Halide Double Perovskites Cs₂PdBr_6-I with Tunable Bandgaps for Solar Cells

Area of Science:

• Materials Science
• Solid State Physics
• Renewable Energy

Background:

• Lead-based perovskites face toxicity and stability challenges.
• Inorganic lead-free vacancy-ordered double perovskites (A2BX6) are explored as alternatives.
• Mixed-halide compositions offer tunable properties.

Purpose of the Study:

• To design and investigate mixed-halide Cs2PdBr6-xIx double perovskites.
• To evaluate their structural, electronic, and photoelectric properties.
• To assess their potential for single-junction and tandem solar cells.

Main Methods:

• Density Functional Theory (DFT) calculations were employed.
• Formation energy was calculated to assess thermodynamic stability.
• Electronic band structures and optical absorption spectra were analyzed.

Main Results:

• Cs2PdBr6-xIx perovskites demonstrate thermodynamic stability with negative formation energies.
• Tunable direct or quasi-direct bandgaps range from 0.77 to 1.73 eV.
• Significant expansion of visible light absorption and high theoretical spectral limit maximum efficiency (SLME) up to 32% were achieved.

Conclusions:

• Mixed-halide Cs2PdBr6-xIx double perovskites are promising lead-free alternatives for solar cells.
• Their tunable bandgaps and high efficiency make them suitable for single-junction applications.
• Specific compositions can be utilized as bottom or top cells in tandem solar cell configurations.