# The Effect of Component Defects on the Performance of Perovskite Devices and the Low-Cost Preparation of High-Purity PbI2

## TL;DR

This paper shows how impurities in PbI2 affect perovskite solar cell performance and introduces a low-cost method to produce high-purity PbI2.

## Contribution

A cost-effective method for synthesizing high-purity PbI2 with improved perovskite solar cell performance.

## Key findings

- Trace amounts of Pb(OH)I impurities hinder prenucleation cluster formation and degrade film morphology.
- High-purity PbI2 synthesized using the new method matches commercial PbI2 in photovoltaic performance.
- Strategies like pH adjustment and additive use effectively inhibit Pb(OH)I formation.

## Abstract

The efficiency and reproducibility of perovskite solar cells (PSCs) are significantly influenced by the purity of lead iodide (PbI2) in the raw materials used. Pb(OH)I has been identified as the primary impurity generated from PbI2 in water-based synthesis. Consequently, a comprehensive investigation into the impact of Pb(OH)I impurities on film and device performance is essential. In this study, PbI2, with varying stoichiometries, was synthesized to examine the effects of different Pb(OH)I levels on perovskite device performance. The characterization results revealed that even trace amounts of Pb(OH)I impede the formation of precursor prenucleation clusters. These impurities also increase the energy barrier of the α-phase and facilitate the transition of the intermediate phase to the δ-phase. These effects result in poor perovskite film morphology and sub-optimal photovoltaic device performance. To address these issues, a cost-effective method for preparing high-stoichiometry PbI2 was developed. The formation of Pb(OH)I was effectively inhibited through several strategies: adjusting solution pH and temperature, modifying material addition order, simplifying the precipitation–recrystallization process, and introducing H3PO2 as an additive. These modifications enabled the one-step synthesis of high-purity PbI2. PSCs prepared using this newly synthesized high-stoichiometry PbI2 demonstrated photovoltaic performance comparable to those fabricated with commercial PbI2 (purity ≥ 99.999%). Our novel method offers a cost-effective alternative for synthesizing high-stoichiometry PbI2, thereby providing a viable option for the production of high-performance PSCs.