Local junction voltages and radiative ideality factors of a-Si:H solar modules determined by electroluminescence imaging

摘要

In this contribution, we show that the dominant electroluminescent emission of hydrogenated amorphous silicon (a-Si:H) thin-film solar cells follows a diode law, whose radiative ideality factor n_Γ is larger than one. This is in contrast to crystalline silicon and Cu(In, Ga)Se_2 solar cells for which n_Γ equals one. As a consequence, the existing quantitative analysis for the extraction of the local junction voltage V_j(r) from luminescence images fails for a-Si:H solar cells. We expand the existing analysis method, and include the radiative ideality factor n_Γ into the model. With this modification, we are able to determine the local junction voltage V_j(r) for a-Si:H solar cells and modules. We investigated the local junction voltage V_j(r) and the radiative ideality factor n_Γ for both initial and stabilized a-Si:H solar modules. Furthermore, we show that the apparent radiative ideality factor is affected by the spectral sensitivity of the used camera system.