Study of NIR long afterglow luminescent materials are used in silicon solar cells to produce electricity under dark condition

It is well known that the silicon solar cells can realize effective photoelectric conversion only under sunlight irradiation, and that can not generate electricity under dark condition. Thus, the effective working (photoelectric conversion) time of silicon solar cells throughout the whole day is very limited. In this paper, the up-conversion NIR long afterglow luminescent materials, Zn3Ga2-x-y-zGe2O10:xCr3+,yYb3+,zEr3+, were successfully prepared through high temperature calcination method. The structure, morphology, elemental composition and optical property of the prepared samples were analyzed by a series of characterization methods. In addition, the mechanisms of afterglow luminescent of these materials and the energy transfer mechanisms of up-conversion luminescent between the luminescent center Cr3+ and sensitizer ions (Yb3+ and Er3+) are discussed, respectively. Finally, the prepared luminescent materials are fixed on glass sheets with reflective capacity, and then are integrated with silicon solar cells in the form of a cover plate. And then, under dark conditions, the current density-voltage (J-V) curves and current density-time (J-T) curves of these silicon solar cells were tested to explore the influences of doping proportions of Cr3+, Yb3+, Er3+, Yb3+-Er3+ pairs and the calcination temperatures of Zn3Ga2-xGe2O10:xCr3+ on the power generation of the silicon solar cells. The results show that the photovoltaic conversion instantaneous efficiency of silicon solar cell with Zn3Ga1.975Ge2O10:1.0Cr3+,1.0 Yb3+,0.5Er3+ reaches the maximum value of 2.549 % under dark condition. The average efficiency within 300 s is 0.238%. At the same time, the silicon solar cell can generate dark current for up to 8.0 h, whose maximum dark current density and open-circuit voltage of 4.88 μA/cm2 and 0.914 mV, respectively. It is hoped that this study can provide some new ideas for silicon solar cells to generate electricity without sunlight irradiation.