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Tailoring Defects in Bismuth-Based Cs3Bi2Br9 Perovskite-Inspired Materials through Cooling-Rate Modulation for
Tanuj Kumar1, Mohit Kumar1, Ankush Saini1
1Advanced Research in Electrochemical Impedance Spectroscopy Laboratory, Indian Institute of Technology Roorkee, Roorkee, 247667, India.
Small (Weinheim an Der Bergstrasse, Germany)
|December 15, 2025
Summary
Controlled cooling of lead-free perovskite crystals minimizes defects, enhancing their electronic properties and stability. This advancement is crucial for developing efficient and safer semiconductor materials for future applications.
Area of Science:
- Materials Science
- Solid-State Physics
- Semiconductor Research
Background:
- Lead-based halide perovskites offer promising optoelectronic properties but suffer from toxicity and stability issues.
- Lead-free halide perovskites are emerging as safer alternatives, yet their properties are not fully understood.
- Defect formation significantly impacts the performance of semiconductor materials.
Purpose of the Study:
- To investigate the influence of cooling rate on defect formation in lead-free Cs3Bi2Br9 single crystals.
- To correlate crystal quality with photophysical and electronic properties.
- To assess the impact of defect reduction on photo-supercapacitor performance.
Main Methods:
- Synthesis of Cs3Bi2Br9 single crystals using controlled and natural cooling rates.
- High-resolution transmission electron microscopy (HRTEM) for defect analysis.
- Electrochemical impedance spectroscopy (EIS) to measure grain resistivity.
- Contact angle measurements for surface hydrophobicity assessment.
- Fabrication and testing of monolithic photo-supercapacitors.
Main Results:
- Controlled cooling significantly reduced trap density and eliminated point defects and dislocations in Cs3Bi2Br9 crystals.
- Naturally cooled crystals exhibited defects, leading to a tenfold increase in grain resistivity.
- Controlled-cooled perovskite films showed enhanced surface hydrophobicity, indicating improved stability.
- Photo-supercapacitors using controlled-cooled perovskites demonstrated over 130% photo-capacitance enhancement, compared to 40% for naturally cooled ones.
Conclusions:
- The cooling rate is a critical factor in controlling defect formation in lead-free perovskite crystals.
- Minimizing defects through controlled cooling enhances electronic properties, stability, and device performance.
- This study provides a pathway for optimizing lead-free perovskites for advanced optoelectronic applications.
