Ferroelectric
(FE) materials are thought to be promising materials for self-powered
ultraviolet (UV) photodetector applications because of their photovoltaic
effects. However, FE-based photodetectors exhibited poor performance
because of the weak photovoltaic effect of FE depolarization field
(E
dp) on the separation of photo-generated
carriers. In this work, self-powered photodetectors based on both E
dp and built-in electric field at the p-n junction
(E
p‑n) were designed to obtain
enhanced device performance. A NiO/Pb0.95La0.05Zr0.54Ti0.46O3 (PLZT) heterojunction-based
device is constructed to take advantage of energy level alignments
that favor electron extraction. The device exhibits a tunable performance
upon varying the polarization direction of PLZT. The NiO/PLZT heterojunction-based
device with the PLZT layer in the poling down state shows a higher
responsivity [R = (1.8 ± 0.12) × 10–4 A/W] and detectivity [D* = (3.69
± 0.2) × 109 Jones], a faster response speed
(τr = 0.34 ± 0.03 s, τd = 0.36
± 0.02 s), and a lower dark current [I
dark = (1.3 ± 0.19) × 10–12 A] under zero
bias than the PLZT-based device because of the synergistic effects
of E
dp and E
p‑n. Moreover, under weak-light illumination (0.1 mW/cm2),
it exhibits even higher R [(6.3 ± 1.2) ×
10–4 A/W] and D* [(1.29 ±
0.26) × 1010 Jones] values, which surpass those of
most previously reported FE-based self-powered photodetectors. Our
work emphasizes the role of the coupling effect between E
p‑n and E
dp in the
photovoltaic process of NiO/PLZT heterojunction-based devices and
provides an effective way to promote the self-powered UV photodetector
applications.
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