Pyro-phototronic nanogenerator based on flexible 2D ZnO/graphene heterojunction and its application in self-powered near infrared photodetector and active analog frequency modulation

Pyro-Phototronic Effect for Advanced Photodetectors and Novel Light Energy Harvesting

Pyroelectricity was discovered long ago and utilized to convert thermal energy that is tiny and usually wasted in daily life into useful electrical energy. The combination of pyroelectricity and optoelectronic yields a novel research field named as Pyro-Phototronic, where light-induced temperature variation of the pyroelectric material produces pyroelectric polarization charges at the interfaces of semiconductor optoelectronic devices, capable of modulating the device performances. In recent years, the pyro-phototronic effect has been vastly adopted and presents huge potential applications in functional optoelectronic devices. Here, we first introduce the basic concept and working mechanism of the pyro-phototronic effect and next summarize the recent progress of the pyro-phototronic effect in advanced photodetectors and light energy harvesting based on diverse materials with different dimensions. The coupling between the pyro-phototronic effect and the piezo-phototronic effect has also been reviewed. This review provides a comprehensive and conceptual summary of the pyro-phototronic effect and perspectives for pyro-phototronic-effect-based potential applications.

Great Enhancement Effect of 20-40 nm Ag NPs on Solar-Blind UV Response of the Mixed-Phase MgZnO Detector

High-performance solar-blind UV detector with high response and fast speed is needed in multiple types of areas, which is hard to achieve in one device with a simple structure and device fabrication process. Here, the effects of Ag nanoparticles (NPs) with different sizes on UV response characteristics of the device are studied, the Ag NPs with different sizes that are made from a simple vacuum anneal method. Ag NPs with different sizes could modulate the peak response position of the mixed-phase MgZnO detector from near UV range (350 nm) to deep UV range (235 nm), and the enhancement effect of the Ag NPs on the UV response differs much with the crystal structure and the basic UV response of the MgZnO thin film. When high density 20-40 nm Ag NPs is induced, the deep UV (235 nm) response of the mixed-phase MgZnO detector is increased by 226 times, the I _uv/I _dark ratio of the modified device is increased by 17.5 times. The slight enhancement in UV light intensity from 20 to 40 nm Ag NPs induces multiple tunnel breakdown phenomena within the mixed-phase MgZnO thin film, which is the main reason for the abnormal great enhancement effect on deep UV response of the device, so the recovery speed of the modified device is not influenced. Therefore, Ag NPs with different sizes could effectively modulate the UV response peak position of mixed-phase MgZnO thin films, and the introduction of Ag NPs with high density and small size is a simple way to greatly increase the sensitivity of the mixed-phase MgZnO detector at deep UV light without decreasing the device speed.

An Fe-doped ZnO/BiVO4 heterostructure-based large area, flexible, high-performance broadband photodetector with an ultrahigh quantum yield

Pristine ZnO has been widely explored for its use in UV photodetectors; however, the utility of ZnO in broadband photodetectors is still a challenge as it absorbs in the UV region only with low quantum efficiency and responsivity that can be accredited to the high recombination rate of photo-generated charge carriers. To address this issue, we report an Fe-doped 2D ZnO thin film, obtained through band gap engineering, and a 1D electrospun mixed-inorganic monoclinic BiVO₄ nanofiber heterostructure on an ITO-coated PET substrate-based broadband photodetector (PD) with ultra-high responsivity and EQE values in comparison to PDs fabricated using expensive cleanroom techniques. BiVO₄ plays the dual role of absorbing photons in the visible and NIR regions and creating local electric fields at the interface of the Fe-doped ZnO (FZO)-BiVO₄ heterostructure, which helps in the separation of electron-hole pairs. The robustness of the flexible PD was further examined under the conditions of repeated bending cycles (up to 500), yielding a stable response. The responsivity values obtained for UV, visible and NIR irradiation are 7.35 A W^-1, 3.8 A W^-1 and 0.18 A W^-1 with very high EQE values of 2501.7%, 851.2% and 28.3%, respectively. The facile and cost-effective fabrication of the device with high performance provides a new approach for developing flexible electronics and high-performance optoelectronic devices.