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

Abstract 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 EA 4 Pb 3 Cl 10 ( 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.