Solution-Processed Distributed Bragg Reflectors Using Lead Sulfide and Zinc Oxide Nanocrystal Thin Films

We report the fabrication and optical characterization of a fully solution-processed distributed Bragg reflector (DBR) comprising alternating thin films of lead sulfide (PbS) colloidal quantum dots (CQDs) and zinc oxide (ZnO) nanocrystals (NCs).The high refractive index of the PbS CQD film (> 3.0) and the low refractive index of the ZnO NC layer ( 1.5) enabled a substantial index contrast (n > 1.5), which is critical for achieving strong optical interference.By systematically correlating precursor concentration with film thickness, we demonstrated precise thickness control required for optical path engineering of a quarter wavelength.The designed DBRs exhibited high reflectivity and welldefined stopbands centered at 1,000 nm, exhibiting strong agreement between designed and measured optical responses.Our study highlights the potential of solution-processed NC-based DBRs and suggests that more uniform low-index colloidal materials can further enhance optical performance and scalability.