Photoluminescence and Electroluminescence from Amorphous Silicon/Crystalline Silicon Heterostructures and Solar Cells

Photoluminescence and electroluminescence from amorphous silicon / crystalline silicon heterostructures is a measure of the radiative band-to-band recombination, described in terms of the quasi-Fermi level splitting according to Planck’s generalised law, and the experiments thus probe the excess carrier densities in the crystalline silicon. Depending on the layer structure of the investigated sample, the contact-less photoluminescence experiment allows the characterisation of precursor structures for solar cell optimisation and for the study of related physical aspects like interface recombination. Both photoluminescence and electroluminescence experiments can be applied to solar cells for which the luminescence yield, or more precisely the deduced quasi-Fermi level splitting, can be related to the open-circuit voltage of the device which itself is limited by factors like the interface recombination rate. The coverage of luminescence techniques is complemented here by an account of modulated photoluminescence, a variant of the experiment, which may be used for the lifetime determination in wafer structures. Numerical modelling provides additional insight into the physics of interface recombination and its impact on the quasi-Fermi level splitting and thus the luminescence yield and the open-circuit voltage.