Enhanced Photovoltaic Performance of Inverted Perovskite Solar Cells through Surface Modification of a NiO(x)-Based Hole-Transporting Layer with Quaternary Ammonium Halide–Containing Cellulose Derivatives

In this study, we positioned three quaternary ammonium halide-containing cellulose derivatives (PQF, PQCl, PQBr) as interfacial modification layers between the nickel oxide (NiO(x)) and methylammonium lead iodide (MAPbI(3)) layers of inverted perovskite solar cells (PVSCs). Inserting PQCl between the NiO(x) and MAPbI(3) layers improved the interfacial contact, promoted the crystal growth, and passivated the interface and crystal defects, thereby resulting in MAPbI(3) layers having larger crystal grains, better crystal quality, and lower surface roughness. Accordingly, the photovoltaic (PV) properties of PVSCs fabricated with PQCl-modified NiO(x) layers were improved when compared with those of the pristine sample. Furthermore, the PV properties of the PQCl-based PVSCs were much better than those of their PQF- and PQBr-based counterparts. A PVSC fabricated with PQCl-modified NiO(x) (fluorine-doped tin oxide/NiO(x)/PQCl-0.05/MAPbI(3)/PC(61)BM/bathocuproine/Ag) exhibited the best PV performance, with a photoconversion efficiency (PCE) of 14.40%, an open-circuit voltage of 1.06 V, a short-circuit current density of 18.35 mA/cm(3), and a fill factor of 74.0%. Moreover, the PV parameters of the PVSC incorporating the PQCl-modified NiO(x) were further enhanced when blending MAPbI(3) with PQCl. We obtained a PCE of 16.53% for this MAPbI(3):PQCl-based PVSC. This PQCl-based PVSC retained 80% of its initial PCE after 900 h of storage under ambient conditions (30 °C; 60% relative humidity).