"Here is reported the analysis of the external quantum efficiency (EQE or IPCE) and, its correlation with the power conversion efficiency (PCE) of organic photovoltaic (OPV) cells, as a function of the active layer thickness. OPVs cells configuration was ITO/PEDOT:PSS/Active layer/PFN/Field’s Metal (FM). The active layer was PTB7-Th:PC71BM blend. Active film thickness range was 40-165 nm. Internal quantum efficiency (IQE) was also estimated."