Improved fill factors in amorphous silicon solar cells on zinc oxide by insertion of a germanium layer to block impurity incorporation

Amorphous silicon based solar cells deposited on zinc oxide (ZnO) exhibit reduced fill factor and open circuit voltage in comparison with tin oxide (SnO2). One approach has been to use higher conductivity nanocrystalline layers to overcome the "higher contact resistance." Recent measurements have found the ZnO-p-layer contact resistance to be unchanged relative to SnO2, while instead, the diode ideality factor is poorer on ZnO. We show that the insertion of a thin, amorphous germanium layer at the ZnO-p-layer interface improves the cell performance and diode ideality factor by suppression of oxygen and zinc incorporation in the silicon layers. (C) 2004 American Institute of Physics.