How does the spectral response of a thin-film PV module (e.g., CdTe) differ from that of a crystalline silicon (c-Si) module, and what implications does this have for energy yield in different geographic locations?

The spectral response of a PV module refers to its sensitivity to different wavelengths of light. Thin-film PV modules, such as Cadmium Telluride (CdTe), typically have a broader spectral response compared to crystalline silicon (c-Si) modules, particularly in the shorter wavelength (blue) region of the solar spectrum. Crystalline silicon tends to absorb longer wavelengths of light more effectively, while CdTe absorbs more across the entire visible spectrum and into the near-infrared. This difference in spectral response has implications for energy yield in different geographic locations because the solar spectrum varies depending on atmospheric conditions, latitude, and altitude. Locations with higher levels of diffuse light, such as those with frequent cloud cover or higher latitudes where sunlight passes through more atmosphere, tend to have a bluer spectrum (more shorter wavelengths). In these locations, CdTe modules can potentially generate more energy than c-Si modules because they are more efficient at converting blue light into electricity. Conversely, in locations with clear skies and direct sunlight, where the spectrum is redder (more longer wavelengths), c-Si modules may perform better. The spectral response also affects the temperature coefficient, where modules with broader spectral response are less impacted by temperature shifts that shift the spectral distribution.