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.