  Organic semiconductors possess an intrinsic energetic disorder
characteristic, which holds an exceptionally important role for understanding
organic photovoltaic (OPV) operation and future optimization. We performed
illumination intensity dependence of capacitance-voltage (C-V) measurements in
PIDTDTQx:PC70BM based organic bulk heterojunction (BHJ) photovoltaics in
working conditions. Energetic disorder profiles for the photo-active layer,
PIDTDTQx:PC70BM, changed significantly when different interfaces were involved.
The effects of energetic disorder that could be reflected from C-V profiles are
incorporated through an exponential or Gaussian model of density of states
(DOS), or a combination of these two. Results underlie that an identical
organic blend in BHJ solar cells exhibits different energetic disorder when it
interacts with various interfaces. It may, thus, has a certain impact on OPV
performances, such as open-circuit voltage (V_oc ). Our study provides device
physicists a different perspective view for tailoring the organic energetic
disorder parameter via interfaces in order to enhance photo-electron conversion
efficiencies (PCE).
