We are pleased to announce that our new paper “Tailoring optical and ferroelectric properties in Sb₁₋ₓBiₓSI van der Waals chalcohalides towards solar absorber applications” has just been published in Journal of Materials Chemistry A.
In this work, we demonstrate that by substituting bismuth for antimony in SbSI — creating Sb₁₋ₓBiₓSI — we can continuously tune key properties relevant for photovoltaics. Specifically:
- The optical bandgap decreases rapidly at low Bi substitution levels and then stabilizes around 1.5 eV for higher Bi content
- At the same time, the ferroelectric character is gradually suppressed: soft-phonon modes vanish and second-harmonic generation (SHG) signals disappear, indicating the loss of ferroelectric order with Bi incorporation
- Our first-principles calculations support these observations, showing that Bi substitution weakens the lone-pair expression (on the Sb/Bi site), which destabilizes the ferroelectric ground state
This tunability of both structural and functional properties — bandgap and ferroelectric behavior — suggests that this system is a promising platform for next-generation solar absorbers: the 1.5 eV bandgap is well suited for photovoltaics, and the suppression of ferroelectricity provides insight into how electronic structure and structural distortions interplay in these van–der–Waals chalcohalides.
Congrats to Sara and all the co-authors and collaborators for their efforts!