Recombination in μc-Si:H pin solar cells

Abstract

Recombination in microcrystalline silicon (μc-Si:H) pin solar cells is studied by electrically detected magnetic resonance (EDMR). The EDMR response of the pin cell under illumination shows a quenching resonance with identical line shape as found in undoped films with coplanar contact geometry even though the current path is perpendicular and parallel to the growth direction, respectively. At room temperature only a single line at g≈2.005 dominates. This line also appears in the dark forward current, however, with opposite sign. It is assigned to a direct-capture recombination at neutral dangling bonds (db) in the space charge region. At a bias above 0.6 V, however, the EDMR signal disappears. This behavior is indicative of diffusion-limited charge collection as is known from EDMR studies of c-Si pn solar cells and can be quantitatively described with a simple diffusion model that was developed for EDMR of crystalline silicon pn junctions.