Mechanical-robust and recyclable polyimide substrates coordinated with cyclic Ti-oxo cluster for flexible organic solar cells

With the rapid development of flexible optoelectronic devices, recyclability is highly desirable for alleviating resource waste and environmental pollution, but remains challenging. Here, a fully closed-loop recyclable crosslinked polyimide (RCPI) was fabricated via carboxyl ligand exchange between the CPI with pendent carboxyl groups and the cyclic Ti-oxo cluster (CTOC) with labile carboxyl ligands, which could be reconverted into reprocessable CPI and CTOC solution by pivalic acid. The RCPI-based embedded AgNWs@RCPI electrode shows comparable high conductivity, transparency and low roughness with ITO (indium tin oxide)/glass electrode, and meanwhile outstanding mechanical robustness. The related flexible organic solar cells (FOSCs) provided a high efficiency of 14.78% and maintained ~97% of the initial efficiency after 5000 bending cycles at a small bending radius of 1 mm. Moreover, the recyclability of the RCPI still retains after being manufactured into the FOSCs. This work provides a promising strategy for recyclable flexible optoelectronic devices.