"Here is reported ananalysis of the external and internal quantum efficiency (EQE and IQE) and, its correlation with the power conversion efficiency (PCE) of organic photovoltaic (OPV) cells, as a function of the active layer thickness, ranging from 40 to 165 nm. OPVs cells configuration was ITO/PEDOT:PSS/PTB7-Th:PC71BM/PFN/Field’s Metal (FM: an alternative top electrode). IQE spectra were determined from EQE and net internal absorption spectra; net absorption was estimated through the transfer matrix method (TMM)."