We did not find out how to chose different technologies (such as monocristalline silicon, polycristallin silicon, thin film) for the PV Array. Is this possible? If not, could you please tell us which technology is used for the calculation?

HOMER models the PV array with some basic assumptions just a few parameters, such as rated capacity, derating coefficient, temperature coefficient, and so on.  Different PV technologies lead to different values for those parameters, but they are roughly correct for any non-concentrating technology.

Please refer to the help file for details on the assumptions and calculations that HOMER uses in calculating the PV array output.