Strong Electron Localization in Tin Halide Perovskites.

Area of Science:

• Materials Science
• Solid-State Physics
• Computational Chemistry

Background:

• Tin halide perovskites (THPs) are emerging as promising low-toxicity alternatives to lead halide perovskites.
• Understanding the behavior of photoexcited charge carriers is crucial for THP applications but remains poorly understood.
• Investigating electron dynamics is key to unlocking the potential of these materials.

Purpose of the Study:

• To elucidate the behavior of excess electrons in a series of tin halide perovskites.
• To determine the preferred states of self-trapped electrons in THPs.
• To assess the prevalence of electron localization across different THP compositions.

Main Methods:

• Advanced electronic-structure calculations were employed.
• Density Functional Theory (DFT) was utilized to model electron behavior.
• Calculations focused on CsSnBr3 and extended to other compositions like CsSnI3, CsSnCl3, MASnBr3, FASnBr3, and DMASnBr3.

Main Results:

• Electron localization is energetically favorable in CsSnBr3.
• Bipolaronic states represent the most stable form of self-trapped electrons in CsSnBr3.
• Stable electron bipolarons were consistently observed across all investigated tin halide perovskites, including CsSnI3, CsSnCl3, MASnBr3, FASnBr3, and DMASnBr3.

Conclusions:

• Strong electron localization is a recurrent characteristic of tin halide perovskites.
• The formation of stable electron bipolarons is a common phenomenon in THPs.
• These findings provide fundamental insights into charge carrier dynamics in low-toxicity perovskites.