Smart geometrical approach to intercalate a highly absorbing and quite resistive electron donor layer in ternary organic photovoltaic cells

Ternary organic photovoltaic cells (OPVs) have been shown to be a promising approach to increase cells efficiency through broadening of their absorption range. Often, ternary cells are based on a blend of two donors and one acceptor, the efficiency of planar ternary heterojunction being limited by the resistance of the three stacked layers. Here, we show that by depositing the intercalated layer through a grid we are able to decrease significantly the series resistance of the device, while the use of two donors allows improving the short circuit current and the efficiency of the organic photovoltaic cells. Electrical, optical and morphological studies show the ternary cell behaves like parallel OPVs. The first donor layer consists in an AlPcCl film, the acceptor layer is a C60 film while the central layer consists in a laboratory made molecule called MD2. If the MD2 layer absorbs strongly the light and permits to the both types of carrier to diffuse, its carriers mobility is small. Therefore, the discontinuities, due to the grid, of the MD2 intercalated layer allow improving the cells efficiency over-passing the corresponding binary cells performances. [Display omitted] •New donor: 2-((5-(4(diphenylamino)phenyl)thiophen-2-yl)methylene)malononitrile (MD2).•Modest carrier mobility of MD2 limits ternary OPV performances.•Smart geometrical approach permits ternary OPVs to behave like independent parallel structures.•AlPcCl/MD2/C60 ternary PHJ-OPV performances overpass that of corresponding binary OPV.