Strategic Doping for Precise Structural Control and Intense Photocurrents Under Visible Light in BaMBiO (M = La, Ce, Pr, Pb, Y) Double Perovskites.

Developing functional perovskites is important for advancing solar energy conversion technologies. This study investigates the effects of dopants on the structural, optical, electronic, and solar conversion performances of BaMBiO double perovskites. X-ray diffraction (XRD) and Rietveld refinement confirm crystallization in the 2 space group (M = La, Ce, Pr, Pb), and 3¯ and 2 space groups (M = Y). The B1-O-B2 structure modulates to highly ordered (M = La, Y), partially ordered (M = Pr), or disordered (M = Ce, Pb). UV-vis spectra show strong light absorption, with Tauc plots estimating ~1.57 eV (M = La) and ~1.73 eV (M = Pr) optical band gaps. Under AM 1.5G illumination, the M = La photoelectrode generates photocurrents of 1 mA cm at 0.3 V, surpassing M = Ce and Pb (1 μm, 4-times spin-coating). Increasing its thickness to 7.7 μm (4-times dip-coating) further enhances the photocurrents to 2.3 mA cm at 0.2 V, outperforming all counterparts due to improved stability. Fine-tuning crystal and electronic structures via strategic B-site doping provides a new route for engineering BaBiO-based double perovskites for broad solar energy conversion applications.