Tandem Structure for Organic Photovoltaic Solar Cells

Background: UCF researchers have designed a new three terminal parallel structure with AZO as a common cathode. This tandem structure for organic photovoltaic solar cells provides a highly transparent common cathode for the tandem cell and ensures a perfect insulation between the two sub-cells so they can function independently. With the new structure both sub-cells are expected to function more efficiently because of the presence of a hole blocking layer (HBL) and electron blocking layer (EBL) as well as the better control of the work function of the anode through Ni-doping. This makes the structure universal compatible with different bulk heterojunction sub-cells regardless of the conjugated polymer. This paves the road to a 10% efficiency device which meets the requirements to commercialize OPVs. Technology Description: This new technology from UCF consists of a back-to-back parallel tandem organic photovoltaic cell structure that includes a common cathode that separates two anodes within the parallel tandem organic photovoltaic cell structure. The presence of a very thin layer (approximately 1 nanometer) of a lithium fluoride material layer (LiF) provides ohmic contact for electrons from both of the back-to-back parallel tandem organic photovoltaic cell structures. Since the LiF is laminated to both sides of the AZO material layer the lowest unoccupied molecular orbital of an active material layer within the OPV cell structure is about −4.0 eV. The nickel and tin doped indium oxide material layer (Ni-ITO) anodes include a nickel component that provides a work function in a range from at least about −5.0 eV to about −5.4 eV. By using a p-type NiO as a hole transport layer and an EBL for both sub-cells and an intrinsic ZnO (i-ZnO) layer as a HBL on the other side of the active layer both layers are resistive to the formation of any short circuits/shunts. This design provides an enhanced hole extraction with transfer and collection ability of the organic photovoltaic cell device with the Ni-ITO anode. Applications: 1) Solar cells 2) Photovoltaic cell arraysPatent Status: US 2012/0060907 A1