Highly Conjugated Three-Dimensional Covalent Organic Frameworks Based on Spirobifluorene for Perovskite Solar Cell Enhancement

Highly conjugated three-dimensional covalent organic frameworks (3D COFs) were constructed based on spirobifluorene cores linked via imine bonds (<b>SP-3D-COFs</b>) with novel interlacing conjugation systems. The crystalline structures were confirmed by powder X-ray diffraction and detailed structural simulation. A 6- or 7-fold interpenetration was formed depending on the structure of the linking units. The obtained <b>SP-3D-COFs</b> showed permanent porosity and high thermal stability. In application for solar cells, simple bulk doping of <b>SP-3D-COFs</b> to the perovskite solar cells (PSCs) substantially improved the average power conversion efficiency by 15.9% for <b>SP-3D-COF 1</b> and 18.0% for <b>SP-3D-COF 2</b> as compared to the reference undoped PSC, while offering excellent leakage prevention in the meantime. By aid of both experimental and computational studies, a possible photoresponsive perovskite–<b>SP-3D-COFs</b> interaction mechanism was proposed to explain the improvement of PSC performance after <b>SP-3D-COFs</b> doping.