The outdoor dependence of temperature and diurnal irradiance on inverted organic photovoltaic (OPV) module performance has been analysed and benchmarked against monocrystalline-silicon (c-Si) photovoltaic technology. This is first such report and it is observed that OPVs exhibit poorer performance under low light conditions, such as overcast days, as a result of inflexion behaviour in the current-voltage curves, which limits the open-circuit voltage (VOC) and fill factor. These characteristics can be removed by photo-annealing at higher irradiance levels, which occur diurnally as irradiance increases after sunrise. We also report the first temperature coefficients for OPVs from outdoor data; the OPV modules showed a positive temperature coefficient, which compared to a negative coefficient from the c-Si modules. Overall, the cell degradation outdoors appears very severe for these modules and highlights the need for improved barrier.