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The adverse effect of ultraviolet (UV) radiation on human beings has sparked intense interest in the development of new sensors to effectively monitor UV and solar exposure. This paper describes a novel low-cost and flexible graphene oxide (GO)-based paper sensor capable of detecting the total amount of UV or sun energy delivered per unit area. GO is incorporated into the structure of standard printing paper, cellulose, via a low-cost fabrication technique. The effect of UV and solar radiation exposure on the GO paper-based sensor is investigated using a simple color change analysis. As a result, users can easily determine the amount of ultraviolet or solar energy received by the sensor using a simple color analysis application. A neural network (ANN) model is also explored to learn the relation between UV color intensity and exposure time, then digitally display the results. The accuracy for the developed ANN reached 96.83%. The disposable, cost-effective, simple, biodegradable, safe, and flexible characteristics of the paper-based UV sensor make it an attractive candidate for a variety of sensing applications. This work provides new vision toward developing highly efficient and fully disposable GO-based photosensors. [ABSTRACT FROM AUTHOR]

In this paper, we report the development of an oxygen sensor using a simple device made from a film of ZnO crystals dispersed over a paper surface. Due to the high porosity of this kind of device made from paper and ZnO, a large photoconductive effect is observed as result of the fast absorption and desorption of oxygen from the ZnO surface. To detect oxygen, we propose to use ultraviolet (UV) illumination over the photoconductive surface of the sensor, the applied UV light produces oxygen desorption causing current variations through the sensor that are proportional to the oxygen presence nearby the sensor surface. The sensor developed in this paper is attractive because it is remarkably easy to fabricate, employs only very low-cost materials for its construction, and shows a better sensitivity at low concentration of oxygen at partial vacuum environments. [ABSTRACT FROM PUBLISHER]

We proposed and experimentally demonstrated a cost-efficient and easy-to-fabricate flexible thin-film nanocrystal quantum dot (NCQD) photodetector, by sandwiching a piece of NCQD-soaked tracing paper between two PEDOT:PSS electrodes. The highly conductive and transparent multilayer polymer electrodes are printed with an office inkjet printer without further patterning on commercial unmodified transparency films. The tracing paper is able to act as both the bed for NCQD attachment and the interspacing layer to prevent short-circuiting in vertical devices. Consistent increase in device performance is observed when the bending radius becomes smaller. Linear I-V characteristics are obtained, which show our device structure works as a photoconductor. [ABSTRACT FROM PUBLISHER]

Recently, flexible intelligent wearable devices are in highly demand and it is urgent to increase the flexibility of traditional devices. Organometallic trihalide perovskite materials have become a hot spot in the photoelectric field due to its outstanding optoelectronic properties, which can be crystallized from solutions and vapors. Herein, we demonstrated a simple approach to flexible thin CH 3 NH 3 PbI 3 perovskite films on paper substrates using a dual-source physical vapor deposition method and a brush-coating method. The photodetector devices from the two methods have similar photodetecting and repeatable performances. They well maintained the optoelectronic functionality under bending conditions. Typically, up to 75% of its initial photocurrent was remained after 500 bending cycles, demonstrating good stability against bending deformation. Additionally, a 6 × 6 perovskite photodetector array based on stretchable origami-based techniques were fabricated. It has excellent all-optical acquisition capability and provides potential application in three-dimensional photo sensing. [Display omitted] • Thin perovskite films were deposited on paper substrates using both vapor and solution methods. • The paper-based photodetectors demonstrated good stability against bending deformation, even up to 500 bending cycles. • An origami-based perovskite photodetector array has excellent all-optical acquisition capability. [ABSTRACT FROM AUTHOR]

ZnO thin films were deposited on paper substrates by radio frequency magnetron sputtering at room temperature. By appropriate controlling the sputtering pressure, highly oriented (002) ZnO film with large grain size and low defect density can be obtained. Metal-semiconductor-metal structure ultraviolet photodetectors (UVPDs) were fabricated based on the ZnO/paper films and their optoelectronic response properties were investigated in detail. The optimum UVPD exhibits high UV sensitivity, showing peak responsivity at 380 nm. At applied voltage of 10 V, the UVPD has a high responsivity of 0.86 A/W and a high on/off ratio of ~600. Moreover, the flexible UVPD exhibits excellent stability and reproducibility under different bending conditions. The high flexibility of the UVPD was attributed to the compact and continuous properties of the sputtered film. The excellent operating characteristics make the UVPD a potential candidate for wearable UV meters and communication devices. • Paper based ultraviolet photodetector exhibits high flexibility and stability. • The paper substrate is renewable, biodegradable and abundant. • ZnO film was grown on paper at room temperature by magnetron sputtering. • Highly oriented (002) ZnO film was prepared with appropriate sputtering pressure. [ABSTRACT FROM AUTHOR]