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 (P D ) and small-molecule acceptors (SMA). However, a successful molecular design of P D s 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 P D s (PM7-Thy5, PM7-Thy10, PM7-Thy20) featuring Q-Thy. The Q-Thy units capable of inducing dimerizable hydrogen bonding enable strong intermolecular P D 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.

Polymer solar cells, with the assistance of nonfullerene acceptors (NFAs) and ternary blend strategies, have exceeded 18% power conversion efficiency. However, most NFA-based ternary blends are constructed using the strategies developed for polymer–fullerene systems, and intrinsic properties of these NFAs have been overlooked when designing a ternary organic solar cell. Here, using a new NFA 2,2′-((4,4,9,9-tetrahexyl-4,9-dihydro-s-indaceno[1,2-b:5,6-b′]dithiophene-2,7-diyl) bis(methaneylylidene)) bis(1H-indene-1,3(2H)-dione), referred to IDID, as the third component, we observed the appearance of a polymorph of IDID when it was introduced into a PTQ10: PC61BM binary blend and this ternary blend solar cell showed a significant improvement in efficiency from 3.38% to 6.04%. This relative increase (with respect to the best binary cell) is nearly 80% which is the highest among all the reported organic ternary blends to the best of our knowledge. Specifically, IDID was found to be nucleated by the host polymer donor PTQ10 under the assistance of the processing solvent to form a distinct polymorph, as proven by grazing incidence X-ray diffraction (GIXRD), differential scanning calorimetry (DSC), and supported by surface energy measurements. More interestingly, IDID, as a third component in the PTQ10: PC61BM system, was found to outperform the structurally similar NFA IDIC, which only boosted the efficiency from 3.38% to 3.55% in ternary polymer solar cells. This work highlights polymer-mediated polymorphism in NFAs as an important consideration in selection of components for and the optimization of ternary organic solar cells.

Recent work on non‐conjugated pendant electroactive polymers (NCPEPs) has demonstrated significant impacts of structural parameters such as backbone stereoregularity and the spacer connecting the pendant to the backbone on properties, most notably on charge carrier mobilities. Tuning of the pendant group however has not been reported for stereoregular NCPEPs. Here we present a family of novel isotactic poly((carbazolyl‐alkyl‐triazolyl)methyl methacrylates) (PCzATMMAs) for which the effects of increasing the pendant group from carbazole to 3,6‐bis(4‐(2‐ethylhexyl)thiophen‐2‐yl)‐carbazole were investigated. Based on unsuccessful post‐polymerization functionalization with this extended group via previously reported transesterification and thiol‐ene methodologies, we report functionalization via copper‐catalyzed azide‐alkyne cycloaddition which was demonstrated to be highly effective. The effect of spacer length was also investigated for comparison with previously established effects with alkyl spacers. Within the family of PCzATMMAs, hole mobilities were found to increase with longer spacer length and with thermal annealing. The incorporation of an extended pendant with alkyl solubilizing chains was found to result in a lower hole mobility than the equivalent polymer with an unfunctionalized pendant group. Importantly, the copper catalyzed azide‐alkyne cycloaddition proved to be an effective method of post‐polymerization functionalization for stereoregular NCPEPs when extending beyond a simple carbazole pendant.