POS5-1097
Fused Selenophene and Side Chain Elongation Synergistically Enable Absorption Broadening and Morphology Control in Polymer Donors for Organic Solar Cells
When and Where
Nov 30, -0001
00:00 - 00:00
Presenter(s)
Junmo Kang (Department of Chemistry, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Republic of Korea)
Co-Author(s)
Abstract
Organic solar cells (OSCs) require polymer donors that provide broad light harvesting, favorable morphology, and sufficient solution processability. However, the benchmark donor D18 still suffers from limited absorption in the 600–700 nm region and relatively poor solubility, restricting photocurrent generation and morphology control. Here, we report fused selenophene-based polymer donors PDSeBT-BO and PDSeBT-HD, developed by selectively incorporating selenium into the fused acceptor unit of the D18 backbone and elongating the alkyl side chain through a concise 5-step route based on a facile SNAr reaction and direct selenocyclization. First, selenium incorporation broadens donor absorption toward the 600–700 nm region, where D18 and L8-BO show relatively weak absorption, thereby improving spectral coverage and enhancing the JSC contribution from this region. Importantly, this absorption broadening is accompanied by preferential LUMO stabilization while the HOMO level is largely maintained, allowing the improved JSC to be achieved with a modest VOC penalty. Second, side chain elongation to 2-hexyldecyl improves solubility and donor/acceptor miscibility with L8-BO, enabling finely distributed nanoscale phase separation, enhanced molecular ordering, and a well-defined p-i-n like vertical composition gradient in the pseudo-bilayer active layer. These morphological advantages facilitate exciton dissociation, balanced charge transport, and suppressed recombination, leading to simultaneous improvements in JSC and FF. Consequently, the PDSeBT-HD/L8-BO device achieves a PCE of 19.07%, among the highest reported for binary OSCs based on newly developed polymer donors. This work highlights fused selenophene incorporation combined with side chain elongation as a synthetically accessible and effective strategy for advancing high-performance polymer donor design.
