# Nanocrystal Synthesis Derived Approach to Silver Bismuth Iodide Layered Double Perovskites with Aliphatic Amines: (C n H(2n+1)NH3)4AgBiI8

## TL;DR

This paper presents a new method to synthesize stable, lead-free silver bismuth iodide perovskites using aliphatic amines, which could be useful for low-toxicity optoelectronic applications.

## Contribution

A fast precipitation method for synthesizing layered iodide double perovskites with improved structural stability.

## Key findings

- The synthesized compounds have a monoclinic crystal structure with alternating [AgI6] and [BiI6] octahedra.
- The materials exhibit a band gap of 2.1 eV, confirmed by both experimental and theoretical methods.
- Phase transitions are similar to those of lead-based perovskites, indicating structural similarities.

## Abstract

Lead-free iodide double perovskites are an interesting
class of
materials since they combine a relatively low toxicity (compared to
the lead counterpart) with the small band gap typical of iodide-based
perovskite structures. Their reported number is small due to their
lower structural stability compared to the chloride and bromide analogues;
hence, their synthesis is difficult. The structural constraints that
limit stability, on the other hand, can be much relieved in layered
organic–inorganic perovskites. Following this line of thought,
we report here a successful fast precipitation route to iodide layered
(C
n
H(2n+1)NH3)4AgBiI8 (n =
10, 12, and 14) double perovskites that borrow concepts from the synthesis
of colloidal nanocrystals. X-ray diffraction studies revealed for
these compounds a monoclinic crystal structure containing edge-sharing-alternating
[AgI6] and [BiI6] octahedra. These materials
have experimental band gaps of 2.1 eV, as also corroborated by theoretical
calculations. We have also investigated their phase transitions by
thermal analysis and temperature-dependent diffraction and found them
to be similar to their lead-based layered perovskite counterparts.