Simple Ball‐Milled Molybdenum Sulfide Nanosheets for Effective Interface Passivation with Self‐Repairing Function to Attain High‐Performance Perovskite Solar Cells

Abstract

Interface defects can generate serious nonradiative recombination in perovskite solar cells (PSCs) and need to be restrained for further optimization of device performance. Herein, common and easily available 2D MoS2 nanosheets prepared by a ball‐milled method are demonstrated. The obtained MoS2 has bigger specific surface area and narrower pore distribution, inducing more water to be trapped on the surface or in pores of MoS2. With annealing, the locally absorbed water can be desorbed, and much more Mo atoms at the outermost surface layers could bond with oxygen to repair the uncoordinated Mo at edge sites for more ordered Mo—S—Mo bonds, which can weaken the catalytic activity of MoS2 to stabilize the heterojunction interface of hole transport layer (HTL)/perovskite. When it is used as the passivation layer between HTL and perovskite, the Mo2+–Mo4+ ion pair can promote electron transfer from Pb° to I°, suppressing the deep defects at this interface near the perovskite side. Meanwhile, MoS2 can passivate the surface (or grain boundaries) defects through the bond of Mo—I or Pb—O. The resultant PSCs give a champion efficiency of 22.39% with MoS2 treatment, thus enabling the decorated devices with excellent long‐term stability.

Bifunctional Interface Passivation via Copper Acetylacetonate for Efficient and Stable Perovskite Solar Cells

“…Fortunately, the discovery of a “redox shuttle” composed of an Eu 3+ –Eu 2+ metal ion pair has enabled successful electron transfer between Pb 0 and I 0 , resulting in the oxidation of Pb 0 to Pb 2+ and the reduction of I 0 to I – without consuming the Eu 3+ –Eu 2+ metal ion pair. Similarly, we have discovered that the Mo 2+ –Mo 4+ ion pair can effectively suppress the deep-level defects in the interface near the perovskite side via MoS 2 , leading to excellent device properties …”

“…Similarly, we have discovered that the Mo 2+ −Mo 4+ ion pair can effectively suppress the deep-level defects in the interface near the perovskite side via MoS 2 , leading to excellent device properties. 45 Copper acetylacetonate [Cu(acac) 2 ] molecule, with the monoclinic P2 1 /n space group, displays a planar structure and closes stacking along the crystallographic b axis, which facilitates the formation of a dominant one-dimensional supramolecular connectivity through π−π and Cu−π interactions, but the only weak dispersive interactions that propagated in other directions. 46,47 Due to the Schiff-base ligands, Cu(acac) 2 is often used as a cross-linking agent in photovoltaic devices.…”