Mutual regulation of polarization and magnetization in BFCNT/BFCO heterostructure via stress analysis of dipoles

Regulation of Photovoltaic Response in ZSO-Based Multiferroic BFCO/BFCNT Heterojunction Photoelectrodes via Magnetization and Polarization

“…The corresponding Tauc plots, in which the optical absorption coefficient (α) relates to bandgaps ( E g ) via Planck’s constant ( h ) and the frequency of the incident photon (υ) as α = ( h υ – E g ) 1/2 , where h υ is the photon energy ( E ), can be calculated from the absorption curves. Assuming that BFCO, BFCNT, and ZSO present a direct allowed bandgap, bandgaps of 1.62, 1.74, and 3.1 eV are evaluated, respectively, which are in agreement with the previous reports. ,, The inset in Figure d displays the band edge positions of each layer analyzed employing UPS measurements. It is worth noting that only UPS results based on ordered domain BFCO and BFCNT were analyzed qualitatively due to the complexity of the coexistence of ordered/disordered phases in both BFCO and BFCNT films, thus making the construction of the energy band diagrams challenging.…”

“…It can be concluded from the unit cell structures of both BFCO and BFCNT presented in Figure 1a that five corner-sharing BO 6 (B = Fe, Co, Ni, and Ti) octahedra-based perovskite-like layers are sandwiched by two fluorite-like (Bi 2 O 2 ) 2+ layers, thus forming an AU-typed bismuth layer perovskite BFCNT, 19 but for BFCO, it is more like an alternating arrangement of FeO 6 and CrO 6 octahedra layer along the [111] orientation. 15 SEM images after chemical etching (the insets in Figure 1d) showed that the crystal grains of BFCNT pile layer after layer, forming a typical bismuth layer perovskite, but the BFCO grains usually gather together in the manner of a tetragonal structure.…”

“…Assuming that BFCO, BFCNT, and ZSO present a direct allowed bandgap, bandgaps of 1.62, 1.74, and 3.1 eV are evaluated, respectively, which are in agreement with the previous reports. 18,19,23 The inset in Figure 2d displays the band edge positions of each layer analyzed employing UPS measurements. It is worth noting that only UPS results based on ordered domain BFCO and BFCNT were analyzed qualitatively due to the complexity of the coexistence of ordered/disordered phases in both BFCO and BFCNT films, thus making the construction of the energy band diagrams challenging.…”

“…), thus decreasing E g effectively. Cr doping of BFO results in a representative double-perovskite Bi 2 Fe 2 O 6 (BFCO) − with different amounts of Fe–Cr cationic disorder, providing E g in a range of 1.4–2.4 eV. , For Fe, Co, and Ni co-doped Aurivillius (AU) compounds Bi 6 Fe 2– x Co x /2 Ni x /2 Ti 3 O 18 (0 ≤ x ≤ 1), the E g varies with x in a range of 1.28–2.12 eV; especially when x = 0.4 eV (Bi 6 Fe 1.6 Co 0.2 Ni 0.2 Ti 3 O 18 , BFCNT), E g can be as small as 1.58 eV, which is extremely close to the optimal E g = 1.5 eV for single-junction solar cells, meeting the requirements for active layers in solar photovoltaic devices. However, the conversion efficiencies of these photovoltaic devices are still low but could exceed theoretically the Shockley–Queisser limit …”

Multiferroic oxide BFCNT/BFCO heterojunction black silicon photovoltaic devices

“…For Aurivillius (AU) compound Bi 6 Fe 2−x Co x/2 Ni x/2 Ti 3 O 18 (0 ≤ x ≤ 1), E g varies with x, especially when x = 0.4 eV (Bi 6 Fe 1.6 Co 0.2 Ni 0.2 Ti 3 O 18 , BFCNT), the E g can be as small as 1.58 eV, etc. [11][12][13] . Although the efficiency of these solar cells is still low owing to the poor overall conduction caused by their large bandgap and intrinsic dielectric properties, these ferroelectric photovoltaic devices empower with the potential to exceed the Shockley-Queisser limit, theoreticlly 14 .…”