Fig. 1: High-throughput material composition exploration with combinatorial printing.

a Schematic of the high-throughput workflow has three stages: depositing the material with a linear composition gradient on the substrate, annealing the substrate to facilitate crystallization, and characterizing the optical properties. b High-throughput optical characterization of gradient-printed samples from Cs₃Bi₂I₉ (upper left, 0D dimer structure) to Cs₃Bi₂Br₉ (bottom right, 2D layered structure). c Spatially resolved bandgap maps of one droplet sample. d The corresponding Tauc plots and fitting results of individual pixels in c. “a.u.” denotes “arbitrary units”. e Extracted reflectance spectra from the sequence (Cs₃Bi₂Br₉)_x(Cs₃Bi₂I₉)_1-x. “a.u.” denotes “arbitrary units”. f Bandgap extraction of six halide perovskite composition gradients through hyperspectral optical imaging.