Pb dimerization greatly accelerates charge losses in MAPbI3: Time-domain ab initio analysis.
Zhaosheng Zhang1, Lu Qiao1, Carlos Mora-Perez2
1College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education, Beijing Normal University, Beijing 100875, People's Republic of China.
The Journal of Chemical Physics
|February 17, 2020
Summary
Defects in metal halide perovskites significantly impact performance. A lead dimer defect dramatically accelerates charge losses, unlike a simple lead interstitial, offering insights for improving perovskite devices.
Area of Science:
- Materials Science
- Solid-State Physics
- Computational Chemistry
Background:
- Metal halide perovskites are promising semiconductors for solar cells due to efficient light harvesting and long charge carrier lifetimes.
- Device performance is often limited by nonradiative charge and energy losses, which are exacerbated by material defects.
Purpose of the Study:
- To investigate the influence of defect chemical states on charge losses in metal halide perovskites.
- To atomistically analyze the impact of an extra lead (Pb) atom defect in methylammonium lead iodide (CH3NH3PbI3) on charge trapping and recombination.
Main Methods:
- Employed nonadiabatic molecular dynamics combined with time-domain density functional theory.
- Simulated charge trapping and recombination dynamics for different chemical states of excess Pb atoms.
Main Results:
- A Pb interstitial defect showed a mild effect on charge recombination.
- A Pb dimer defect significantly accelerated charge trapping and recombination by creating a midgap trap state.
- Hole decay from the valence band and recombination with conduction band electrons were orders of magnitude faster in the presence of a Pb dimer.
Conclusions:
- The chemical state of defects critically influences charge loss mechanisms in perovskites.
- Pb dimer defects act as efficient recombination centers, detrimental to perovskite performance.
- Understanding these atomistic defect dynamics provides crucial theoretical guidance for enhancing perovskite solar cell efficiency.
