Definitely the work function of electrodes is one side of the coin. The other side is that we can use the stable inorganic counter parts such as ZnO/TiO2/.. as the ETL layers and MoOx/CuSCN/.. as HTL layers in broad class of in the inverted BHJ solar cells. This allows to replace the PEDOT:PSS acidic reaction with the active layers. The matching of energy levels in inverted configuration is the added advantage. The Ag electrode is prone to vary its work function upon the direct illumination in the planar configuration, so there is possibility of series resistances/leakage currents at the electrode interfaces. This inverted configuration solves the above. So is why more potential research in the inverted configuration..