Self‐Poled Halide Perovskite Ruddlesden‐Popper Ferroelectric‐Photovoltaic Semiconductor Thin Films and Their Energy Harvesting Properties

Abstract Ambient energy harvesters with multi‐source energy harvesting capabilities are highly desirable for developing compact and sustainable power solutions for emerging technologies such as the Internet of Things. In this study, thin films of low‐dimensional halide perovskites, (BA) 2 (MA) n‐1 Pb n Br 3n+1 ( n = 1, 2), are demonstrated to be both semiconducting and ferroelectric, enabling the harvesting of mechanical and ambient light energy. By incorporating Cr/Cr₂O₃ or phenyl‐C 61 ‐butyric acid methyl ester (PCBM) as a barrier/passivation layer, reproducible ferroelectric properties are consistently achieved in (BA) 2 (MA) n‐1 Pb n Br 3n+1 ₊₁ thin films. The corresponding flexible piezoelectric energy harvesters delivered a peak‐to‐peak open‐circuit voltage of 8 V under a 10 N force, while the photovoltaic devices exhibited an open‐circuit voltage of ≈1.2 V under 1 Sun illumination. This study unveils the potential of low‐dimensional halide perovskite thin films for lightweight, multi‐source energy harvesting and provides key insights into the crucial role of barrier layers in achieving reliable thin‐film halide perovskite ferroelectric devices.