Control of Effective Elastomer Density Enables Mechanically Robust and High-Efficiency Intrinsically Stretchable Organic Solar Cells.

Sun, Ming; Wang, Chen; Xiao, Mengfei; Sun, Fengbo; Wang, Hao; Xu, Yujie; Fu, Zhen; Zhang, Wenqing et al. · Adv Mater · 2026

basic_science · Level V

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Abstract

Intrinsically stretchable organic solar cells (IS-OSCs) are highly promising for next-generation wearable electronics. The incorporation of thermoplastic elastomers (TPEs) provides a cost-effective strategy to improve mechanical compliance. However, the influence of TPE structural diversity on device performance has been largely overlooked. In this work, the concept of effective elastomer density (D<sub>e</sub>) is introduced as a unified molecular descriptor to quantitatively evaluate how elastomer structures affect IS-OSC morphology and functionality. It is demonstrated that increasing D<sub>e</sub> enhances stretchability by inducing domain coarsening and surface roughening in amorphous regions, but simultaneously prolongs exciton lifetimes and suppresses charge extraction and transport. Notably, IS-OSCs achieve an optimal balance at a critical D<sub>e</sub> of 1.5 mol m<sup>-3</sup>, delivering a high initial power conversion efficiency (PCE) of 14.3% and retaining 80% of the initial PCE at 30.6% strain, representing the best performance reported to date for IS-OSCs employing the elastomer-plasticization strategy. This descriptor-based framework provides a predictive and generalizable guideline for the molecular design of elastomers in stretchable optoelectronic devices.