# Strategic Doping for Precise Structural Control and Intense Photocurrents Under Visible Light in Ba2M0.4Bi1.6O6 (M = La, Ce, Pr, Pb, Y) Double Perovskites

## TL;DR

This study explores how doping affects the structure and performance of Ba2M0.4Bi1.6O6 perovskites for solar energy conversion.

## Contribution

Strategic B-site doping is shown to enable precise structural control and enhance photocurrents under visible light in double perovskites.

## Key findings

- Doping with La and Y leads to highly ordered structures and strong light absorption with band gaps of ~1.57 eV and ~1.73 eV.
- La-doped photoelectrodes generate 1 mA cm−2 photocurrents under AM 1.5G illumination, outperforming Ce and Pb counterparts.
- Increasing La-doped photoelectrode thickness to 7.7 μm boosts photocurrents to 2.3 mA cm−2 due to improved stability.

## Abstract

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 the I2/m space group (M = La, Ce, Pr, Pb), and Fm
3¯m and I2/m 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−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 via strategic B-site doping provides a new route for engineering Ba2Bi2O6-based double perovskites for broad solar energy conversion applications.