Hybrid Lead-Free Ferroelectric Solid Solutions with an Optimized Bandgap for X-ray Detection

Ferroelectric semiconductors hold promise for emerging applications in photovoltaics and photodetection. Solid ferroelectricity with a narrow bandgap has long been pursued to facilitate efficient charge generation and transport. However, their integration has been a continuous challenge as a possible leakage current can compromise ferroelectricity. Here, through the molecular modification and solid solution strategy on a series of one-dimensional (1,4-BDA)SbxBi1–xBr5 (x = 0–1) (BDA = 1,4-butanediaminium), we have achieved robust ferroelectricity with a high Curie temperature (Tc) of 379 K, and a reduced bandgap of 2.25 eV is realized in the composition (1,4-BDA)Sb0.7Bi0.3Br5. Benefiting from the promotion effect of the narrow bandgap and ferroelectric built-in electric field, compared to the parent (1,4-BDA)BiBr5, these attributes enable (1,4-BDA)Sb0.7Bi0.3Br5 to demonstrate X-ray detection capability with a sensitivity of up to 7479 μC Gyair–1 cm–2 and a limit of detection of 260 nGyair s–1, which is more than 21 times lower than that required for standard medical diagnostics. This study will provide insight into designing ferroelectric semiconductors for high-performance photoelectric devices.