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Mixed or Segregated: Toward Efficient and Stable Mixed Halide Perovskite-Based Devices
Hyejin Choe1, Dohyun Jeon2,3, Seon Joo Lee2
1Department of Chemistry, Duksung Women's University, Seoul 01369, South Korea.
ACS Omega
|October 4, 2021
Summary
Mixed halide perovskites offer tunable bandgaps for solar cells and LEDs but suffer from instability due to ion migration. This review explores halide segregation mechanisms and mitigation strategies for improved device longevity.
Area of Science:
- Materials Science
- Solid-State Physics
- Optoelectronics
Background:
- Mixed halide perovskites (MHPs) enable tunable bandgaps for perovskite solar cells (PSCs) and perovskite light-emitting diodes (PeLEDs).
- MHPs exhibit inherent instability under operational stress (light, electrical bias) due to their ionic lattice and high halide ion mobility.
- Halide ion migration, mediated by vacancies, and subsequent segregation are critical challenges impacting device performance and longevity.
Purpose of the Study:
- To review the intrinsic instability of MHPs stemming from their ionic nature and liquid crystalline properties.
- To elucidate the mechanistic models explaining photo- or electric field-driven halide ion segregation.
- To discuss strategies for mitigating halide segregation for enhanced device stability.
Main Methods:
- Review of existing literature on MHP instability and halide ion migration.
- Analysis of mechanistic models based on thermodynamics and kinetics of halide segregation.
- Discussion of composition-, defect-, dimension-, and interface-engineering approaches.
Main Results:
- Halide ion migration is facilitated by low formation energy of halide ion defects and liquid crystalline properties.
- Lattice strains and bandgap energy differences are identified as thermodynamic driving forces for halide segregation.
- Hole trapping and accumulation at iodide-rich sites are key to the segregation mechanism.
Conclusions:
- Understanding halide ion migration and segregation is crucial for improving MHP stability.
- Mitigation strategies involving material and device engineering can enhance long-term operational stability.
- This review provides insights for designing stable perovskite-based photovoltaic and optoelectronic devices.
