| Organic Solar Cells(OSCs) is a kind of non-polluting and renewable energy sources, it is very significant to provide electricity and use solar energy in large scale. But actually, the application of OSCs is severely restricted due to the low photoelectric conversion efficiency. In OSCs, A large number of studies have shown that Implantating noble metal nanograting which helps to improve the light absorption of active layer, and the scale of grating is about several hundred nanometers. This is one of the effective techniques to improve the photoelectric conversion efficiency of OSCs. But there are few studies on metal grating with period less than100nm. In this paper, we introduce the silver nanograting with ultra-small period (20nm) to OSCs with P3HT:PCBM system, we studied theoretically the effect of the grating on OSCs’ absorption properties. In addition, some studies have also pointed out, there are the composite loses of carrier and the quenching of exciton at the surface of metal when the metal in direct contact with the polymer. Although metal nanograting is beneficial to improve light absorption of OSCs but which is not for the photoelectric conversion efficiency. The main conclusions are as follows: 1. First, in P3HT:PCBM system structure, the paper studied the absorption properties of the active layer for the silver nano-grating structure with ultra-small period. The results as follows:(1) The varing geometric parameters of the silver nanograting will mainly affect hot spot’s generation and intensity, and the change of width will be more significant than height effecting the light absorption of the active layer(2) Specifically, when h=30nm, the integrated absorption efficiency at the hybrid mode can reach47.90%, increased by36.50%than the equivalent plane structure. Thus a strong absorption was achieved with only24.5nm ultrathin equivalent active layer. Especially in the TM mode, the integrated efficiency of the absorption increased by102%. Furthermore, the more advantages are enhancement of broad absorption spectrum andangle-insensitive. When h=8nm, the strong electric effect of hot spot is weakened significantly because of reducing the height of the nanograting, while the improvement of the light absorption mainly due to increasing the effective thickness of the active layer.2. On considering of above study, the paper do a coating on silver nanograting with dielectric material, proposing the coating style which is an core-shell silver nanograting structure, to avoid exciton quenching at metallic silver/polymer interface. The results as follows:(1) For the core shell structure with no loss dielectric as the coating material, the results as following: The coating material does not affect the excitation of hot spot excited between the silver nanogratings, the integrated absorption efficiency will be improved, mainly owing to the inhibiting effect on absorption of the active layer will be weak, and the greater the refractive index of the dielectric coating materials, weaker inhibition. But the hot spot effect is the dominant role in enhancing absorption of cell.(2) For the core-shell structure with ZnO and TiO2as the specific coating materials, the following results:When h=30nm, in ZnO-Ag core-shell structure, the integrated absorption efficiency of active layer of Hybrid mode is up to43.63%, increased by57.68%with respect to the20.5nm equivalent thickness in the planar structure. In contrast, the absorption properties of TiO2-Ag core-shell structure are similar to that of the ZnO-Ag case, there is only0.29%difference on integrated absorption efficiency at the hybrid mode in the two cases, and they are all showed wide-angle absorption characteristic. When h=8nm, for TiO2-Ag and ZnO-Ag core-shell structures, the improvement of absorption are all not obvious。... |
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