Lead Iodide Perovskite Sensitized All-Solid-State Submicron Thin Film Mesoscopic Solar Cell with Efficiency Exceeding 9%

Abstract

We report on solid-state mesoscopic heterojunction solar cells employing nanoparticles (NPs) of methyl ammonium lead iodide (CH ₃NH ₃)PbI ₃ as light harvesters. The perovskite NPs were produced by reaction of methylammonium iodide with PbI ₂ and deposited onto a submicron-thick mesoscopic TiO ₂ film, whose pores were infiltrated with the hole-conductor spiro-MeOTAD. Illumination with standard AM-1.5 sunlight generated large photocurrents (J _SC) exceeding 17 mA/cm ², an open circuit photovoltage (V _OC) of 0.888 V and a fill factor (FF) of 0.62 yielding a power conversion efficiency (PCE) of 9.7%, the highest reported to date for such cells. Femto second laser studies combined with photo-induced absorption measurements showed charge separation to proceed via hole injection from the excited (CH ₃NH ₃)PbI ₃ NPs into the spiro-MeOTAD followed by electron transfer to the mesoscopic TiO ₂ film. The use of a solid hole conductor dramatically improved the device stability compared to (CH ₃NH ₃)PbI ₃ -sensitized liquid junction cells.