Covalent Organic Framework-Incorporated MAPbI3 for Inverted Perovskite Solar Cells with Enhanced Efficiency and Stability

The study synthesized triazine-based covalent organic framework (COF) materials (TPTP-COF, TPBT-COF, and TPBTz-COF) to be used as defect passivation additives in methylammonium lead iodide (MAPbI₃)-based inverted perovskite solar cells (PVSCs). The frameworks of the COFs in the MAPbI₃ layer can serve as a template for the crystal growth of perovskite, repairing crystal defects, enhancing the quality of the crystal film, and stabilizing perovskite materials. In addition to the conjugation intensity of the COFs, the average particle size of the COF in the precursor solution of the perovskite significantly influences the morphology, optical properties, and photovoltaic characteristics of the COF/MAPbI₃ blend films used in PVCs. The crystal grain size, X-ray diffraction intensity, PL intensity, carrier lifetime, and charge mobility were improved in the MAPbI₃ films when the COF was incorporated, particularly with the TPBTz-COF, compared to the original MAPbI₃ film. The photovoltaic performance and stability of the PVSCs containing the COF were enhanced compared to the PVSCs based on pristine MAPbI₃. The structure of the inverted PVSCs included indium tin oxide/NiO_x/COF (TPTP-COF, TPBT-COF, or TPBTz-COF):MAPbI₃/PC₆₁BM/bathocuproine/Ag. TPBTz-COF exhibited the highest power conversion efficiency (PCE) among the COF additives, achieving a PCE of 20.04%, an open-circuit voltage of 1.04 V, a short-circuit current density of 24.26 mA cm^–1, and a fill factor of 79.40%. The TPBTz-COF-based PVSC maintained 80% of its original power conversion efficiency after being stored for 400 h under ambient conditions (30 °C; 60% relative humidity).