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Band Gap Narrowing in Lead-Halide Perovskites by Dynamic Defect Self-Doping for Enhanced Light Absorption and Energy
Yongliang Shi1,2, Weibin Chu3,4, Lili Zhang5
1State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China.
Chemistry of Materials : a Publication of the American Chemical Society
|February 3, 2025
Summary
Dynamic defects in all-inorganic metal halide perovskites (MHPs) enhance solar energy capture by narrowing the band gap. This defect behavior optimizes MHPs for efficient solar cells and optoelectronics.
Area of Science:
- Materials Science
- Solid State Physics
- Photovoltaics
Background:
- Metal halide perovskites (MHPs) show promise for photovoltaics with efficiencies exceeding 25%.
- Hybrid organic-inorganic MHPs suffer from chemical instability.
- All-inorganic MHPs like CsPbI3 have lower stable efficiencies (~18%) due to wider band gaps.
Purpose of the Study:
- To introduce a new concept of dynamic defects in metal halide perovskites.
- To investigate how these dynamic defects impact light absorption and charge carrier recombination.
- To explore defect covalency and dynamics for optimizing MHPs in solar energy applications.
Main Methods:
- Utilized α-CsPbI3 as a model system for studying dynamic defects.
- Investigated defect states fluctuating between deep and shallow energy levels.
- Analyzed the role of defect covalency and low-frequency anharmonic vibrations.
Main Results:
- Demonstrated dynamic defects that increase absorbed solar photon range without accelerating recombination.
- Observed defects narrowing the band gap in deeper states for longer wavelength absorption.
- Showcased defect-mediated upconversion of thermal energy into electricity via charge escape in shallower states.
Conclusions:
- Defect dynamics and defect covalency are crucial properties of MHPs.
- Dynamic defects can enhance light harvesting and charge transport in MHPs.
- This approach offers a pathway to optimize MHPs for efficient solar energy conversion and optoelectronics.
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