Achieving Record-High Stretchability and Mechanical Stability in Organic Photovoltaic Blends with A Dilute-Absorber Strategy

Organic solar cells (OSCs) offer a unique advantage over other photovoltaic technologies in terms of flexibility. To realize high-performance stretchable and wearable OSCs, apart from high power conversion efficiency (PCE), they must also have excellent tensile properties and mechanical stability, whereas the present metrics of photovoltaic films can hardly meet the application requirements. The stretchability and mechanical stability of active layer blend films are crucial for intrinsically stretchable devices that can work effectively under stress. Herein, we put forward a facile yet low-cost strategy to construct intrinsically stretchable OSC active layers by introducing a readily accessible polymer elastomer as a diluent to the organic photovoltaic blends. Remarkably, record-high stretchability with fracture strain up to 1000% and mechanical stability with elastic recovery&gt;90% under cyclic tensile tests are realized in OSC active layers for the first time. Specifically, the tensile properties of best-performance all-polymer photovoltaic blends can be increased by up to 250 times after blending. Previously unattainable performance metrics (fracture strain &gt;50%, PCE &gt;10%) are simultaneously achieved in the resulting photovoltaic films. Furthermore, an overall evaluation parameter <i>y</i> is proposed for the efficiency-cost-stretchability balance of organic photovoltaic blend films. The <i>y</i> value of our dilute-absorber photovoltaic system is two orders of magnitude greater than the prior state-of-the-art. With the help of advanced neutron scattering and X-ray scattering techniques, the microstructure-mechanical performance/stability relationships of intrinsically stretchable OSCs are established.