Innovative chiral molecule strategy boosts perovskite solar cell efficiency
by Simon Mansfield
Sydney, Australia (SPX) Jan 29, 2024
In the dynamic world of solar energy, metal halide perovskite solar cells (PSCs) have recently marked a significant milestone, with their power conversion efficiency (PCE) reaching an impressive 26.1%, inching closer to the efficiency levels of traditional crystalline silicon cells.
This achievement is particularly notable given the relatively short time span of just over a decade in which PSCs have developed. The latest research indicates that PSCs could potentially exceed a 30% PCE threshold, a development that could revolutionize solar energy technology.
The recent advancements in PSC technology primarily hinge on the quality of perovskite films used in these cells. The goal is to minimize defect density and achieve exceptional homogeneity in the films, thereby enhancing the overall performance of the solar devices.
Traditionally, the process of creating high-quality perovskite films involves introducing specific molecules during the film’s crystallization phase. These molecules help reduce defects or prevent excessive components in the films, a process known as passivation.
However, conventional passivation strategies in perovskite photovoltaics, typically involving the ABX3 structure, have their limitations. These limitations arise from the interactions between the passivation molecules and the perovskite sites, labeled as A, B, and X.
At the forefront of this research is Prof. Wang’s group from Soochow University, who have introduced a novel method for manipulating the crystal orientation of metal halide perovskites. Their approach involves using chiral molecules to establish a quantified strong force with formamidine (FA) ions in the perovskite, known as the magnetic dipole moment. This method addresses a critical issue in conventional perovskite film crystallization, where the production of a phase harmful to the device, termed the ‘d phase,’ is inevitable.
The use of chiral passivation molecules alone can regulate the composition of perovskite films but is insufficient to ensure an orderly overall structure. However, the application of an external magnetic field, leveraging the spin-orbit coupling effect, enhances this interaction. This allows for the precise adjustment of crystal orientation in the perovskite film while optimizing its composition.
Collaborating with Ilhan Yavuz and his team at Marmara University, Prof. Wang’s group has provided theoretical and computational support for this strategy. This collaboration has demonstrated the feasibility and effectiveness of this approach from both theoretical and experimental perspectives.
In contrast to conventional passivation strategies that involve the direct implementation of organic molecules, this new method significantly increases the interaction energy between chiral molecules and perovskites. This improvement ensures more effective crystallization regulation and achieves a uniform perovskite film.
The Shanghai Synchrotron Radiation Facility, with contributions from Xingyu Gao and colleagues, used in situ crystallization process detection technology to observe a clear and comprehensive improvement in the quality of perovskite films under this synergistic effect.