Controlling the Microstructure and Strain in Chiral 2D Perovskites by Additive Engineering

The growing demand for advanced data storage and signal processing technologies has intensified the search for novel materials with tunable optical and electronic properties. Chiral 2D perovskites have emerged as promising candidates due to their unique ability to selectively absorb and emit circularly polarized light, as well as to interact with polarizable currents. To exploit these properties in applications, chiral 2D perovskites should be integrated as thin films in various device architectures, yet the means to control their crystallization and film formation processes remain underdeveloped. This study demonstrates that additive engineering can be applied to control the microstructure and strain in chiral 2D perovskite thin films. It is shown that the addition of small amounts of hypophosphorous acid to the precursor solution of (R‐3BrPEA)2PbI4 chiral perovskites results in the dissolution of colloids, leading to a significant increase in the grain size and a release of lattice strain. Consequently, the intensity of their photoluminescence is significantly enhanced, demonstrating that grain boundaries and strain lead to nonradiative recombination losses in chiral 2D perovskites. The findings motivate the exploration of novel additive engineering approaches to improve the optoelectronic quality of chiral 2D perovskite thin films.