Ivan G. Scheblykin's team at Lund University published a research paper titled "In Operando Locally-Resolved Photophysics in Perovskite Solar Cells by Correlation Clustering Imaging" in the journal Advanced Materials. Boris Louis is the first author, and Sudipta Seth, Ivan G. Scheblykin, and Johan Hofkens are co-corresponding authors.
Key Highlight: This paper develops a non-invasive functional imaging method, correlation cluster imaging (CLIM), to demonstrate the presence of these fluctuations in both high-quality perovskites and their corresponding solar cells. CLIM successfully visualizes the polycrystalline grain structure in perovskite films, closely matching electron microscopy images. Fluctuation analysis reveals the primary metastable defects that cause these fluctuations. In solar cells under short-circuit conditions, these fluctuations are significantly enlarged, with the corresponding correlation region extending up to 10 microns, compared to a mere 2 microns in thin films.
The challenge of linking a material's structure to its functional properties is a cornerstone of materials science. Two-dimensional materials and various metal halide perovskites (MHPs) have a wide range of applications. Even in thin films and other large structures, MHPs exhibit detectable temporal variations in local photoluminescence (PL) resolved by optical microscopy. An intrinsic characteristic of MHPs is the presence of nanometer/micrometer-scale heterogeneity at grain and grain boundaries within perovskite films and devices, which impacts their performance and stability, highlighting the urgent need to connect their structure and function. Therefore, high-resolution functional imaging methods are in great demand for fundamental and applied research on contemporary electronic materials and devices.
In light of this, Sudipta Seth, Ivan G. Scheblykin, and Johan Hofkens of the Catholic University of Leuven at Lund University developed clustered correlation imaging (CLIM), a technique for detecting localized photoluminescence (PL) fluctuations using widefield fluorescence microscopy. Their research demonstrates that these fluctuations are present in both high-quality perovskites and their corresponding solar cells. CLIM successfully visualized the polycrystalline grain structure in perovskite films, closely matching electron microscopy images. Fluctuation analysis revealed the primary metastable defects responsible for these fluctuations. These fluctuations are significantly enlarged in solar cells under short-circuit conditions, with the corresponding correlation region extending up to 10 micrometers, compared to a mere 2 micrometers in thin films. This study suggests that the regions resolved by CLIM in solar cells harbor a common pool of charge extraction channels that fluctuate and contribute to PL variations. Because PL fluctuations reflect nonradiative recombination processes, CLIM provides valuable insights into the structural and functional dynamics of carrier transport, ion migration, defect behavior, and recombination losses. CLIM offers a non-invasive approach to understanding in-service light-emitting materials and devices based on previously underutilized properties.
This study anticipates that CLIM, with its novel imaging contrast, will become an important technique, enabling unique insights into microstructure-function relationships in dynamic materials and devices.
Source：https://doi.org/10.1002/adma.202413126