CsPbIBr2 has emerged as a highly promising material for optoelectronic applications, owing to its appropriately tuned bandgap and exceptional thermal stability. However, the practical fabrication of polycrystalline CsPbIBr2 thin films is severely constrained by the low solubility and poor stability of their precursor solutions. Here, we demonstrate a crown ether coordination strategy to enhance colloidal precursor reliability and elucidate the dissolution mechanism. We find that the soft-base characteristic of I– and the borderline base characteristic of Br– facilitate the formation of coordination complexes, PbXn2–n·DMSO (X = I/Br). The incorporation of 15-Crown-5 stabilizes the colloidal dispersion through interactions with Cs+ and Pb2+, thereby accelerating the dissolution of CsBr, increasing the ζ potential of colloids, and suppressing their aggregation and sedimentation. As a result, the obtained CsPbIBr2 films exhibit enhanced crystallinity, reduced defect density, and homogeneous charge distribution. The corresponding devices achieve a 50% increase of efficiency from 6.0 to 9.1% and demonstrate improved device stability under humid conditions. This work establishes a paradigm for integrating halide ion chemistry and crown ether coordination to overcome the limitations of precursor stability, thereby paving the way for high-performance CsPbIBr2-based optoelectronics.
Yang et al. (Fri,) studied this question.