Quantifying exciton heterogeneities in mixed-phase organometal halide multiple quantum wells via Stark spectroscopy studies

Solution processable organic-inorganic hybrid perovskite (OIHP) quantum wells naturally self-assemble through weak van der Waals forces. In this study, we investigated the structural and optoelectronic properties of (C₄H₉NH₃)₂(CH₃NH₃)_n-1Pb_nI_3n+1, varying n from 1 to 4. Through conventional structural characterization, the thin films showcase high-quality phase purity. However, while investigating the optoelectronic properties, it was clear that these van der Waals heterostructures consist of multiple quantum well thicknesses coexisting within a single thin film. We utilized modulation spectroscopy, electroabsorption, and Liptay theory analysis to deconvolute the different excitonic features arising from different quantum well thicknesses (n). Rather than merely identifying what quantum well heterostructures are present within a thin film, this novel method of analysis provides powerful insight into the exact exciton composition in the thin film and can be utilized to analyze the optoelectronic properties of many other mixed-phase quantum well heterostructures beyond those formed by OIHPs.