Organic-inorganic hybrid perovskites (OIHPs) with their exceptional optical and electrical properties and strong X-ray attenuation ability have gained considerable attention in direct X-ray detection. However, the challenge of suppressing ion migration for stable detection at high operating voltages still needs to be addressed.
The introduction of molecular electrostatic forces (i.e., halogen bonds) into compounds has been proven to further improve the intrinsic structural stability and inhibit ionic migration. However, this strategy has not been reported in the field of X-ray detection of bismuth halide perovskite (BHP).
In a study published in Advanced Science, Prof. LUO Junhua's group from the Fujian Institute of Research on the Structure of Matter of the Chinese Academy of Sciences realized stable X-ray detection by introducing multiple halogen interactions in lead-free perovskites.
The 0D BHPs (R/S-BPEA)4Bi2I10 (1, R/S-BPEA = R/S-1-(4-bromophenyl)ethylammonium) single crystals (SCs) with multiple intermolecular electrostatic forces were designed and synthesized. By introducing Br-substituted chiral organic cation BPEA, strong molecular interactions were created between the Br atom and the neighboring benzene ring (Br∙∙∙π), as well as with the I atoms on the inorganic perovskite framework (Br∙∙∙I), enhancing the activation energy for ion migration of 1, finally inhibiting ion migration.
As a result, X-ray detector based on high-quality SCs of 1 possessed a small dark current drift at a high working voltage, superior to many perovskite radiation detectors. Also, the detector exhibited a stable optical response even under continuous, prolonged X-ray irradiation of high dose rate and large external electric field.
Furthermore,1 crystallized in the chiral-polar space group of P21 induced by the organic chiral moiety. The intrinsic spontaneous electric polarization led to a strong bulk photovoltaic effect for driving the separation and transport of photogenerated carriers. The self-driven X-ray detection was achieved in the detector based on 1 SC with excellent performance.
This study exploits multiple interactions to synergistically achieve stable X-ray detection in lead-free polar semiconductors. It offers new possibilities for the development of portable and simple optoelectronic devices, and provides insights into the development of “green” self-powered high-stability X-ray detectors in the future.
Multiple interactions and excellent self-driven X-ray detection performance of lead-free polar perovskites. （Image by Prof. LUO’s group）
Contact:
Prof. LUO Junhua
Fujian Institute of Research on the Structure of Matter
Chinese Academy of Sciences
Email: jhluo@fjirsm.ac.cn
