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MoS2 has attracted extensive attention as the basic configuration of optoelectronic systems because of its outstanding optical and electronic properties. Although high performance MoS2-based photodetectors have been realized by many groups, these studies are still in their initial stages of research, and more importantly, the usual photocurrent or photovoltage signals are fundamentally susceptible, thus seeking novel structures or working principle devices becomes more fascinating. Here, the MoS2/Si heterojunction is prepared with a vertically standing nanoplate structure and we exploit it as a photovoltage, photocurrent and photoresistance-based multifunctional self-powered position sensitive detector (PSD). The PSD exhibits unprecedented performance with very high sensitivity (391.1 mV mm−1, 285.2 μA mm−1, and 21.61 KΩ mm−1 for photovoltage, photocurrent and photoresistance responses, respectively), excellent linearity (nonlinearity <2%), and a very fast response speed (4.75 ms/6.33 ms), all of which are much better than those obtained in many other systems. More importantly, it is the first time that lateral photoresistance (LPRE) is observed in a MoS2/Si heterojunction. Based on the theoretical analysis of the scattering or transportation modulation of photo-generated carriers on the drifted carriers in the MoS2/Si heterojunction, these results are well explained. [ABSTRACT FROM AUTHOR]

High temperature is a significant cause of failure of electromechanical products, achieving effective collection of triboelectric energy at high-temperatures is a major research emphasis. Improving the electrical outputs from triboelectric nanogenerator (TENG) in extreme environments is crucial for its large-scale application and remains challenging. Further considering the major potential application for TENG is wearable electronics, a series of SEBS/fatty acid (SEBS/FA) skin-like flexible films were fabricated, which exhibit adjustable surface triboelectricity and enhanced triboelectric outputs at high-temperatures. The SEBS/FA based TENGs possess remarkable durability of over 10,000 contact-separation cycles, and exhibit exceptional electrical outputs in the heat. Thereinto, the output efficiency of SEBS-OA (octanoic acid) is up to 302.32 % at 110 °C and still above 100 % at 150 °C. The SEBS/FA based TENGs can efficiently harvest the mechanical energy in high-temperature environments to power commercial capacitors and LEDs. Notably, the SEBS/FA films still show enhanced electrical outputs even under extreme conditions with working ambient temperatures up to 90 °C and significant deformation (λ ≤ 4). The excellent electromechanical performances enable SEBS/FA based TENGs to be served as flexible energy collector and self-powered touch sensor for motion capture. The real-time tactile trajectory can be accurately mapped by a 5 × 5 sensing array. The SEBS/FA films exhibit great potential in energy harvesting and active real-time tactile sensing system in extreme environments. [Display omitted] • SEBS/FA films with improved electrical output at high-temperatures were fabricated. • The V T /V Room of SEBS-OA at 110 °C is up to 302.32 %, and still higher than 100 % at 150 °C. • Specially, the V T /V Room of SEBS-ODA at 110 °C is as high as 797.93 %. • The V oc of SEBS/FA films donʼt decay after a long working cycle at 120 °C. • SEBS/FA films show enhanced electrical output even at 90 °C and significant deformation (λ ≤ 4). [ABSTRACT FROM AUTHOR]

Abstract: The recent discoveries of transition‐metal dichalcogenides (TMDs) as novel 2D electronic materials hold great promise to a rich variety of artificial van der Waals (vdWs) heterojunctions and superlattices. Moreover, most of the monolayer TMDs become intrinsically piezoelectric due to the lack of structural centrosymmetry, which offers them a new degree of freedom to interact with external mechanical stimuli. Here, fabrication of flexible vdWs p–n diode by vertically stacking monolayer n‐MoS2 and a few‐layer p‐WSe2 is achieved. Electrical measurement of the junction reveals excellent current rectification behavior with an ideality factor of 1.68 and photovoltaic response is realized. Performance modulation of the photodiode via piezo‐phototronic effect is also demonstrated. The optimized photoresponsivity increases by 86% when introducing a −0.62% compressive strain along MoS2 armchair direction, which originates from realigned energy‐band profile at MoS2/WSe2 interface under strain‐induced piezoelectric polarization charges. This new coupling mode among piezoelectricity, semiconducting, and optical properties in 2D materials provides a new route to strain‐tunable vdWs heterojunctions and may enable the development of novel ultrathin optoelectronics. [ABSTRACT FROM AUTHOR]

Abstract: The Cu(In,Ga)Se2 (CIGS) heterojunction, as a mature and high efficiency thin‐film solar cell, is rarely studied as a photodetector, especially in flexible substrates. In this paper, the structure of an ITO/ZnO/CdS/CIGS/Mo heterojunction is grown on the polyimide (PI) substrate to form a flexible CIGS heterojunction photodetector. The photodetector can work in a very wide band ranging from 350 to 1200 nm with responsivity up to 1.18 A W−1 (808 nm), detectivity up to 6.56 × 1010 Jones (cmHz1/2 W−1), and response time of 70 (/88) ms, respectively. Moreover, the piezophototronic effect is first used to investigate performance modulation of this device by effectively controlling the separation and transport of carriers at the interface of CdS/ZnO. Interestingly, by externally applying a 0.763% tensile strain, the photoresponsivity and detectivity of the photodetector exhibit a decrease from 1.18 to 0.88 A W−1, and from 6.56 × 1010 to 4.81 × 1010 Jones, respectively, while under a –0.749% externally static compressive strain, the photoresponsivity could be enhanced by ≈75.4% with a maximum of 2.07 A W−1, and the detectivity is improved by ≈66.1% with its peak value up to 10.9 × 1010 Jones. Meanwhile, the response time can be modulated from 99(/116) to 41.3(/42.6) ms. This work suggests that the CIGS heterojunction has great potential in novel applications for piezophototronic sensors and also gives a hint to modulate the performance of other multilayer heterostructures via the piezotronic effect. [ABSTRACT FROM AUTHOR]

Recently, vertically oriented few-layer 2D materials prepared by chemical vapor deposition (CVD) have attracted much attention due to their attractive properties. However, the integration of these materials as heterojunctions in optoelectronic sensors has been rarely reported. In this paper, large-area, high crystalline quality, and vertically oriented few-layered MoS2 (V-MoS2) nanosheets were synthesized and transferred successfully onto a silicon substrate to form a V-MoS2/Si heterojunction photodetector. The photodetector exhibits high photoelectric performances in a wide broadband ranging from visible to near-infrared with a photoresponsivity of up to 908.2 mA W−1, and a detectivity of up to 1.889 × 1013 Jones. More importantly, an unprecedented response speed of (rise time ∼ 56 ns, fall time ∼ 825 ns) was found in the photodetector by time response measurements, which is the best result achieved so far in any other 2D-based photodetectors or phototransistors. These excellent performances can be ascribed to the strong light absorption and the quick longitudinal intralayer carrier transport speed of the V-MoS2 nanosheets as well as the good heterojunction formed between V-MoS2 and Si. This intriguing vertical oriented structure in combination with both ultrafast time response and ultrahigh detectivity in the V-MoS2/Si heterojunction provide great potential for application in optoelectronic devices. [ABSTRACT FROM AUTHOR]

Abstract: A strain modulated solar‐blinded photodetector (PD) based on ZnO‐Ga2O3 core–shell heterojuction microwire is developed. This PD is highly sensitive to deep UV light centered at 261 nm. It performs ultrahigh sensitivity and spectral selectivity, which can response to rare weak deep UV light (≈1.3 µw cm−2) and almost no response to visible light wavelength ranges. Moreover, by using the piezo‐phototronic effect, the deep UV current response is enhanced to about three times under −0.042% static strain. This is a three way coupling effect among pizoelectric polarization, simiconductor properties, and optical excitation, which exists in noncentral symmetric wurtzite semiconductors such as ZnO, GaN, and CdS. By modulating the energy band diagrams and charge carriers in the junction area upon straining, the optoelectronic processes are regulated. The strain induced piezopotential modulates carrier transport in the heterostructure, which improves the response of the PD, with potential applications for health monitoring, smart systems, deep space exploration, and security communication. [ABSTRACT FROM AUTHOR]

Abstract: MoS2, as a typical transition metal dichalcogenide, has attracted great interest because of its distinctive electronic, optical, and catalytic properties. However, its advantages of strong light absorption and fast intralayer mobility cannot be well developed in the usual reported monolayer/few‐layer structures, which make the performances of MoS2‐based devices undesirable. Here, large‐area, high‐quality, and vertically oriented few‐layer MoS2 (V‐MoS2) nanosheets are prepared by chemical vapor deposition and successfully transferred onto an Si substrate to form the V‐MoS2/Si heterojunction. Because of the strong light absorption and the fast carrier transport speed of the V‐MoS2 nanosheets, as well as the strong built‐in electric field at the interface of V‐MoS2 and Si, lateral photovoltaic effect (LPE) measurements suggest that the V‐MoS2/Si heterojunction is a self‐powered, high‐performance position sensitive detector (PSD). The PSD demonstrates ultrahigh position sensitivity over a wide spectrum, ranging from 350 to 1100 nm, with position sensitivity up to 401.1 mV mm−1, and shows an ultrafast response speed of 16 ns with excellent stability and reproducibility. Moreover, considering the special carrier transport process in LPE, for the first time, the intralayer and the interlayer transport times in V‐MoS2 are obtained experimentally as 5 and 11 ns, respectively. [ABSTRACT FROM AUTHOR]