RESUMEN
Designing new polymer semiconductors for intrinsically stretchable polymer solar cells (IS-PSCs) with high power conversion efficiency (PCE) and durability is critical for wearable electronics applications. Nearly all high-performance PSCs are constructed using fully conjugated polymer donors (PD) and small-molecule acceptors (SMA). However, a successful molecular design of PDs for high-performance and mechanically durable IS-PSCs without sacrificing conjugation has not been realized. In this study, we design a novel thymine side chain terminated 6,7-difluoro-quinoxaline (Q-Thy) monomer and synthesize a series of fully conjugated PDs (PM7-Thy5, PM7-Thy10, PM7-Thy20) featuring Q-Thy. The Q-Thy units capable of inducing dimerizable hydrogen bonding enable strong intermolecular PD assembly and highly efficient and mechanically robust PSCs. The PM7-Thy10:SMA blend demonstrates a combination of high PCE (>17%) in rigid devices and excellent stretchability (crack-onset value >13.5%). More importantly, PM7-Thy10-based IS-PSCs show an unprecedented combination of PCE (13.7%) and ultrahigh mechanical durability (maintaining 80% of initial PCE after 43% strain), illustrating the promising potential for commercialization in wearable applications.
RESUMEN
High power conversion efficiency (PCE) and stretchability are the dual requirements for the wearable application of polymer solar cells (PSCs). However, most efficient photoactive films are mechanically brittle. In this work, highly efficient (PCE = 18%) and mechanically robust (crack-onset strain (COS) = 18%) PSCs are acheived by designing block copolymer (BCP) donors, PM6-b-PDMSx (x = 5k, 12k, and 19k). In these BCP donors, stretchable poly(dimethylsiloxane) (PDMS) blocks are covalently linked with the PM6 blocks to effectively increase the stretchability. The stretchability of the BCP donors increases with a longer PDMS block, and PM6-b-PDMS19k :L8-BO PSC exhibits a high PCE (18%) and 9-times higher COS value (18%) compared to that (COS = 2%) of the PM6:L8-BO-based PSC. However, the PM6:L8-BO:PDMS12k ternary blend shows inferior PCE (5%) and COS (1%) due to the macrophase separation between PDMS and active components. In the intrinsically stretchable PSC, the PM6-b-PDMS19k :L8-BO blend exhibits significantly greater mechanical stability PCE80% ((80% of the initial PCE) at 36% strain) than those of the PM6:L8-BO blend (PCE80% at 12% strain) and the PM6:L8-BO:PDMS ternary blend (PCE80% at 4% strain). This study suggests an effective design strategy of BCP PD to achieve stretchable and efficient PSCs.
RESUMEN
Intrinsically stretchable organic solar cells (IS-OSCs), consisting of all stretchable layers, are attracting significant attention as a future power source for wearable electronics. However, most of the efficient active layers for OSCs are mechanically brittle due to their rigid molecular structures designed for high electrical and optical properties. Here, a series of new polymer donors (PD s, PhAmX) featuring phenyl amide (N1 ,N3 -bis((5-bromothiophen-2-yl)methyl)isophthalamide, PhAm)-based flexible spacer (FS) inducing hydrogen-bonding (H-bonding) interactions is developed. These PD s enable IS-OSCs with a high power conversion efficiency (PCE) of 12.73% and excellent stretchability (PCE retention of >80% of the initial value at 32% strain), representing the best performances among the reported IS-OSCs to date. The incorporation of PhAm-based FS enhances the molecular ordering of PD s as well as their interactions with a Y7 acceptor, enhancing the mechanical stretchability and electrical properties simultaneously. It is also found that in rigid OSCs, the PhAm5:Y7 blend achieves a much higher PCE of 17.5% compared to that of the reference PM6:Y7 blend. The impact of the PhAm-FS linker on the mechanical and photovoltaic properties of OSCs is thoroughly investigated.