Rigid- and soft-block-copolymerized conjugated polymers enable high-performance intrinsically stretchable organic solar cells

High power conversion efficiency (PCE) and mechanical robustness are dual requisites for wearable applications of organic solar cells (OSCs). Here, we simultaneously achieve high electronic and mechanical performances in OSCs using conjugated polymer donors (PDs) consisting of electroactive rigid and soft blocks. Specifically, we integrate rigid and soft blocks to synthesize block-copolymerized PDs (D180.8-s-PEHDT0.2) having an appropriate molecular weight of D18 blocks to reach the effective conjugation length and of PEHDT blocks to achieve high mechanical properties. As a result, the D180.8-s-PEHDT0.2 OSCs achieve excellent PCE (19.0%) and stretchability (crack-onset strain [COS] = 17.2%), thus overcoming the trade-off between the photovoltaic and mechanical properties in D18- (PCE = 18.1% and COS = 1.5%) and PEHDT-based OSCs (PCE = 5.0% and COS = 30.7%). Consequently, the D180.8-s-PEHDT0.2-based intrinsically stretchable (IS)-OSCs achieve both a high PCE (14.3%) and excellent stretchability (preserving 80% of the initial PCE at 31% strain).