Why are acceptance angle of Pm and Isc different in spite of uniform illumination onto concentrator solar cells?

The acceptance angle of concentrator modules measured by short circuit current Isc is always larger than that by maximum power Pm even by use of advanced concentrator optics that keep uniform illumination onto the concentrator cells. The purpose of this study is to investigate the cause of that myth. An expanded Monte Carlo method that calculates acceptance angle of CPV modules was developed with considering 2-dimensional misalignment error vector. It was shown that the gap from Pm-based acceptance angle from that of Isc-based was a function of deviation of assembles misalignment in the module. The rough rule for acceptable assembles misalignment is that the standard deviation of assemble misalignment level will be less than 10 % of acceptance angle of the optics.