Advances in Self-Powered Ultraviolet Photodetectors Based on P-N Heterojunction Low-Dimensional Nanostructures

Self-powered ultraviolet (UV) photodetectors have attracted considerable attention in recent years because of their vast applications in the military and civil fields. Among them, self-powered UV photodetectors based on p-n heterojunction low-dimensional nanostructures are a very attractive research field due to combining the advantages of low-dimensional semiconductor nanostructures (such as large specific surface area, excellent carrier transmission channel, and larger photoconductive gain) with the feature of working independently without an external power source. In this review, a selection of recent developments focused on improving the performance of self-powered UV photodetectors based on p-n heterojunction low-dimensional nanostructures from different aspects are summarized. It is expected that more novel, dexterous, and intelligent photodetectors will be developed as soon as possible on the basis of these works.

Constructing a Green Light Photodetector on Inorganic/Organic Semiconductor Homogeneous Hybrid Nanowire Arrays with Remarkably Enhanced Photoelectric Response

We demonstrate that a novel photodetector is constructed by CdS/poly( p-phenylene vinylene) (PPV) homogeneous hybrid nanowire arrays via a simple template-assisted electrochemical codeposition approach. Owing to the well-matched energy levels between CdS and PPV, the recombination of photogenerated electrons and holes in CdS/PPV hybrid nanowire arrays is greatly inhibited. It is found that the homogeneous hybrid nanowire arrays exhibit remarkably enhanced photoelectric response and the ON/OFF ratio by 17 times compared to the individual CdS component. More importantly, the CdS/PPV hybrid nanowire arrays are observed with significant spectral selectivity especially for green light under 545 nm. In addition, a straight linear relationship is obtained between the ON/OFF ratios and the illumination intensities, implying that the quantitative detection of illumination intensity can be achieved. The new as-prepared homogeneous hybrid organic/inorganic semiconductor nanowire arrays have a bright prospect for applications in high-sensitivity and high-speed green photodetectors.

Controlling the Interface Areas of Organic/Inorganic Semiconductor Heterojunction Nanowires for High-Performance Diodes

A new method of in situ electrically induced self-assembly technology combined with electrochemical deposition has been developed for the controllable preparation of organic/inorganic core/shell semiconductor heterojunction nanowire arrays. The size of the interface of the heterojunction nanowire can be tuned by the growing parameter. The heterojunction nanowires of graphdiyne/CuS with core/shell structure showed the strong dependence of rectification ratio and perfect diode performance on the size of the interface. It will be a new way for controlling the structures and properties of one-dimensional heterojunction nanomaterials.

Active methylenes in the synthesis of a pyrrole motif: an imperative structural unit of pharmaceuticals, natural products and optoelectronic materials

Pyrrole is one of the most important azaheterocycles, due to its wide range of applications in pharmaceuticals and optoelectronic materials, coupled with its utility as an intermediate in natural products.

Cross-stacked single-crystal organic nanowire p-n nanojunction arrays by nanotransfer printing

We fabricated cross-stacked organic p-n nanojunction arrays made of single-crystal 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS-PEN) and fullerene (C60) nanowires as p-type and n-type semiconductors, respectively, by using a nanotransfer printing technique. Single-crystal C60 nanowires were synthesized inside nanoscale channels of a mold and directly transferred onto a desired position of a flexible substrate by a lubricant liquid layer. In the consecutive printing process, single-crystal TIPS-PEN nanowires were grown in the same way and then perpendicularly aligned and placed onto the C60 nanowire arrays, resulting in a cross-stacked single-crystal organic p-n nanojunction array. The cross-stacked single-crystal TIPS-PEN/C60 nanowire p-n nanojunction devices show rectifying behavior with on/off ratio of ∼ 13 as well as photodiode characteristic with photogain of ∼ 2 under a light intensity of 12.2 mW/cm(2). Our study provides a facile, solution-processed approach to fabricate a large-area array of organic crystal nanojunction devices in a desired arrangement for future nanoscale electronics.

Growth of axial nested P–N heterojunction nanowires for high performance diodes

The axial nested P–N heterojunction nanowires have proved to be better microelectronic devices because of their bigger area of junction.

Inorganic-organic p-n heterojunction nanotree arrays for a high-sensitivity diode humidity sensor

Large-area and ordered arrays (16 cm(2)) of an inorganic-organic p-n heterojunction nanotree (NT) were successfully fabricated. The nanotree arrays consist of ZnO nanorods (NRs) as backbones and CuTCNQ (TCNQ = 7,7,8,8-tetracyanoquinodimethane) NRs as branches. The sizes of CuTCNQ NRs can be tuned by the thickness of the Cu layer deposited on the surface of ZnO NR. The CuTCNQ/ZnO NT arrays displayed excellent diode nature and obvious size-dependent rectification ratios were observed. Moreover, the CuTCNQ/ZnO NT arrays were first applied for the fabrication of a diode-type humidity sensor, which displayed ultrahigh sensitivity and quick response/recovery properties at room temperature. The detection limitation of this new diode-type humidity sensor lowers to 5% relative humidity (RH).

Synthesis of (4-hexyloxybenzoyl)butylsaure methyl amide/poly(3-hexylthiophene) heterojunction nanowire arrays

Large-area P-N heterojunction organic semiconductor nanowire combined (4-hexyloxybenzoyl)butylsaure methyl amide (H-t-B) and Poly (3-hexylthiophene) (P3HT) were fabricated and the morphology and photoelectric properties were investigated by the growth of composition. The performance of light on/off switching of the H-t-B/P3HT heterojunction nanowire arrays was measured by the light irradiation on and off, the current in the devices showed two distinct states, the current was only 0.34 μA in the dark, while the current can reach 1.37 μA under the illumination of 45 mW/cm(2). The on/off switching ratio for the device of the heterojunction nanowire arrays is about 4.03.

p-n Heterojunction on ordered ZnO nanowires/polyaniline microrods double array

Recently, there has been growing interest in the design of novel nano- and/or microscaled heterojunctions consisting of two distinctive ordered semiconductor arrays for highly efficient p-n diodes used in optical, optielectronic, and microelectronic devices. Here, we report the attainment of an ordered double array comprising of p-type polyaniline microrods and n-type ZnO nanowires by a controlled electrochemical deposition method. Extensive chemical and physical characterizations have been performed on the fabricated p-n heterojunction. The double-array p-n heterojunction exhibits good rectifying characteristics, the rectification ratio of which exhibits a minimum at an illumination density of 93 mW cm(-2), making it suitable for high-sensitivity photodetectors. This research is expected to open up a new avenue for the development of highly efficient and sensitive p-n heterojunction diodes and possibly serve as the building blocks for future nanoelectronics.