Ultra-High Voltage Multifunction Organic Solar Cells for Low-Power Electronic Applications

摘要

Low power electronics are an ideal application for organic photovoltaics (OPV) where a low-cost OPV device can be integrated directly with a battery to provide a constant power source. We demonstrate ultra-high voltage small molecule multifunction devices with open circuit voltage (V_(OC)) values of up to 7V. Optical modelling is employed to aid the optimisation of the complex multi-layer stacks and ensure current balancing is achieved between sub-cells, and optimised multijunction devices show power conversion efficiencies of up to 3.4% which is a modest increase over the single junction devices. Sub-cell donor/acceptor pairs of boron subphthalocyanine chloride (SubPc)/ fullerene (C_(60)) and SubPc/ Cl_6-SubPc were selected both for their high V_(OC) in order to minimise the required number of junctions, but also for their absorption overlap to reduce the spectral dependence of the device performance. As a result, the devices are shown to directly charge a micro-energy cell type battery under both low illumination intensity white light and monochromatic illumination.