Polarization-Induced Photovoltaic Effects in Nd-Doped BiFeO₃ Ferroelectric Thin Films

Abstract

Nd-doped BiFeO 3 (BNF) thin films were fabricated on SrRuO 3 (SRO)-coated (100) Nb-doped SrTiO 3 substrates by pulsed laser deposition, and nondoped BiFeO 3 (BFO) thin films were also fabricated similarly for comparison. Then, Nd-doping effects on ferroelectric and photovoltaic properties were evaluated. Polarization-induced photovoltaic effects were observed in both the BFO and BNF solar cell structures with top and bottom electrodes under intense laser illumination. Using Au top electrodes, enhanced photovoltaic properties were observed in the BNF cell compared with the BFO cell. To improve the photovoltaic properties of the BNF cell, instead of the Au top electrodes, In-Sn-O (ITO) top electrodes were employed for the BNF cell. As a result, the photovoltaic properties were found to be markedly improved, resulting in an open circuit voltage of 0.81 V and a short circuit current density of 12.1 mA/cm 2 .

Energy Band Gap Modulation in Nd-Doped BiFeO3/SrRuO3 Heteroepitaxy for Visible Light Photoelectrochemical Activity

“…It was found that the light absorption of the BNFO(100) pc sample has dramatically enhanced in the visible light region (Figures 2c and S2a), although the band gap of BNFO (2.7 eV) is slightly increased compared to that of the BFO sample (2.5 eV), as shown in Figure S2b. A similar band gap of BNFO film was reported by Ukai et al 6 The ΔE VBO of BNFO also enhances, indicating a decrease in conduction band offset (ΔE CBO ) at the heterojunction interface. Thus, the charge transfer efficiency of the BNFO(100) pc sample has been improved.…”

“…5 Besides, BFO has opened up a great research opportunity for the development of water splitting technology due to its lead-free nature, 6 high stability, 7 large saturation polarization (∼90 μC/cm 2 ), 8 and small energy band gap (2.1−2.7 eV) 9 compared with other multiferroic materials. The relatively small energy band gap increases the optical absorption efficiency of BFO in the visible light region 6,9 and thus enhances its ability as a visible light driven photocatalyst because almost 50% of the incoming solar energy is occupied by visible radiation. 10 Moreover, BFO has the advantages of provoking the efficiency of electron−hole pair separation and surface potential modification via manipulating the ferroelectric polarization.…”

“…17−19 Chang et al 17 proposed that the Nd substitution in BFO can reduce the FeO 6 octahedral distortion with increasing anisotropy of Bi/Nd−O bonds and thus helps in improving leakage current. Meanwhile, Ukai et al 6 showed that improved leakage current can be achieved through Nd substitution on the Bi sites to reduce the Bi deficiency in BFO, leading to increased photovoltaic properties. To date, most of the reported multiferroic materials are related to photovoltaic (PV) system.…”

“…Bismuth ferrite (BiFeO 3 , denoted as BFO) is one of the most promising and well-studied multiferroic materials due to its outstanding properties. − It is the only single-phase multiferroic material that exhibits ferroelectric ( T C = 825 °C) and antiferromagnetic ( T N = 370 °C) ordering simultaneously well above the room temperature . Besides, BFO has opened up a great research opportunity for the development of water splitting technology due to its lead-free nature, high stability, large saturation polarization (∼90 μC/cm 2 ), and small energy band gap (2.1–2.7 eV) compared with other multiferroic materials. The relatively small energy band gap increases the optical absorption efficiency of BFO in the visible light region , and thus enhances its ability as a visible light driven photocatalyst because almost 50% of the incoming solar energy is occupied by visible radiation .…”

Remarkably enhanced photovoltaic effects and first-principles calculations in neodymium doped BiFeO3

“…The density-functional-theory (DFT) calculation and X-ray absorption spectroscopy revealed that the A-site rare-earth lanthanum (La) doping in BFO can reduce the leakage current18. It has been reported that doping can be one of the most effective methods used to improve ferroelectric and magnetic properties19202122, as the Bi-site substitution can effectively control the volatility of Bi atoms with reduction of oxygen vacancies23 and enhancement of photovoltaic effects242526. For photovoltaic applications, the BFO should be able to absorb as much light as possible to generate a photocurrent, which requires a lower band gap and large absorption coefficient27.…”