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Identifying and Passivating Killer Defects in Pb-Free Double Cs2AgBiBr6 Perovskite
Yalan She1, Zhufeng Hou2, Oleg V Prezhdo3
1School of Chemistry and Materials Science, Hunan Agricultural University, Changsha 410128, China.
The Journal of Physical Chemistry Letters
|October 25, 2021
Summary
Lead-free double perovskites show promise for solar cells but suffer from defects. Doping with indium mitigates detrimental bromine vacancies, significantly improving optoelectronic performance and paving the way for efficient devices.
Area of Science:
- Materials Science
- Solid-State Physics
- Photovoltaics
Background:
- Lead-free double perovskites like Cs2AgBiBr6 offer stable, non-toxic alternatives to lead halide perovskites for solar cells.
- Despite advantages, their photovoltaic performance remains limited.
Purpose of the Study:
- To investigate the atomistic origins of performance limitations in Cs2AgBiBr6.
- To propose a defect mitigation strategy for enhancing optoelectronic properties.
Main Methods:
- Combined nonadiabatic molecular dynamics (NAMD) and real-time time-dependent density-functional theory (RT-TDDFT).
- Simulated defect behavior and electronic structure in Cs2AgBiBr6.
Main Results:
- Identified a detrimental donor-yielded (DY) center associated with a negatively charged bromine vacancy.
- Observed hole trapping within picoseconds due to Ag+-Bi3+ bonding around the vacancy.
- Indium doping weakened the In-Bi bond, shifting the defect level and reducing hole trapping by an order of magnitude.
- Trap-assisted charge recombination decreased four-fold with indium doping.
Conclusions:
- Atomistic insights into defect mechanisms in lead-free double perovskites were gained.
- Indium doping presents a viable strategy for defect mitigation and performance enhancement in Cs2AgBiBr6 optoelectronic devices.
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