Amide Additives Induced a Fermi Level Shift To Improve the Performance of Hole-Conductor-Free, Printable Mesoscopic Perovskite Solar Cells

Abstract

Solution-processable organic-inorganic perovskite solar cells have attracted much attention in the past few years. Energy level alignment is of great importance for improving the performance of perovskite solar cells because it strongly influences charge separation and recombination. In this report, we introduce three amide additives, namely, formamide, acetamide, and urea, into the MAPbI₃ perovskite by mixing them directly in perovskite precursor solutions. The Fermi level of MAPbI₃ shifts from -4.36 eV to -4.63, -4.65, and -4.61 eV, respectively, upon addition of these additives. The charge transfer between perovskite and mp-TiO₂ is found to be promoted as determined via TRPL spectra, and recombination in the perovskite is suppressed. As a result, the built-in electric field (<i>V</i>_bi) of the printable, hole-conductor-free mesoscopic perovskite solar cells based on these perovskites with amide additives is enhanced and a peak power conversion efficiency of 15.57% is obtained.