Flexible Fiber-Shaped Solar Cells With The Near-Infrared Light Response:Design,Assembly And Photoelectrical Measurement

The flexible fiber-shaped solar cells (FSCs) have attracted much attention in the past few years due to their advantages such as weavability, lightweight, low cost, and extensive applications. However, the research about FSCs is still in the start-up stage in and out of the abroad. Many questions are remained to be resolve, for example, it can’t absorb near-infrared light and can not utilize the solar spectrum efficiently.Herein a flexible fiber-shaped solar cells with near-infrared light response is designed. By introducing up-conversion rare earth materials into the FSCs, it can not only enhance the absorption of the near-infrared light, but also open up the possibility of developing fiber-shaped electrical sources for wireless biological nanorobots and many other biodevices. The construction of FSC involves four steps as follow.Firstly, Yb3+, Er3+and tellurite glasses are used as the rare earth activated ion and substrate materials respectively. By using these materials, the glass fiber with up-conversion luminescence is made. As the substrate of FSCs, it has a good performance of flexibility and can be bent significantly. When the fiber is irradiated by the980nm laser, it has the visible green luminescence. The prepared up-conversion glass fiber is used as the substrate of FSCs with the near-infrared light response. Secondly, the conductive layer (ITO film) is prepared on the continuously rotating up-conversion glass fiber by the radio frequency magnetron sputtering system. The best sputtering parameters are determined by analyzing the influence of work pressure, sputtering power, oxygen partial pressure and sputtering time on the transmittance and resistivity of the film. The SEM image of the prepared ITO film shows that the film has a homogeneous thickness of300nm. The resistivity of the film is1.2×10-4Ωm.Thirdly, ZnO nanorods array film is orderly grown on the up-conversion conductive glass fiber by two-step method. As the seed layer, ZnO nanocrystal film is prepared by the magnetron sputtering equipment. Then, ZnO nanorods array is grown on the seed layer by the wet chemical solutions. The SEM images show that the growth of ZnO nanorods is restricted by the seed layer which has a big relationship with the preparation of well-aligned nanorods array. The influence of growth time is also studied. The glass fiber with the ZnO nanorods array is used as the anode of FSCs with the near-infrared light response.Finally, the prepared anode is sensitized by N719. By using platinum wire (d=0.025mm) as the counter electrode, the two electrodes are worn into the transparent capillary (d=lmm). The fiber-shaped photovoltaic cells with the near-infrared light response is assembled by injecting the electrolyte into the capillary.The assembled photovoltaic devices is tested by the standard solar simulator (AM1.5,100mW/cm2). The results show that the open circuit voltage (Voc) is343mV; the short circuit current density (Jsc) is0.01mA/cm2, the fill factor (FF) is28%. Under the irradiation of a980-nm laser with a power of1W, the device exhibits a maximal output power of0.007μ W.As a physical model, the assembled cell indicates the feasibility of fiber-shaped photovoltaic cells in the theory and show the broad prospect in the field of biological electrical sources. Considering the low photoelectric conversion efficiency, we can improve the preparation of substrate and each film, enhance the efficiency and other characteristics of the photovoltaic cells to satisfy the practical application value.