Temperature-dependent quantum efficiency analysis of recombination centers in silicon thin-film solar cells

We present temperature dependent quantum efficiency (TQE) as a new lifetime spectroscopy (LS) method for the analysis of recombination centers in thin film solar cells. Applying TQE to epitaxial silicon thin-film solar cells grown by ion-assisted deposition at low deposition temperatures T/sub dep/ (450/spl deg/C/spl les/T/sub dep//spl les/650/spl deg/C) unveils that the diffusion length in this material is dominated by Shockley-Read-Hall recombination via two relatively shallow defects with activation energies in ranges of 70-110 and 160-210 meV. At room temperature, the 200-meV defect dominates the material´s diffusion length and, in consequence, the photovoltaic device performance. A combination of TQE, deep level transient spectroscopy and minority carrier diffusion length data allows us to deduce an exponential decay of the defect density in the films with increased deposition temperature.