Strategic Doping for Precise Structural Control and Intense Photocurrents under Visible Light in Ba2M0.4Bi1.6O6(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 Ba2M0.4Bi1.6O6 double perovskites. X-ray diffraction (XRD) and Rietveld refinement confirm crystallization in I2/m space group (M=La, Ce, Pr, Pb), and Fm3m and I2/m space groups (M=Y). The B1-O-B2 structure modulates to highly ordered (M=La, Y), partial 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-2 at 0.3 VRHE, 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-2 at 0.2 VRHE, outperforming all counterparts due to improved stability. Fine-tuning crystal and electronic structures by strategic B-sites doping, provides a new route for engineering Ba2Bi2O6-based double perovskites for broad solar energy conversion applications.