# Coevaporated Formamidinium Tin Triiodide with Suppressed p‑Type Self-Doping

## TL;DR

A new method for making high-quality FASnI3 thin films without additives improves their stability and reduces defects.

## Contribution

A solvent-free coevaporation method that suppresses self-doping and oxidation in FASnI3 thin films.

## Key findings

- Coevaporated FASnI3 films have a bandgap of 1.31 eV, matching theoretical predictions.
- The method reduces Sn2+ oxidation and self-doping, leading to fewer defects.
- The process produces highly crystalline thin films without additives or reducing agents.

## Abstract

Coevaporation of
formamidinium tin triiodide (FASnI3) precursors, without
any additives or reducing agents, leads
to
the growth of a highly crystalline thin films which show a bandgap
around 1.31 eV, closely matching the theoretical value predicted from
the ideal single crystal structure of FASnI3. The polycrystalline
thin film presents a lower tendency toward Sn2+ to Sn4+ oxidation and highly reduced tendency toward self-doping,
demonstrating, overall, an improved resistance to defects formation.
These findings suggest solvent-free coevaporation processes as a promising
route for high quality Sn-based perovskite polycrystalline thin films.