Researchers from the Netherlands and the United Kingdom have published a study that sheds light on the nanoscale optical properties of halide perovskite semiconductors, which are promising materials for high-efficiency solar cells. The team, led by Robin Schot and Saskia Fiedler from the Center for Nanophotonics at AMOLF in Amsterdam, and including collaborators from the University of Cambridge, has investigated the variations in optical properties within and between crystallographic grains of these materials.
Halide perovskite semiconductors are known for their excellent light-harvesting capabilities, making them a hot topic in the solar energy sector. However, their efficiency can be hampered by losses at the nanoscale, particularly at the boundaries between crystallographic grains. To understand these losses, the researchers used a technique called spatially-resolved cathodoluminescence (CL) spectroscopy. This method allows them to map the light emission properties of the material at high resolution.
The CL maps revealed a significant reduction in light emission intensity near the grain boundaries. To understand why this happens, the team performed numerical simulations using surface profiles obtained from atomic force microscopy (AFM). They found that the curved surfaces near the grain boundaries enhance internal reflection and light trapping, reducing the amount of light that can escape the material. Additionally, they observed variations in CL intensity within the grains, which they attributed to Fabry-Perot-like resonances in the film, with the substrate acting as a back reflector.
The study highlights the importance of near-field coupling and interference effects in the optical properties of halide perovskite films. These findings are not only relevant for the analysis of cathodoluminescence and photoluminescence of corrugated thin films but also have practical implications for the energy sector. By understanding and mitigating these nanoscale losses, researchers can potentially improve the efficiency of perovskite solar cells, bringing us one step closer to more efficient and affordable solar energy solutions.
The research was published in the journal Nature Communications.
This article is based on research available at arXiv.