heterojunctions have been constructed and demonstrated for controlling optical, [1] electrical, [2] mechanical [3] and magnetic characteristics. [4] In particular, semiconductor heterojunctions as the core of light-emitting diodes (LEDs) have played vital roles in electric-driven lighting and display devices. The electric potential of a semiconductor heterojunction has a strong positive effect on charge carrier transport at the interface and can tune/ control the behaviors of light emitting. [5] The advances in lighting technology have greatly promoted the development of artificial intelligence, biotechnology and flexible optoelectronics. [6] At present, almost all LEDs are driven by external power supply through wire connecting electrodes. However, the high-efficiency heterojunction material driven by Newton force to achieve the stress light-emitting devices is still limited in the present research. Thus, the exploration of such a new type of light-emitting device without wires and electrodes not only supplies advanced heterojunction systems for light-emitting but also provides a prospective reference for the future multiapproach energy conversion with extended applications.As a special type of light source, mechanoluminescence (ML) materials are capable of generating photon emissions in response to mechanical stimuli. In comparison with LEDs based on electroluminescence (EL), ML provides sustainable light output by excitation of mechanical energy ubiquitously available in nature. During the past decade, ML materials have attracted widespread interests due to their promising applications in stress sensing, display, artificial skin, bioimaging, anti-counterfeiting, structure fatigue diagnosis, night surveillance and flexible optoelectronics. [7][8][9][10] However, the recent developments of highperformance ML materials are not as fast as other luminescence systems such as photoluminescence (PL)/EL, which is attributed to the lack of rational design of ML material systems guided by the in-depth theoretical exploration in the mechanism. ML materials known to date are typically homogenous structures, which offer limited space for optimizing the ML performance. Therefore, further improving the ML performance by exploiting heterostructures remains a challenge for present research. [11,12] In this work, we fabricate a class of ZnS/CaZnOS heterostructures, which flexibly tune the efficient and reproducible Actively collecting the mechanical energy by efficient conversion to other forms of energy such as light opens a new possibility of energy-saving, which is of pivotal significance for supplying potential solutions for the present energy crisis. Such energy conversion has shown promising applications in modern sensors, actuators, and energy harvesting. However, the implementation of such technologies is being hindered because most luminescent materials show weak and non-recoverable emissions under mechanical excitation. Herein, a new class of heterojunctioned ZnS/CaZnOS piezophotonic systems is presented, which disp...

Recently, trivalent chromium ion doped phosphors have exhibited significant application potential in broadband near-infrared (NIR) phosphor-converted light-emitting diodes (pc-LEDs). However, developing an NIR phosphor with both broad emission bandwidth and excellent luminescence thermal stability is still a great challenge. Here, we demonstrate an NIR phosphor, ScF3:Cr3+, which can fulfill both conditions simultaneously. The prepared phosphors show broadband emission in the range of 700 to 1100 nm, with a full width at half-maximum (FWHM) of 140 nm peaking at 853 nm. These phosphors also demonstrate an excellent luminescence thermal stability (the emission intensity of ScF3:Cr3+ keeps 85.5% at 150 °C compared with the value at room temperature). An NIR pc-LED based on blue LED chips was fabricated and tested. The results show that the NIR pc-LED can yield strong broadband NIR emission. This work not only provides a promising phosphor for the application of NIR pc-LEDs but also has important guiding significance for effect of synthesis conditions on the luminescence properties of Cr3+-doped fluorides.

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Metrics & MoreArticle Recommendations CONSPECTUS: Mechanoluminescence is a process of light emission from materials in response to external mechanical actions. As mechanical energy is ubiquitously available in nature, mechanoluminescence can provide sustainable solutions to challenging problems in the fields of biology and optoelectronics as well as energy and environmental sciences. In particular, remote delivery of light through mechanoluminescence can also be achieved by noncontact forces from ultrasonic waves and magnetic fields, which enables noninvasive diagnosis and therapy in biomedical applications. Owing to the well-recognized merits, the research of mechanoluminescence has evolved into a highly interdisciplinary field, which in turn has inspired considerable interest in the development of novel mechanoluminescence materials and devices for boosting the emission performances such as brightness, repeatability, and spectral tunability. Mechanoluminescence was originally observed in processes associated with fracture and plastic deformation of materials, which are characterized by inefficient and nonreproducible light emissions. Therefore, current research is mainly directed to repeatable mechanoluminescence through elastic deformation for the continuous generation of light. Such elastico-mechanoluminescence is primarily observed in host materials with piezoelectricity and doped with activator ions such as manganese and lanthanide. Upon the application of mechanical stress, the piezoelectric hosts establish internal electric fields that trigger electronic transitions between the dopant-associated energy levels, eventually giving rise to light emissions from the dopant ions. On the basis of the learned knowledge, various host/dopant combinations have been synthesized and tested for mechanoluminescence in the past few years. Meanwhile, novel composite structures and devices incorporated with the mechanoluminescence materials have also been designed for an efficient light generation under different forms of mechanical actions, such as compressing, stretching, and rubbing. The significant progress in mechanoluminescence study has generated new opportunities for fundamental research and technological applications. To inspire and guide further investigations in this field, we systematically review emerging mechanoluminescence systems and their frontier applications. We focus on emerging host materials that have been identified to render bright mechanoluminescence with deliberately controlled emission characteristics, along with an analysis of the structure−property relationship in these materials. We also discuss innovative methodologies for translating mechanoluminescence into various cuttingedge device applications by precisely controlling the interaction of mechanoluminescence materials and their surrounding environments. We attempt to provide the rationale behind these developments, and simultaneously highlight future opportunities and challenges for mechanoluminescence.