Optimizing Crystallization in Wide-Bandgap Mixed Halide Perovskites for High-Efficiency Solar Cells

Area of Science:

• Materials Science
• Renewable Energy
• Photovoltaics

Background:

• Wide-bandgap (WBG) perovskites are crucial for top subcells in tandem solar cells (TSCs) due to tunable bandgaps.
• Challenges include inhomogeneous crystallization, nonradiative recombination, high open-circuit voltage (V_OC) deficits, and poor stability in WBG perovskites.

Purpose of the Study:

• To develop efficient and stable WBG perovskite solar cells (PSCs) by addressing crystallization and defect issues.
• To introduce a multifunctional additive for improved perovskite film quality and performance.

Main Methods:

• A phenylethylammonium acetate (PEAAc) additive was used to regulate mixed-halide crystallization, promoting uniform halide phase distribution and reducing defect density.
• The strategy was applied to FAMACsPb(I_1-xBr_x)₃ perovskite systems with varying bandgaps (1.73–1.92 eV).
• WBG perovskites were integrated with organic photovoltaics to create two-terminal TSCs.

Main Results:

• Efficient WBG PSCs with reduced V_OC loss and enhanced stability were achieved.
• Power conversion efficiencies (PCEs) of 21.3% (1.73 eV), 19.5% (1.79 eV), 18.1% (1.85 eV), and 16.2% (1.92 eV) were obtained for WBG PSCs.
• A record V_OC of ≈ 2.2 V and PCE over 24% were achieved for two-terminal perovskite/organic TSCs.

Conclusions:

• The PEAAc additive effectively addresses phase separation and inhomogeneous crystallization in Br-rich perovskite films.
• This approach enables the development of high-performance WBG PSCs and TSCs.
• The findings pave the way for advancing perovskite-based solar cell technologies.