This letter introduces a novel approach estimating the power conversion efficiency (PCE) of a square luminescent solar concentrator (LSC) by point excitations on the “optical centers” as proposed here. Predicted by theoretical calculations, photoluminescence emissions from these optical centers experience almost the same average optical path with those from the whole device under uniform illumination. This is experimentally verified by a 20 x 20 cm2 silicon quantum dots-based LSC, with only ~5% errors between the...