At modern synchrotron radiation facilities, there is an increasing demand for experiments in hard X-ray energy range which are presently limited by detector efficiency. Therefore the development of new detectors or extension of present detectors has high priority. In this presentation we will show simulations of the detector response of pnCCD for hard x-ray photons up to about 120 keV including photoelectric effect and Compton scattering. This simulation will compared to measured data taken from a Laue diffraction experiment at EDDI beamline of BESSY II using a single crystal.