Band Structure Engineering of Cs₂AgBiBr₆ Perovskite through Order-Disordered Transition: A First-Principle Study

Area of Science:

• Materials Science
• Solid-State Physics
• Photovoltaics

Background:

• Methylammonium lead halides (CH₃NH₃PbI₃) are promising solar cell materials but face stability and toxicity issues.
• Cesium silver bismuth bromide (Cs₂AgBiBr₆) offers a stable, non-toxic alternative but has a wide indirect band gap limiting photovoltaic applications.

Purpose of the Study:

• To investigate the tunability of Cs₂AgBiBr₆ band gap through structural control.
• To explore methods for enhancing light absorption in Cs₂AgBiBr₆ for optoelectronic applications.

Main Methods:

• First-principle calculations were employed to model the electronic band structure.
• The effect of the ordering parameter on the band gap was systematically studied.

Main Results:

• The band gap of Cs₂AgBiBr₆ can be continuously tuned from 1.93 eV (ordered) to 0.44 eV (disordered) by controlling the ordering parameter.
• Growth temperature influences ordering parameters and band gaps, enabling control over light absorption.
• Controlled doping can further adjust the energy difference between ordered and disordered states, providing additional band gap control.

Conclusions:

• Band structure engineering in Cs₂AgBiBr₆ is achievable by manipulating the ordering parameter.
• This approach offers a novel strategy for optimizing mixed perovskites for optoelectronic devices, including solar cells.