Electro- and photo-luminescence spectra from a-Si : H and a-SiGe p-i-n solar cells

Electroluminescence (EL) and photoluminescence (PL) spectroscopies were use d to study the effects of hydrogen dilution on a-Si:H and of varying Ge con tent on aSiGe p-i-n cells. We found that (a) in the case of hydrogen diluti on, the EL peak energy (ELpeak) increased with H-dilution that correlated w ith an increase of open circuit voltage (V-oc), but the corresponding PL pe ak energy (PLpeak) did not change; and (b) different from observations that ELpeak < PLpeak, the ELpeak can be the same or larger than the PLpeak. The results were explained by the model of dispersive-transport controlled rec ombination for EL. We suggest that the V-oc is not only related to the opti cal gap and the tail states but also to the transport processes. (C) 2000 E lsevier Science B.V. All rights reserved.