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).