Perovskite solar cell defect management

Passivation of Defects in Perovskite-Based Solar Cells

Introduction to Solar Energy and Perovskite Solar Cells

The Promise of Solar Energy

Solar energy presents a  promising solution for reducing reliance on Fossil Fuels, offering a cleaner alternative. Over time, solar cell technology has advanced significantly in harnessing this renewable resource.

Metal-Halide Perovskites as Light-Absorbing Materials

Metal-Halide perovskites have attracted considerable interest as effective light-absorbing materials for solar cells, thanks to their outstanding optoelectronic properties that facilitate efficient energy generation from sunlight.

Challenges in Polycrystalline Perovskite Solar Cells

The Role of Polycrystalline Formamidinium Lead Iodide (FAPbl₃)

Poly-crystalline formamidinium lead iodide (FAPbl₃) is a favored material for constructing high-power conversion efficiency (PCE) perovskite solar cells (PSCs) due to its narrow energy band gap. However, despite its excellent optoelectronic properties and versatility, polycrystalline perovskites like FAPbl₃ often exhibit crystal structure defects that impair structural stability and carrier dynamics, ultimately reducing energy conversion efficiency.

Innovative Defect Passivation Strategy by GIST Researchers

Development of a Novel Defect Passivation Strategy

Filling this gap, a team of researchers headed by Professor Hobeom Kim at GIST has devised a novel defect pasivation strategy, which effectively reduces defects and boosts both power conversion efficiency and stability in perovskite solar cells.

In their recent Nature Commuinications study, dated July 4, 2024, the team introduced hexagonal polytype (6H) perovskite into cubic FAPbl₃ (3C),leading to a remarkable rise in PCE compared to existing counterparts.

The Advantages of 6H Perovskite Polytype

Why Choose 6H Perovskite?

Why opt for the 6H perovskite polytype? Prof. Kim explains, "The conventional method has been to introduce external chemical reagents to address defect issues. However, these reagents can negatively affect the crystalline integrity of perovskites during growth. Our approach avoids such stabilizers, instead utilizing the 6H polytype--a chemically identical version of perovskite with a corner-sharing structure that effectively prevents defect formation."

Incorporation and Impact of 6H Perovskite

By introducing excess lead iodide and methylammonium chloride, the researchers incorporated 6H perovskite into FAPbl₃, thereby addressing the key defect site, Halide Vacancies (VI+), present in the α-phase cubic polytype (3C) FAPbl₃.

Results and Implications

Future Prospects and Applications

The introduction of the 6H phase was found to bolster the structural stability and carrier dynamics of FAPbl₃, yielding an impressive carrier lifetime exceeding 18 microseconds. This improvement enabled PSCs to reach a PCE of 24.13%, with a module achieving a PCE of 21.92% (Certified at 21.44%) and demonstrating long-term operational durability.

According to the researchers, the 3C/6H Hetero-Polytypic perovskite design may closely approach the ideal structure for polycrystalline perovskite films. The study showcased how manipulating defects in perovskites can accelerate the development of cutting-edge solar cells for diverse uses such as rooftop installations, wearable electronics, and portable charging solutions.

Conclusion

The Transformative Potential of Perovskite Solar Cells

According to Prof. Kim, perovskite solar cells offer a trans-formative approach to reaching carbon neutrality and mitigating global warming. Their efficiency, adaptability, and reduced environmental impact make them integral to the transition towards sustainability.