Intrinsically Stretchable Organic Solar Cells on Crack-Free Substrate/Electrode Platform under 40% Strain

The increasing demand for off-grid power sources in soft robotics and wearable electronics has sparked considerable interest in stretchable organic solar cells (SOSCs). However, the brittleness of materials used in traditional solar cells makes them susceptible to cracks even under mild strain, limiting their application in wearable devices. To overcome this limitation, intrinsically stretchable organic solar cells (IS-OSCs) have emerged as a promising solution. They offer advantages, including omnidirectional stretchability, seamless integrability, and compatibility with conventional manufacturing processes. In our study, we revealed that the mechanical failure of IS-OSCs under strain can be traced back to the PH1000 layer. Cracks originating from the PH1000 layer subsequently propagate to the photoactive layer, resulting in a decrease in power conversion efficiency (PCE) in the IS-OSCs under strain. To achieve crack-free IS-OSCs under human body elongations as high as ~40%, we propose a double-locked substrate/transparent electrode platform. To enhance the adhesion of the most fragile layer, the PH1000 layer, we developed techniques to enhance both physical and chemical adsorption, including surface treatment of the substrate and cross-linking between the substrate and modified PH1000. Remarkably, our double-locked system sustained strains exceeding 40% without developing cracks, while the untreated PH1000 film exhibited cracks at a strain level of 20%. Our double-locked IS-OSCs achieved an initial PCE of 10.2%, demonstrating significantly enhanced mechanical robustness, with nearly double the ε_PCE70 (44%) compared to the control device (24%), where ε_PCE70 represents the strain at which 70% of the initial PCE is retained¹. Additionally, our IS-OSCs maintained 90% of the initial PCE even after undergoing 1,000 stretch-release cycles under a 10% strain.