Photoelectric efficiency enhancement of a polycrystalline silicon solar cell coated with an EVA film containing Eu3+ complex by addition of modified SiO2

As an effective luminescent down-shifting (LDS) species, Eu3+ complexes have been doped in ethylene-vinyl acetate (EVA) films to improve the spectral response of silicon photovoltaic modules in the ultraviolet region. One key point about the improvement of photoelectric conversion efficiency by the LDS technique is increasing the fluorescence intensity of the EVA composite film as far as possible while staying within the visible light transmittance of the film. Around this point, we attempt to offer an idea for further studies. In this study, nano-SiO2 modified by a silane coupling agent was doped into EVA film with a fixed content of Eu3+ complex by the casting method. The experimental results show that when the modified SiO2 content is within 4%, the fluorescence of the EVA composite film gradually increases with increase in the modified SiO2 content and before formation of EVA composite film, the fluorescence intensities have no difference between the mixture with modified SiO2 and that without modified SiO2. SEM and AFM images of the EVA composite films show that the complex particles are probably enwrapped by aggregations of the modified SiO2 during the film-forming process, which strengthens the rigidity of the Eu3+ complex in the structure and results in the enhancement of fluorescence intensity. When the modified SiO2 content is within 2%, the visible light transmittance of the EVA film only slightly decreases. The photoelectric conversion efficiency of polycrystalline silicon solar cell coated with the composite film increases from 12.13% to 12.29%. Hence, the study provides a feasible approach to improve the LDS technique and has a potential application value.