We report the influence of an exciton-blocking layer
and/or an Al2O3 thin layer at the interface “organic
acceptor/aluminium” on the efficiency of CuPc/C60 based photovoltaic
cells. The presence, or not, of a thin Al2O3 layer depends on the
encapsulating process of the devices. In the case of
glass/ITO/CuPc/C60/Al cells, the presence of an Al2O3 thin
layer at the interface “organic acceptor/aluminium” increases strongly the
open circuit voltage of the cells but decreases slightly their short circuit
current and fill factor. In the case of glass/ITO/CuPc/C60/Alq3/Al
cells, the open circuit voltage is systematically higher than without
Alq3. However, in that case, the presence of Al2O3 does not
improve significantly the cell performances. All these results are discussed
in terms of series and shunt resistance values related to possible oxygen
contamination and organic covalent action with the Al films. The
effectiveness of these different phenomena depends on the presence, or not,
of Alq3 and/or Al2O3 layers.