Side-Chain-Functionalized Poly(indacenodithiophene-alt-benzothiadizole)s as Stretchable High-Mobility Semiconductors with Improved Elasticity

Abstract

To regulate the mechanical properties of poly-(indacenodithiophene-alt-benzothiadizole) (IDT-BT), a highmobility polymer semiconductor with high ductility but inferior elasticity (plastic deformation onset strain (PdOS) < 10%), triisopropylsilyl (TIPS), hydroxyl (OH), and 2-ureido-4[1H]pyrimidone (UPy) groups were introduced into its side chain ends. The incorporation of bulky and neutral TIPS groups led to slightly increased ductility but had no obvious influence on the elasticity of the polymer. The presence of OH groups resulted in enhanced elasticity without sacrificing ductility. However, highcontent (20 mol %) OH-functionalized side chains were necessary to improve PdOS to above 30% due to the weak and dynamic nature of formed hydrogen bonds. In contrast, incorporating a small amount of UPy groups, capable of forming strong quadruple hydrogen bonds, in side chains could significantly improve the elasticity of the polymer. A PdOS of above 40%, along with a crack onset strain of ∼100% and decent hole mobility of ∼0.6 cm 2 V −1 s −1 , was demonstrated for polymer UPy-5% that contained 5 mol % UPy-functionalized side chains. Because of excellent elasticity, UPy-5% films displayed stable mobility against cyclic stretching, releasing up to 500 cycles at a tensile strain of 30%.

Investigating the Effects of Hydrogen Bonding on Mechanical and Electrical Properties of n-Type Semicrystalline Polymers

“…Recent studies have shown that H-bonding units featuring nucleobase-derived structures, such as thymine (Thy), ureidopyrimidinone, and diaminopyrimidine (Dap), are particularly effective due to their ability to engage in multipoint H-bonding. ,,, These units form dimeric interactions, significantly enhancing the H-bonding effects in the conjugated polymers. Additionally, positioning these units at the end of side chains in a pendant-type structure has proven to be a successful approach to retain the overall conjugation of the polymer backbone, thus preserving the essential electronic properties of the polymers. ,, For instance, we have demonstrated the benefits of strategically incorporating Thy units at the end of the side chains of PM7-based conjugated copolymer donors, which facilitated H-bonding-assisted intermolecular interactions without disturbing the electronic performance . The resulting intrinsically stretchable organic solar cells (IS-OSCs) achieved a high power conversion efficiency (PCE) of 13.7% and exhibited excellent stretchability, maintaining 80% of their initial PCE even at 43% strain.…”