Voc-limiting recombination mechanisms in thin film silicon on glass solar cells

Recent studies of the lifetime and the injection level dependence of the open-circuit voltage (Suns-V_oc), and their temperature dependence, has led to the identification of two major V_oc limiting recombination routes in thin film polycrystalline silicon (poly-Si) on glass solar cells: 1) via the shallow bands at dislocations in the absence of deep levels; 2) at charged extended defects via deep levels. The first recombination mechanism limits the V_oc to a level that is insensitive to dopant density, while the second mechanism is predicted to degrade the V_oc as the dopant density drops below a certain value (~a few 10¹⁵cm^-3 at state-of-the-art). In addition, inhomogeneities in the bandgap further erode the V_oc in certain poly-Si cells deposited by e-beam evaporation.