Highly mechanically stable and intrinsically stretchable large-area organic photovoltaics using nanoporous bulk-heterojunction

It is important to develop bulk-heterojunction films that simultaneously exhibit good photovoltaic properties and mechanical robustness to realize intrinsically stretchable organic photovoltaics (IS-OPVs). We developed a strategy for preparing nanoporous bulk-heterojunction (np-BHJ) films at a large area by nonsolvent-induced phase separation assisted by thermoplastic polyurethane. The resulting np-BHJ can form much improved adhesive interfaces with a neighbored stretchable layer in OPV devices and effectively dissipate applied mechanical stress. IS-OPVs using the np-BHJ films showed efficiency of 12.0 %, which is comparable performance to 12.4 % of the controlled BHJ. The IS-OPV device using np-BHJ films much improved mechanical stability and maintained 89 % of its initial efficiency under applied strain of 40 %. The corresponding module showed only 10 % decrease in efficiency after 1,000 cycles in stretching tests at 10 % strain. Because of high scalability of the npBHJ morphology, IS-OPV modules with efficiency of 7.06 % and active area of 10.17 cm2 2 and were successfully demonstrated. Photoplethysmography sensors prepared using the IS-OPV module showed strong potential for application in wearable electronics.