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High-quality epitaxial BiFeO3 (BFO) films were grown on (001)-, (110)- and (111)-oriented Nb:SrTiO3 (NSTO) substrates by pulsed laser deposition. The type of domain structure can be modulated using BFO ferroelectric films with different crystalline orientations. The ON/OFF ratios obtained in (001)-, (110)- and (111)-oriented Au/BFO/NSTO ferroelectric tunnel junctions (FTJs) are 6 × 103, 3 × 104 and 2 × 105, respectively. Analysis of the I – V curves of tunnelling current and average BFO ferroelectric barrier height proves that the polarization intensity of the BFO films modulates both the ferroelectric barrier and the Schottky barrier profile, which further influences the electronic tunnelling probability in BFO FTJs. This work will be useful for further study on achieving a giant ON/OFF ratio and developing insights into the barrier profile and transport mechanism of metal/ferroelectric/semiconductor-type FTJs. [ABSTRACT FROM AUTHOR]

In this work, we report the effectively enhanced tunneling electroresistance effect in Au/(SrTiO3)2/(BaTiO3)4/(CaTiO3)2/Nb:SrTiO3 superlattice ferroelectric tunnel junction (FTJ). The stable polarization switching and enhanced ferroelectricity were achieved in the nanoscale thickness high-quality epitaxial superlattice. A high ON/OFF current ratio of more than 105 was obtained at room temperature, which is an order of magnitude larger than the BaTiO3 FTJ with the same structure. Nonvolatile resistance switching controlled by nonvolatile polarization switching was observed in the superlattice FTJ. Driven by increased polarization and intrinsic asymmetric ferroelectricity, a highly asymmetric depolarization field is generated compared with the Au/BaTiO3/Nb:SrTiO3 FTJ, resulting in an enhanced tunneling electroresistance effect. These results provide a potential way to construct FTJ memory devices by constructing asymmetric three-component ferroelectric superlattices. [ABSTRACT FROM AUTHOR]

In this work, we demonstrated the large-area film growth of all-inorganic perovskite CsPbBr3 with semiconductor industry compatible radio frequency magneton sputtering technology. This approach avoids the use of toxic organic solvents, which are required extensively for the solution growth process of these perovskite films. Even on ordinary glass substrates, the CsPbBr3 film of 100 cm2 with a single phase and ultra-smooth surface can be grown under optimized sputtering conditions, among which the substrate temperature is proved very important. Temperature-dependent photoluminescence spectra and femtosecond transient absorption spectra studies show that no subband defect levels are observed in such perovskite films. The temperature-dependent resistivity measurement exhibits a typical thermally activated electrical behavior, and a bandgap of 2.24 eV is obtained, which is consistent with the optical measurements. Therefore, both the optical and electrical studies indicate that the CsPbBr3 film with high optical quality can be grown with effective one-step sputtering technology. [ABSTRACT FROM AUTHOR]

All-inorganic perovskite CsPbX3 nanocrystals (NCs) have made remarkable achievements in optoelectronic applications due to their enhanced stability, low-cost, easy-to-perform synthetic routes, broad emission spectra tunability, and high photoluminescence quantum yields, especially for light emitting diodes (LEDs) and solar cells (SCs). In this perspective, the structure and optoelectronic properties of CsPbX3 NCs are reviewed, and the recent research progresses in LEDs and SCs are presented. Finally, a brief outlook of this field is proposed to point out some important challenges and possible solutions. [ABSTRACT FROM AUTHOR]

The synthesis of CsPbX3 perovskite nanocrystals (NCs) has made remarkable progress with the growing demand for various optoelectronic applications. Obtaining CsPbX3 NCs through a detectable approach is a challenging topic. Herein, a noninjection synthesis strategy for CsPbX3 NCs with different morphologies is reported, which brings slow dynamics and simple operation. So, the evolution of NCs can be detected by spectroscopy, which is fundamental to understanding and manipulating the growth process. The nanocubes, nanowires, and encapsulated NCs obtained by this approach enable a broad range of future endeavors in display, laser arrays, and underwater optoelectronic devices, respectively. [ABSTRACT FROM AUTHOR]

Ferroelectric domain is an elusive feature on bulk photovoltaic effect and can be tuned by the growth conditions. Here, in (111)‐oriented BiFe1−xCoxO3 epitaxial films, the periodic ferroelectric domains structure is manipulated by Co‐doped concentration. The intrinsic 109° domain structure is turned into 71° domain structure due to reduction of crystal cell volume. The experimental results show that ferroelectric domain and ferroelectric domain wall (DW) play completely different roles in bulk photovoltaic effect. In ferroelectric domain structure, the domain provides a depolarization field for the separation of photogenerated carriers and DW is carriers transport channel. The 71° ferroelectric domain creates a larger depolarization field than the 109° domain, which leads to open‐circuit voltage exceeding 1.7 V. Besides, the 71° domain wall has a higher photoconductivity than the 109° domain wall, which makes short‐circuit current density reaching 0.42 mA cm−2. The optimization of domain structure will effectively enhance bulk photovoltaic effect and also provides a new method to regulate the domain structure for bulk photovoltaic devices. [ABSTRACT FROM AUTHOR]