Multi-Axial Broadband Photopyroelectric Response in Biaxial Perovskite Ferroelectric Crystals Driven by the Ferro-Pyro-Phototronic Effect

Broadband photopyroelectric photodetectors (PDs) based on single crystal (SC) show potential in near-infrared detection and imaging, attributed to their high crystalline properties, lack of grain boundaries, and bias-free. Nonetheless, the distinctive characteristic is attainable only with PDs crafted via the polar crystallographic axis direction. This constraint directly results in the reported SC-based photopyroelectric PDs being uniaxial, thus elevating the intricacy and expense in manufacturing devices. Herein, a multi-axis SC-driven broadband PD is realized, employing the ferro-pyro-phototronic (FPP) effect in a biaxial ferroelectric EA₄Pb₃Cl₁₀ (1, EA = ethylamine). In detail, the pyroelectric coefficients of 1 along the c- and b-axis are ≈ 2.6 × 10⁻³ and ≈ 3.5 × 10⁻³ µC cm⁻² K⁻¹, respectively, comparable to those of conventional pyroelectric materials like PVDF (≈ 2.7 × 10⁻³ µC cm⁻² K⁻¹). Importantly, this device surpasses its inherent optical bandgap to allow for a broad response from UV (UV, 266 nm) to near-infrared (NIR, 980 nm) wavelengths along both axes at zero bias. Such advancement signifies a major progress in the realm of SC-based multidirectional photopyroelectric detection, complete with broadband response.