Stoichiometric Dissolution of Defective CsPbI₂Br Surfaces for Inorganic Solar Cells with 17.5% Efficiency

Abstract

The existence of a defective area composed of nanocrystals and amorphous phases on a perovskite film inevitably causes nonradiative charge recombination and structural degradation in perovskite photovoltaics. In this study, a stoichiometric etching strategy for the top surface of a defective cesium lead halide perovskite is developed by using ionic liquids. The dissolution of the original defective area substantially exposes the underlying perovskite, which is a high‐quality surface with retained stoichiometry and lattice continuity. The ionic liquid molecules are adsorbed on the perovskite surface via Coulombic interactions and passivate the undercoordinated surface lead centers. Such a structural modulation considerably reduces the trap density of the perovskite devices and enables a record power conversion efficiency of 17.51% and an open‐circuit voltage of 1.37 V of the CsPbI2Br cell with a perovskite bandgap of 1.88 eV. This work provides a novel technical route to improve the efficiency and environmental resilience of perovskite‐based optoelectronic devices.

Polishing the Lead‐Poor Surface for Efficient Inverted CsPbI3 Perovskite Solar Cells

“…In this work, inspired by relationship between the carrier transport dynamics and the surface electronic states in the sem iconductors, [25][26][27][28][29][30] we focused on the surface components anal ysis of CsPbI 3 films and found that the intrinsically leadpoor surface was spontaneously formed with the stoichiometric pre cursors. Density functional theory (DFT) simulations concluded that the traps relevant to Pbpoor issues were p states, and the Pb vacancy (V Pb ) and I-Pb inversion (I Pb ) traps featured the localized states.…”

Defect‐Dependent Crystal Plane Control on Inorganic CsPbBr3 Film by Selectively Anchoring (Pseudo‐) Halide Anions for 1.650 V Voltage Perovskite Solar Cells

“…Considering ionic liquids have been widely used to passivate perovskites because of their versatile and unique properties including electrochemical and thermal stability, high ionic conductivity, and superior solubility, [41][42][43][44][45][46] we employed a series of popularly-used ionic liquids sharing identical 1-ethyl-3-methylimidazolium (EMIm) cations but with strategically varying anions (including NO 3 − , PF 6 − , BF 4…”

“…It is well known that organic cations in ionic liquid can interact with the perovskite lattice to passivate the ionic defects in the perovskite films and increase the hydrophobic ability of perovskite film. [44][45][46]49] As shown in Figure S7, Supporting Information, the shift of C-N stretching vibration peak of EMIm + toward the lower wavenumber after incorporation with PbBr 2 and CsBr suggests a weakened bond, demonstrating the interaction between EMIm + and the under-coordinated Pb 2+ and Cs + species in CsPbBr 3 lattice. However, it should be noted that the cations in four additives are the same, therefore, the anions play a more important role during crystallization.…”

Strain-free hybrid perovskite films based on a molecular buffer interface for efficient solar cells

“…Previous studies have proved that the defects at buried interface and grain boundaries are mainly shallower trap states. 45,46 Then, we investigated the effect of quaternary ammonium iodide molecules on the long-term stability of PSCs. As shown in Fig.…”