An end-capped strategy for crystalline polymer donor to improve the photovoltaic performance of non-fullerene solar cells

The effects of end-capped modifications of a polymer donor with high molecular weight on non-fullerene solar cells are largely ignored, even if the chain-end-functionalized method of conjugated polymers is an effective strategy in modulating polymeric optical-electronic properties. In this study, we design and synthesize an end-capped polymer, PM6TPO, via a reaction with the parent polymer PM6. Meanwhile, the conventional detection methods of X-ray photoelectron spectroscopy (XPS), matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF), and 1H nuclear magnetic resonance (1H NMR) were replaced by simple solution-based inductively coupled plasma-mass spectrometry (ICP-MS) to evaluate the end-capped efficacy of PM6TPO. By introducing end-capped groups on a high molecular weight polymer donor, we could finely tune the aggregated behavior, strengthen the miscibility between the donor and acceptor without sacrificing the strong aggregated properties, and reduce the non-radiative recombination with a lower energy loss. Therefore, the PM6TPO-based organic solar cell (OSC) realized a higher open-circuit voltage of 0.843 V and PCE of 17.26% than that of the non-end-capped parent polymer, PM6 (0.824 V and 16.21%, respectively). This work not only provides a straightforward method for verifying the end-capped efficacy of a high molecular weight polymer but also indicates a new research direction for improving the photovoltaic performance of non-fullerene-based solar cells.