| Dye-sensitized solar cells (DSSCs) have attracted extensive interest due to its high-efficiency, easy, low-cost, and environment-friendly preparation process. However, it is a challenge to further increase the efficiency of DSSCs due to the nature drawbacks of TiO2nanoporous electrode, such as numerous grain boundaries existing in the nanoparticle film and the slower electron mobility of TiO2as compared with other materials. To solve these problems, we optimized the photoanodes of DSSCs using electrospraying and electrospinning technique, which were summerized as following:1. Nanocrystalline TiO2electrodes are fabricated using commercially available powers (P25) by electrospray coating technique. The structures and morphologies of the film, which ultimately influence the solar cell performances, can be controlled via changing the spraying distance. The optimized spraying distance for the maximum short-circuit photocurrent density (Jsc) of the cells is6cm, and thus a great improvement of the power conversion efficiency (PCE). The improvement of Jsc can be mainly ascribed to the enhanced light scattering and better ion-diffusion path, which is caused by presence of the secondary spheres produced in electrospraying process.2. We first fabricate a highly transparent nanocrystalline TiO2films by electrospinning technique. It is based on a transmutation process from as-spun nanofibers with an appropriate amount of tri-ethanolamine added to the precursor. By photoluminescence (PL) spectroscopy analysis, it is found that these films possess rich bulk oxygen vacancies (BOVs, PL band at621-640nm). Contrastively, the dominant peak in PL spectrum of the spin-coated film prepared from the same precursor solution is the emission from surface oxygen vacancies (SOVs, PL band at537-555nm). The rich BOVs in electrospun TiO2films induces large open-circuit voltage (Voc) and fill factor (FF) improvements in DSSCs, and thus a large improvement of PCE. Detection of ultraviolet (UV) light is usually based on the photoconductivity effect of semiconductors. However, this type of photodetectors possess a long recovery time of>1s due to the absorption and dis-absorption of oxygen at the nanomaterial surface without and with light irradiation, limiting its application. Herein, on the basis of DSSCs, we demonstrate the application of a photoelectrochemical cell (PECC) with an unsensitized semiconductor film as work electrode as a fast, high responsivity, and stable self-powered UV-photodetector for detecting the UV light.1. In details, we assembled unsensitized TiO2NC electrode, electrolyte containing I-/I3-redox and Pt counter electrode into a sandwiched PECC. By connecting a PECC to an ammeter, the intensity of UV light have been quantified using the output Jsc signal without a power source. This self-powered UV-photodetector exhibits a high on/off ratio of2698, a rise time of0.08s and a decay time of0.03s for Jsc signal.2. The nature drawbacks of the conventional TiO2NC films are numerous grain boundaries existing in the nanoparticle film and the slower electron mobility of TiO2as compared with other materials. To solve these problems, we design and fabricate a TiO2/SnO2branched heterojunction nanostructure with TiO2branches on electrospun SnO2nanofibers (B-SnO2NF) networks, which serves as a model architecture for efficient self-powered UV-photodetectors based on PECC. The nanostructure simultaneously offers a low degree of charge recombination and a direct pathway for electron transport. Without correcting64.5%loss of incident photons resulting from light absorption and scattering by the FTO glass, the PCE reaches14.7%at330nm, more than twice as large as the TiO2NC-film based PECC (6.4%). Under UV irradiation, the self-powered UV-photodetector exhibits a high responsivity of0.6A/W, a high on/off ratio of4550, a rise time of0.03s and a decay time of0.01s for Jsc signal. |
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