抄録
The temperature rise of solar cells is one of the factors to decrease conversion efficiency of photovoltaic. We have developed a wavelength selective transmission thin film to prevent from temperature rise by cut-off near infrared rays which cause temperature rise. However, these optical thin films were designed with considering only normal incidence of sunlight. The change of incident angle of solar light shifts cut-off band to the short wavelength, which is required to power generation. Furthermore, these films had ripples in transmittance of visible light, and it caused little decrease of conversion efficiency. Therefore, in this research, we designed and prepared new wavelength selective transmission thin film with considering incident angular dependence of transmittance and the prevention of visible area ripples. Characteristics of former optical film and newly designed one were compared. Both of films were able to prevent from temperature rise of the solar cells than ordinary cover glass. However, former thin film could not prevent from decrease of conversion efficiency. On the other hand, conversion efficiency with newly designed thin film was higher than ordinary cover glass. According to these results, it was clarified that the shift of cut-off band by the incident angle change and ripples of visible band transmittance are important factor of the decrease of conversion efficiency, and prevention of them is important for actual use of photovoltaic.
