The need for ferroelectric materials with both narrow bandgaps (Eg) and large remanent polarization (Pr) remains a key challenge to the development of high-efficiency ferroelectric photovoltaic (FPV) devices. In this work, [(K0.43Na0.57)0.94Li0.06][(Nb0.94Sb0.06)0.95Ta0.05]O3 (KNLNST)-based lead-free ceramics with narrow Eg and large Pr are obtained via Fe2O3 doping. By optimizing the level of Fe2O3 doping, a KNLNST+1.3% Fe2O3 ceramic is fabricated that simultaneously possesses a narrow Eg of 1.74 eV and a large Pr of 27.05 μC/cm2. These values are much superior to those of undoped KNLNST ceramics (Eg = 3.1 eV and Pr = 17.73 μC/cm2). While the large Pr stems from the increment of the volume ratio between the orthorhombic and tetragonal phases (VO/VT) in KNLNST ceramics by proper amount of Fe3+ doping, the narrow Eg is attributed to the coupling interaction between the Fe3+ dopants and the B-site Sb3+ host ions. Moreover, a switchable photovoltaic effect caused by the ferroelectric depolarization electric field (Edp) is observed in the KNLNST+1.3% Fe2O3 ceramic-based device. Thanks to the narrower Eg and larger Pr of the doped ceramic, the photovoltaic performance of the corresponding device (open-circuit voltage (Voc) = −5.28 V and short-circuit current density (Jsc) = 0.051 μA/cm2) under a downward poling state is significantly superior to that of an undoped KNLNST-based device (Voc = −0.46 V and Jsc = 0.039 μA/cm2). This work offers a feasible approach to developing ferroelectric materials with narrow bandgaps and large Pr for photovoltaic applications.
- Article type
- Year
- Co-author
![](/assets/img/article/article-lock.png)
![](/assets/img/article/article-lock.png)
AgNbO3 based antiferroelectric (AFE) ceramics have large maximum polarization and low remanent polarization, and thus are important candidates for fabricating dielectric capacitors. However, their energy storage performances have been still large difference with those of lead-based AFEs because of their room-temperature ferrielectric (FIE) behavior. In this study, novel La3+ and Ta5+ co-substituted AgNbO3 ceramics are designed and developed. The introduction of La3+ and Ta5+ decreases the tolerance factor, reduces the polarizability of B-site cations and increases local structure heterogeneity of AgNbO3, which enhance AFE phase stability and refine polarization-electric field (P–E) loops. Besides, adding La3+ and Ta5+ into AgNbO3 ceramics causes the decrease of the grain sizes and the increase of the band gap, which contribute to increased Eb. As a consequence, a high recoverable energy density of 6.79 J/cm3 and large efficiency of 82.1%, which exceed those of many recently reported AgNbO3 based ceramics in terms of overall energy storage properties, are obtained in (Ag0.88La0.04)(Nb0.96Ta0.04)O3 ceramics. Furthermore, the discharge properties of the ceramic with discharge time of 16 ns and power density of 145.03 MW/cm3 outperform those of many lead-free dielectric ceramics.