Cellulose Nanocrystal-Incorporated MAPbI3 for Inverted Perovskite Solar Cells with Enhanced Efficiency and Stability

Abstract

Herein, cellulose nanocrystals (CNCs) were added to the MAPbI₃ layer to enhance the photovoltaic properties of MAPbI₃-based inverted perovskite solar cells (PVSCs). The addition of CNCs to the perovskite active layer helps repair crystal defects, improves crystal quality, and stabilizes the perovskite film structure by forming hydrogen bonds between hydroxyl groups and MAPbI₃. This defect passivation by CNCs leads to the formation of larger and denser crystal grains along with enhanced light absorption in the CNC-doped perovskite films. Consequently, trap density is reduced and carrier recombination is suppressed, thereby improving the power conversion efficiency (PCE) and stability of the CNC-doped PVSCs. The structure of the CNC-based inverted PVSCs comprises fluorine-doped tin oxide/NiO_x/CNC:MAPbI₃/PC₆₁BM/BCP/Ag. The CNC-doped PVSC demonstrated an open-circuit voltage (V_OC) of 1.07 V, a short-circuit current density (J_SC) of 24.43 mA cm^–2, a fill factor (FF) of 76.1%, and a PCE of 19.90%. Furthermore, the insertion of copolyacrylamide (PMD25) at the interface between the perovskite active layer and the NiO_x-based hole-transport layer effectively reduced the number of interfacial crystal defects. The MAPbI₃ layer deposited on PMD25-modified NiO_x exhibited denser crystal packing and higher carrier mobility, achieving a V_OC of 1.08 V, a J_SC of 25.03 mA cm^–2, an FF of 76.7%, and a PCE of 20.72%. Additionally, the CNC-doped PVSC, protected with a hydrophobic electrospun PVDF-HFP film, retained 80% of its initial PCE after storage for 600 h under ambient conditions (30 °C, 50% relative humidity).