The CHNHPbI perovskite solar cells have been fabricated using three-porous-layered electrodes as, 〈glass/F-doped tin oxide (FTO)/dense TiO/porous TiO-perovskite/porous ZrO-perovskite/porous carbon-perovskite〉 for light stability tests. Without encapsulation in air, the CHNHPbI perovskite solar cells maintained 80% of photoenergy conversion efficiency from the initial value up to 100 h under light irradiation (AM 1.5, 100 mW cm). Considering the color variation of the CHNHPbI perovskite layer, the significant improvement of light stability is due to the moisture-blocking effect of the porous carbon back electrodes. The strong interaction between carbon and CHNHPbI perovskite was proposed by the measurements of X-ray photoelectron spectroscopy and X-ray diffraction of the porous carbon-perovskite layers.

Single-domain BFO thin films are prepared on a SrRuO3-buffered SrTiO3 (STO) (001) substrate by RF planar magnetron sputtering. A domain structure is controlled by vicinal direction of the STO substrate. The BFO thin films on vicinal STO along <110> show single-domain structure without any domain walls. To confirm the influence of epitaxial strain on lattice distortion and ferroelectricity, single-domain BFO thin films with thicknesses ranging from 10–1000 nm are prepared. Synchrotron X-ray diffraction reveals that lattice relaxation and step bunching occur in the thickness range of 50–200 nm. The BFO films with thicknesses over 300 nm are almost free from the influence of the epitaxial strain induced by (001)-oriented substrates. The remanent polarization P r is almost constant at about 60 µC/cm2. However, P r slightly increases in the BFO films with thicknesses less than 200 nm. Even the 100-nm-thick BFO film show fully saturated D–E hysteresis at RT, and the P r is 65 µC/cm2.

Epitaxial BiFeO 3 (BFO) thin films with striped-and single-domain structures have been grown on SrTiO 3 (STO) ( 103) and ( 113) substrates by radiofrequency planar magnetron sputtering. The domain structure of BFO was controlled by the orientation of the STO substrate. Piezoelectric force microscopy revealed that BFO thin films on STO (103) and STO (113) had a striped-domain structure with 71°domain walls running along o010p STO , and a single-domain structure, respectively. To confirm the photovoltaic property, rectangular Pt electrodes with widths of 150-200 µm were deposited on BFO surfaces with interelectrodes distances of 200-250 µm. I-V characteristics were measured under an illumination of a collimated violet laser (λ = 405 nm) with a power density of 380 W/cm 2 . In the striped-domain-structure BFO film with Pt electrodes fabricated along domain walls, above-band-gap open-circuit voltage (V OC ) of 29 V was observed. In addition, single-domain-structured BFO thin film with Pt electrodes fabricated along h 110i also showed above-band-gap V oc of 26 V despite the absence of domain walls. It is considered that these largeV oc values originated from the photovoltaic effect not at the domain walls but in bulk BFO.

O 3 (BFZO) thin films have been prepared on Pt/TiO 2 /SiO 2 /Si substrates by pulsed laser deposition, and their ferroelectric and ferromagnetic properties have been characterized. X-ray diffraction (XRD) patterns of BSFO and BFZO thin films show a peroveskite single phase and BSFO thin films show shifting and splitting of peaks with increasing fraction of Sr. The BFZO thin film shows a lower leakage current than the BFO thin film and their P-E and M-H hysteresis loops are obtained. The XRD peaks of BSFZO thin films also shift to an angle lower than that of BFO thin films. The P-E hysteresis loop is obtained at 80 K and the reamanent polarizations of the Bi 1:1 Sr x Fe 0:9 Zn 0:1 O 3 thin film are 79 and 58 mC/ cm 2 for x ¼ 0:05 and 0.1, respectively. The M-H hysteresis loop is also obtained at 80 K and the reamanent magnetization and coercive field are 1.1 and 6 emu/cm 3 , and 222 and 792 Oe at a maximum magnetic field of 10 kOe for x ¼ 0:05 and 0.1, respectively.