Photovoltaic flexibles: integrating organic solar cells onto ETFE membrane

The application of wafer based Photovoltaics (PVs) have been long hindered by their high production, installation and maintenance costs, as well as their poor product design for building integration. The upcoming organic photovoltaic (OPV) with high processibility of active layer materials through Roll to Roll (R2R) printing technology exhibits as a promising alternative due to its low capital costs and better visual pleasing appearance. This potential has been enhanced by its recent efficiency and lifetime research progresses. Meanwhile, fluoropolymeric membrane materials like Ethylene tetrafluoroethylene (ETFE) and Polytetrafluoroethylene (PTFE) share higher popularity as a glass substitute in contemporary architecture context attributing to their extraordinary lightness, transparency and high flexibility. Coincidentally, most of the membrane material application occasions, including roofing and facade of large public buildings such as stadiums, exhibition hall, as well as building atrium and aisle roofs, are also the potential building integrated photovoltaic (BIPV) integration scenarios. PV-Flexible proposes a novel BIPV product solution by taking advantages of both PV technology’s renewable solar energy harvesting capability and easier architectural utilization of membrane substrates. This PhD research explores the possibility, difficulties and effectiveness of ETFE substrate printed OPV layers & cells. Far too little researches have investigated the design and development of PV-Flexibles, while its potential market segments has also not yet been well addressed. Current OPV layers are typically deposited on plastic substrates like Polyethylene terephthalate (PET) or Polyethylene naphthalate (PEN), resulting in inferior performance as architectural components. Even few works have been devoted to explore the performance of PV-Flexible in real application. In order to achieve better printing of OPV onto ETFE, the wettability of ETFE surface has been studied and pre-treatments to enhance it have been verified in this research. ETFE demands a high surface hydrophobicity, which leads to a bad printing quality of OPV electrode layers. Deposition of an extra Polymethylmethacrylate (PMMA) layer above the ETFE surface has been proven to be able to decrease its hydrophobicity. The oxygen plasma treatment has reached a much higher delamination load and has been evidenced to be more effective for a higher adhesiveness of PMMA layer on ETFE surface than the corona treatment. The responses of OPV layer composite under external loads have been investigated through experimental works with both commercial OPV modules and ETFE printed OPV layers, to understand better the weakness, the failure mechanism of OPV in strain and how this will influence its performance. The commercial organic module loses its effectiveness after meeting the critical strain of 1.8%, corresponding to a critical stress of 20MPa. The ETFE printed Ag electrode conductance is less sensitive than PET printed one with large strains. This research also implemented the experimental printing of prototype OPV cells onto ETFE substrate, and its performance characterization. The research outcomes revealed by this survey can provide valuable knowledge for future realization of easy printed, mechanically robust OPV on architectural membranes.