# Origin of High Efficiency and Long-Term Stability in Ionic Liquid Perovskite Photovoltaic

## TL;DR

This paper explains how ionic liquids improve the efficiency and stability of perovskite solar cells by acting as solvents, additives, and passivators.

## Contribution

The study reveals the multifunctional role of protic amine carboxylic acid ionic liquids in perovskite solar cells.

## Key findings

- Ionic liquids dissolve perovskite precursors, induce oriented crystallization, and passivate grain boundaries.
- The unique molecular structure of ionic liquids allows strong interactions with perovskite materials.
- This approach is applicable to a wide range of IL-based perovskite optoelectronics.

## Abstract

Environment-friendly protic amine carboxylic acid ionic liquids (ILs) as solvents is a significant breakthrough with respect to traditional highly coordinating and toxic solvents in achieving efficient and stable perovskite solar cells (PSCs) with a simple one-step air processing and without an antisolvent treatment approach. However, it remains mysterious for the improved efficiency and stability of PSCs without any passivation strategy. Here, we unambiguously demonstrate that the three functions of solvents, additive, and passivation are present for protic amine carboxylic acid ILs. We found that the ILs have the capability to dissolve a series of perovskite precursors, induce oriented crystallization, and chemically passivate the grain boundaries. This is attributed to the unique molecular structure of ILs with carbonyl and amine groups, allowing for strong interaction with perovskite precursors by forming C=O…Pb chelate bonds and N-H…I hydrogen bonds in both solution and film. This finding is generic in nature with extension to a wide range of IL-based perovskite optoelectronics.