Intrinsically Stretchable Organic Photovoltaic Thin Films Enabled by Optimized Donor–Acceptor Pairing
Xuanang Luo, Guillaume Freychet, Ziqi Gan, Kang An, Huijun Du, Cheng Wang, Ning Li, Wenkai Zhong, Lei Ying
Abstract
The development of efficient stretchable organic photovoltaics (OPVs) poses a challenge that requires addressing the coupling of morphology and electronic structure in donor/acceptor blended thin films, which represents the interplay between mechanical deformation and photophysical performance. In this study, intrachain modification is employed to enhance the stretchability of conjugated polymers PTzBI-Si and P(NDI2OD-T2), which is a well-studied donor/acceptor combination in all-polymer solar cells. By introducing segments 1,2-di(thiophen-2-yl)ethene and 1,8-di(thiophen-2-yl)octane, the crack-onset strains of the polymer are significantly increased. This effect is achieved by randomizing the local intrachain conformation and tuning the crystalline packing and chain aggregation. The donor/acceptor pairing of the modified polymers is evaluated with their OPV performance, where the combination of PO-5:NV-10 shows well-balanced stretchability and performance. With the morphological optimization by the addition of the solvent additive dibenzyl ether, the PO-5:NV-10 thin film exhibits 1 order of magnitude increase in the crack-onset strain, surpassing 20%, along with a device efficiency of 8.45%, comparable to that of the reference blend. These findings highlight the importance of the optimal selection of donor/acceptor pairs in achieving intrinsically stretchable OPVs without compromising efficiency.