Mitigating Band Tailing in Kesterite Solar Absorbers: Ab Initio Quantum Dynamics

Area of Science:

• Materials Science
• Solid-State Physics
• Renewable Energy

Background:

• Open-circuit voltage deficits limit kesterite solar cell performance.
• Suppressing band tailing and nonradiative recombination is crucial for efficiency.

Purpose of the Study:

• Elucidate the origin of band tailing and charge losses in kesterites.
• Propose a mitigation strategy for kesterite solar cells.

Main Methods:

• Ab initio nonadiabatic molecular dynamics simulations.
• Analysis of Urbach energy and band gap fluctuations.
• Investigating cation disorder effects.

Main Results:

• Cu-Zn disorder significantly increases band tailing and structural inhomogeneity.
• Cu-Zn disorder reduces band gap by 0.37 eV and increases fluctuations by 15 meV.
• Partial substitution of Zn with Cd suppresses band tailing and enhances charge carrier lifetimes.

Conclusions:

• Cation disorder is a primary cause of band tailing and reduced charge carrier lifetimes in kesterites.
• Cation disorder engineering, specifically Zn-Cd substitution, is a viable strategy for high-efficiency kesterite solar cells.