Identification of transport and recombination paths in homo and heterojunction silicon solar cells by electrically detected magnetic resonance

We report on a first study of electrically detected magnetic resonance (EDMR) on crystalline silicon (c-Si) solar cells with gas-phase deposited n-type amorphous (a-Si:H) and c-Si emitters (epi-Si). The spectra of epi-Si emitter cells have at least five EDMR signals observed only under illumination with g values ranging from 1.99 to 2.01. The signals have two-fold symmetry and resemble shallow donors and Pbo-like centers known from the Si/SiO2 interfaces. In contrast, the EDMR signals in the spectra of the a-Si:H/c-Si cells are observed in the dark as well as in the photocurrent and stem from the a-Si:H layer. They can be identified with either recombination through neutral dangling bonds or hopping of electrons and holes in band tail states of the emitter layer. The hopping signals show a frequency dependence not observed before which is discussed in terms of a modified model for spin-dependent hopping in doped a-Si:H. (C) 2000 Elsevier Science B.V. All rights reserved.