

The use of micrometer and nanometer‐sized organic single crystals to fabricate devices can retain all the advantages of single crystals, avoid the difficulties of growing large crystals, and provide a way to characterize organic semiconductors more efficiently. Moreover, the effective use of such “small” crystals will be beneficial to nanoelectronics. Here we review the recent progress of organic single‐crystalline transistors based on micro‐/nanometer‐sized structures, namely fabrication methods and related technical issues, device properties, and current challenges.     

Quasi‐Amorphous Inorganic Thin Films: Non‐Crystalline Polar Phases

Quasi‐amorphous thin films of BaTiO₃, SrTiO₃, and BaZrO₃ are the only known examples of inorganic, non‐crystalline, polar materials. The conditions under which they are formed and the origin of their polarity set these materials apart from other classes of inorganic materials. The most important feature of the quasi‐amorphous phase is that the polarity is the result of the orientational ordering of local bonding units but without any detectable spatial periodicity. This mechanism is reminiscent of that observed in ferroelectric polymers and permits compounds that do not have polar crystalline polymorphs, such as SrTiO₃ and BaZrO₃, to form polar non‐crystalline solids. In the present report, we provide an overview of the essential features of these materials including preparation, structure, and chemical composition. The report also reviews our current level of understanding and offers some guidelines for further development and application of non‐crystalline inorganic polar materials.     

Conjuncted Pyro‐Piezoelectric Effect for Self‐Powered Simultaneous Temperature and Pressure Sensing

Ferroelectric materials use both the pyroelectric effect and piezoelectric effect for energy conversion. A ferroelectric BaTiO₃‐based pyro‐piezoelectric sensor system is demonstrated to detect temperature and pressure simultaneously. The voltage signal of the device is found to enhance with increasing temperature difference with a sensitivity of about 0.048 V °C^?1 and with applied pressure with a sensitivity of about 0.044 V kPa^?1. Moreover, no interference appears in the output voltage signals when piezoelectricity and pyroelectricity are conjuncted in the device. A novel 4 × 4 array sensor system is developed to sense real‐time temperature and pressure variations induced by a finger. This system has potential applications in machine intelligence and man–machine interaction.     

High‐Throughput Near‐Field Optical Nanoprocessing of Solution‐Deposited Nanoparticles

The application of nanoscale electrical and biological devices will benefit from the development of nanomanufacturing technologies that are high‐throughput, low‐cost, and flexible. Utilizing nanomaterials as building blocks and organizing them in a rational way constitutes an attractive approach towards this goal and has been pursued for the past few years. The optical near‐field nanoprocessing of nanoparticles for high‐throughput nanomanufacturing is reported. The method utilizes fluidically assembled microspheres as a near‐field optical confinement structure array for laser‐assisted nanosintering and nanoablation of nanoparticles. By taking advantage of the low processing temperature and reduced thermal diffusion in the nanoparticle film, a minimum feature size down to ≈100 nm is realized. In addition, smaller features (50 nm) are obtained by furnace annealing of laser‐sintered nanodots at 400 °C. The electrical conductivity of sintered nanolines is also studied. Using nanoline electrodes separated by a submicrometer gap, organic field‐effect transistors are subsequently fabricated with oxygen‐stable semiconducting polymer.     

Carbon Nanotube Field‐Effect‐Transistor‐Based Biosensors

There is an explosive interest in 1D nanostructured materials for biological sensors. Among these nanometer‐scale materials, single‐walled carbon nanotubes (SWNTs) offer the advantages of possible biocompatibility, size compatibility, and sensitivity towards minute electrical perturbations. In particular, because of these inherent qualities, changes in SWNT conductivity have been explored in order to study the interaction of biomolecules with SWNTs. This Review discusses these interactions, with a focus on carbon nanotube field‐effect transistors (NTFETs). Recent examples of applications of NTFET devices for detection of proteins, antibody–antigen assays, DNA hybridization, and enzymatic reactions involving glucose are summarized. Examples of complementary techniques, such as microscopy and spectroscopy, are covered as well.