Ionic Liquid-Assisted Crystallization Strategy Enables Simultaneous Regulation of Microstructure and Trap States for...

Area of Science:

• Materials Science
• Solid-state Chemistry
• Photovoltaics

Background:

• Antimony sulfoselenide (Sb2(S,Se)3) is a promising material for high-efficiency solar cells.
• Controlling its microstructure and electronic properties during crystallization is crucial but challenging.
• Defects and non-stoichiometry often limit device performance.

Purpose of the Study:

• To develop a feasible crystallization approach for Sb2(S,Se)3 absorbers.
• To simultaneously improve microstructure and reduce trap states using ionic liquids.
• To enhance the efficiency of Sb2(S,Se)3 solar cells.

Main Methods:

• Utilized ionic liquids (ILs) with halide anions (Cl-, Br-, I-) and [BMIM]+ cations to regulate Sb2(S,Se)3 crystallization.
• [BMIM]Br was employed to create a liquid microenvironment, accelerating mass transfer and promoting micron-size grain growth.
• Investigated the effect of ILs on film composition, defect transformation, and crystal orientation.

Main Results:

• [BMIM]Br induced micron-size grains and promoted [211]-oriented growth.
• Inhibited S and Se loss led to near-stoichiometric Sb2(S,Se)3 films with increased hole concentration and optimized band alignment.
• Transformed SbS antisite defects to VSe2 vacancy defects, significantly suppressing non-radiative recombination.

Conclusions:

• The [BMIM]Br-modulated Sb2(S,Se)3 solar cells achieved a record 10.89% efficiency and 72.74% fill factor.
• This strategy effectively addresses key challenges in Sb2(S,Se)3 solar cell development.
• The use of ILs offers a promising pathway for advancing Sb2(S,Se)3-based photovoltaics.