# Enhanced Stability and Performance of α-FAPbI3 Photodetectors via Long-Chain n-Heptanoic Acid Passivation

## TL;DR

Researchers improved the stability and performance of α-FAPbI3 photodetectors by using long-chain n-heptanoic acid to passivate crystal defects, resulting in high responsivity and long-term durability.

## Contribution

The use of long-chain n-heptanoic acid as a passivating agent significantly enhances the stability and performance of α-FAPbI3 photodetectors.

## Key findings

- n-Heptanoic acid passivation reduces defect states and inhibits non-radiative carrier recombination in α-FAPbI3 films.
- The optimized photodetector achieves a responsivity of 0.47 A W−1 at 740 nm.
- The device retains 95% of its initial performance after 552 hours in ambient conditions.

## Abstract

Owing to its narrow bandgap and excellent thermal stability, formamidinium–lead triiodide (FAPbI3) is a promising perovskite for high-performance, wide-spectrum photodetectors. Here, we selected long-chain n-heptanoic acid as the passivating agent and introduced it onto the perovskite surface via post-treatment, thereby enabling the fabrication of high-quality α-FAPbI3 perovskite films and photodetectors. It is found that the carboxylic acid group in the n-heptanoic acid molecule can effectively passivate crystal defects, greatly reduce the density of defect states in the perovskite film, and inhibit the non-radiative recombination of carriers. The α-FAPbI3 perovskite phase was effectively stabilized. The responsivity of the photodetector optimized by n-heptanoic acid is as high as 0.47 A W−1 at 740 nm. At the same time, the optimized device still maintains 95% of its initial performance after 552 h of storage in an air environment with a room temperature of 25 °C and a relative humidity of 25%. This method provides a reliable way to prepare a high-performance and stable α-FAPbI3 photodetector.