Anisotropic X-ray photovoltaics in 2D trilayered hybrid perovskite EA4Pb3Br10 single crystals with a low detection limit

Abstract

Two-dimensional (2D) hybrid perovskite ferroelectrics, characterized by a highly tunable structure and intrinsic structural anisotropy, have emerged as promising materials for photodetection and X-ray detection, thanks to their outstanding photoelectric properties. Despite recent blooming advances, the relationship between the structure and properties of 2D perovskite ferroelectrics remains unclear. In this study, we conducted a comprehensive analysis of the photoelectric properties along the crystallographic axes of the 2D perovskite ferroelectric EA₄Pb₃Br₁₀ (EA = ethylammonium), achieving successful X-ray detection at zero bias through bulk photovoltaic effects (BPVEs). The EA₄Pb₃Br₁₀ single crystals (SCs) exhibited notable anisotropic behaviors in dielectric properties, conductivity and carrier transport. Significant piezoelectric responses of 3 and 6 pC N⁻¹ were measured along the a- and c-axes, respectively, confirming the material's polar nature. Photodetectors fabricated from poled EA₄Pb₃Br₁₀ SCs showcased pronounced anisotropic BPVEs, with an open-circuited photovoltage of approximately 0.5 V along the a- and c-axes and an ultrafast response time of about 20/120 ns. The temperature-dependent photovoltaic currents of EA₄Pb₃Br₁₀ indicated that BPVEs are initially linked to their ferroelectricity. Leveraging the superior BPVEs and anisotropic properties, EA₄Pb₃Br₁₀ SCs demonstrated distinctive anisotropic X-ray responses, achieving a high sensitivity of 1251 μC Gy_air⁻¹ cm⁻² and a low detection limit of 56 nGy_air s⁻¹ at 0 V bias. This study not only elucidates the anisotropic structure–property relationship of 2D perovskite ferroelectrics, but also underscores their significant potential in self-powered X-ray detection applications.