Using Microspectroscopy in the Study of Perovskite Materials
Clean energy could be verging on a revolution. In recent years, mainstream solar companies have invested increasingly significant sums in commissioning new pilot production lines. The goal is to realize commercial-scale manufacturing of novel perovskite solar cells.
Greater adoption of perovskites in the industry buoys hopes for perovskite-silicon tandem cells or multi-junction photovoltaics, which could introduce unprecedented efficiencies beyond the theoretical limit of 33.7%. However, ongoing study is needed to conduct nanoscale characterization, correlate structural and chemical information with local properties, uncover degradation mechanics, and more. UV-visible-NIR microspectrophotometry is invaluable in this arena.
An Introduction to Perovskites
Perovskite is a calcium titanium oxide (CaTiO₃) mineral. Its distinctive crystal structure is described by the formula ABX₃, where 'A' and 'B' are cations of different sizes, and 'X' is an anion that bonds to both. This structure offers enormous compositional versatility, enabling tunable optoelectronic properties. Crucially for the solar industry, perovskite materials offer efficient charge transport and strong light absorption. Single-junction perovskite solar cells have achieved power efficiencies exceeding 25%, while lab efficiencies have approached the Shockley-Queisser limit. These exciting developments dovetail with the fact that perovskite materials also support tunable bandgaps for optimizing specific wavelengths and exhibit high defect tolerance, simplifying fabrication and reducing costs.
Realising this enormous potential requires thorough material characterization and robust in-line quality assurance and control. Naturally, many tools are used to accomplish these goals. But microspectrophotometry is a standout. It offers a unique capability to analyze perovskite materials at microscopic levels, providing valuable insights into their optical properties, spatial variations, degradation mechanisms, thin film thickness, and more.
Characterizing Optical Properties
Microspectroscopy is ideal for characterizing the optical properties of perovskite materials. This technique enables researchers to measure the absorption, transmission, reflection, and emission spectra of perovskite thin films and nanocrystals at a microscopic scale. Understanding these optical properties is crucial for optimizing the performance of perovskite-based optoelectronic devices. For instance, the absorption spectrum provides information about the bandgap and electronic transitions, which are vital for improving the efficiency of perovskite solar cells. Similarly, emission spectra are essential for developing high-performance perovskite-based light-emitting diodes (LEDs).
Mapping Spatial Variations
A significant advantage of microspectroscopy is its ability to map spectral characteristics with micron-scale spatial resolution. This capability is particularly important for investigating spatial variations in the composition, crystallinity, and defects within perovskite materials. Spatial heterogeneities can profoundly impact the optoelectronic properties of perovskites, influencing their performance in devices. For example, variations in composition can lead to inhomogeneous light absorption and emission, while differences in crystallinity can affect charge transport properties. By mapping these variations, researchers can identify and mitigate defects, leading to the development of more efficient and reliable perovskite-based devices.
Analyzing Degradation and Stability
Perovskite materials are known for their sensitivity to environmental factors such as moisture, oxygen, and heat, which can lead to degradation and instability. Microspectroscopy is critical in monitoring changes in the optical properties of perovskite materials under different environmental conditions. By examining how these properties evolve, researchers can gain insights into the degradation mechanisms and devise strategies to enhance the stability of perovskite materials. For example, monitoring the absorption spectrum over time can reveal the formation of degradation products, while changes in emission spectra can indicate the loss of luminescence efficiency due to environmental stress.
Thin Film Thickness Measurements
Accurate measurement of thin film thickness is essential for optimizing the performance of perovskite-based devices, as film thickness significantly influences the material's optical and electronic properties. Microspectroscopy allows precise measurement of perovskite thin film thickness by analyzing the interference patterns in the spectra. This information is critical for designing devices with optimal layer thicknesses to achieve the best performance. For instance, in solar cells, the thickness of the perovskite layer must be optimized to maximize light absorption while ensuring efficient charge transport.
In-Situ and Operando Studies
Combining microspectroscopy with other techniques, such as environmental chambers or electrochemical cells, enables in-situ and operando studies of perovskite materials. These studies are essential for understanding the dynamic processes occurring in perovskite materials during device operation or under different environmental conditions. For example, in-situ microspectroscopy can be used to monitor the evolution of optical properties during the fabrication of perovskite solar cells, providing real-time feedback for process optimization. Operando studies, on the other hand, allow researchers to observe changes in the material's properties while the device operates, offering insights into performance and stability under real-world conditions.
Interested in Microspectrophotometry?
Microspectroscopy, particularly UV-Visible-NIR microspectrophotometry, is a powerful and versatile tool for studying perovskite materials. It provides detailed insights into the optical properties, spatial variations, degradation mechanisms, and film thickness of perovskites, all crucial for advancing the development of high-performance optoelectronic devices. By leveraging the capabilities of microspectroscopy, researchers can address the challenges associated with perovskite materials and unlock their full potential in various technological applications.
References & Further Reading
- Ford, Neil. Perovskite solar goes commercial as yield gains align with market forces. Reuters. 2023. [Available at: https://www.reuters.com/business/energy/perovskite-solar-goes-commercial-yield-gains-align-with-market-forces-2023-02-02/]
- Bhattacharya, S., John, S. Beyond 30% Conversion Efficiency in Silicon Solar Cells: A Numerical Demonstration. Sci Rep 9, 12482 (2019). https://doi.org/10.1038/s41598-019-48981-w
