Abstract 

Intrinsically stretchable organic solar cells (IS-OSCs) have recently been spotlighted for their omnidirectional stretchability, seamless integrability to any surface, and facile fabrication. Due to these attributes, IS-OSCs are ideal off-grid power sources, especially for wearable electronics in real-life. However, under human body elongation as high as ~ 40 %, the cracks of IS-OSCs have been considered inevitable, and the origin of the mechanical failure has rarely been identified. Herein, we first clarify the crack-initiation and the propagation mechanism. Based on this, the crack-free substrate/transparent electrode platform for stretchable electronics is also suggested. We introduce a double-locking scheme, which reinforces the physical/chemical adsorption within the most mechanically fragile layer, a poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) and also with thermoplastic polyurethane (TPU) substrate. As a result, the crack-onset strain (COS) of double-locked IS-OSCs surpasses 40 %, while that of pristine ones was less than 20 %. The IS-OSCs with the double-locked system exhibit an efficient power conversion efficiency (PCE) of 10.2 %, and the absence of cracks allows the IS-OSCs to maintain 79.7 % of the initial PCE at 40 % strain.