Band-edge electroluminescence of crystalline silicon heterostructure solar cells

Abstract

Monocrystalline Si solar cells exhibit above 50 K intrinsic electroluminescence which increases with temperature to external efficiencies beyond 0.03%. Spectra derived from the generalized Planck equation suggest that interface recombination is responsible for this temperature dependence. However, these modeled spectra predict too large emission above the gap. Spectra derived from the bandstructure and statistics of electrons, holes and phonons show that even at room temperature light is emitted only by creation of phonons while phonon annihilation does not contribute. The analysis suggests that detailed balance of absorption and emission rates is not achieved for emission at indirect gaps.