1. Introduction
Characterization of materials is of importance for fabrication of any semiconductor device. Generally, the finished products are tested and characterized in order to improve and or maintain quality control [1]. Photovoltaic (PV) devices are usually designed on the basis of standard meteorological data. However, spectral variation is not taken into account in the standard meteorological data which usually gives only the absolute broadband global irradiance [2]. The physical behaviour of solar cells and photovoltaic modules under varying solar illumination and changing ambient temperature needs to be known. Usually these data are not provided by the manufacturers and suppliers of PV products. Moreover, the data provided most often are taken at test conditions which hardly ever occur in practice [3].
The importance of spectral effects on PV devices has been investigated by other authors such as Gottschalg et al. [2] and Kenny et al. [4], on the basis of computer simulations and indoor measurements. Most of the investigations reported have been based on “useful fractions”, defined as the ratio of the observed spectral irradiation in the useful spectral range of the PV device in question to the observed global irradiance [2] and [5]. In this paper, we present the quantitative effects of the solar spectral variations on the device performance of two modules with different PV technologies, i.e. copper indium diselenide (CIS) and multi-crystalline silicon (mc-Si). The data used are based on outdoor measurements on cloud-free days.