Photovoltaics (PV) hold tremendous potential as a technology to address the rising global demand for clean energy. One key for wide-spread success of this technology is to drive down the cost per Watt of electricity. This requires utilisation of less energy-intensive/lower cost production methods. One highly promising emerging technology for this is organic photovoltaics (OPVs). OPVs promise large-area manufacturing of future products by high-throughput roll-to-roll processing in ambient conditions. OPVs have also seen a rapid improvement in performance over recent years with certified devices reaching 10% power conversion efficiency. However there still remain fundamental questions related to the exact microstructure that needs to be realised within the active layer of such solar cells to optimise – and further improve – their power conversion efficiency. A structural picture is also necessary to target specific processing protocols and permit reliable device fabrication at high yield. The active layer of bulk-heterojunction (BHJ) OPVs is comprised of a blend of an electron-donating and an electron-accepting material, which until recently were generally believed to form relatively pure phases. However new studies have indicated that the BHJ microstructure may also contain a phase, where both materials can be mixed at much more intimate scales. Here, we discuss the role of this intermixed phase. We show that relative straight-forward techniques, such as photoluminescences and UV-vis spectroscopy provide highly valuable insight in the structural features of these systems and propose, based on a series of structurally well-defined blend architectures, a strong influence of the presence of such an intermixed phase on the opto-electronic processes of the system and provide structural guidelines for further improving the efficiency of BHJ OPVs.<br/>

On the role of intermixed phases in organic photovoltaic blends

251st National Meeting (2016)

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